Rifle Scopes March 4.5-28x52 High Master Review and Comparison to Tangent Theta 5-25x56

SAR421

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One other question that just occurred to me. Was any time spent looking at the optical quality at a nearly maxed erector?

The March with 30 MILs of elevation should in theory be able to handle up to about 50 MOA (14.8 MILs) base and still be zeroed at 100y. Was there any perceivable change in optical quality as it neared the limits of the erector? Out of the 30 MILs total travel how many were usable? On some optics the Zero Stop takes away from the usable MILs, is this the case with the March?
 

Glassaholic

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    Can anyone explain why this is so?
    There is the long explanation and the short one, I'll offer up the short one. Parallax is the alignment of the reticle on the object you are aiming at. The scope is stationary but you move your head position slightly and you notice that the reticle has now moved slightly off target - parallax needs to be adjusted so the reticle does not move for your given target. There is another name for the parallax adjustment and it is called "focus" but focus has to do with what "looks in focus" to your eye and while the two should align they do not always; therefore, it is important that you adjust your "focus" to eliminate as much parallax as possible for your given target and not simply to make sure your target looks in focus. This is where scopes that have a "forgiving" parallax have an advantage here as you can essentially set it and forget it. The Tangent is essentially known for this, if you are shooting a course where you have targets between 300-1000 you can set the Tangent to around 500ish and almost everything is in focus and parallax free.
    Could DOF effect this? Since the image is changed over the course of its path. At least parallax can be used to see the mirage at the middle of the distance.
    I believe it can have an effect; however, I will defer to @koshkin for a more thorough explanation.
     

    Glassaholic

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    One other question that just occurred to me. Was any time spent looking at the optical quality at a nearly maxed erector?

    The March with 30 MILs of elevation should in theory be able to handle up to about 50 MOA (14.8 MILs) base and still be zeroed at 100y. Was there any perceivable change in optical quality as it neared the limits of the erector? Out of the 30 MILs total travel how many were usable? On some optics the Zero Stop takes away from the usable MILs, is this the case with the March?
    I'm glad you asked that because I did indeed check for this and meant to write about it (I will update my review above). With elevation maxed out at the top of travel, I compared both scopes at 15x magnification and both exhibited excellent IQ, I would have no issues using either maxed out on elevation.
     

    Denys

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    There is the long explanation and the short one, I'll offer up the short one. Parallax is the alignment of the reticle on the object you are aiming at. The scope is stationary but you move your head position slightly and you notice that the reticle has now moved slightly off target - parallax needs to be adjusted so the reticle does not move for your given target. There is another name for the parallax adjustment and it is called "focus" but focus has to do with what "looks in focus" to your eye and while the two should align they do not always; therefore, it is important that you adjust your "focus" to eliminate as much parallax as possible for your given target and not simply to make sure your target looks in focus. This is where scopes that have a "forgiving" parallax have an advantage here as you can essentially set it and forget it. The Tangent is essentially known for this, if you are shooting a course where you have targets between 300-1000 you can set the Tangent to around 500ish and almost everything is in focus and parallax free.

    I believe it can have an effect; however, I will defer to @koshkin for a more thorough explanation.
    What you are talking about is known as the hyperfocal distance. It's not unique to the TT and I certainly do not understand why one brand of scopes would be "known" for this effect versus another brand.

    Essentially what you described is finding the focus distance at which the DOF will be greatest for your purposes. This distance can be calculated for a camera lens (there are many online calculators for this) but I have not found any for riflescopes. The formula involves focal length, aperture (f/stopor f-number) and desired size for the circle of confusion. The first two figures are not known for riflescopes. My belief if that the focal length and aperture of the objective lens group is what is needed here and then you can play the the CoC to match the magnification generated by the erector. I would think that a CoC value of .02 mm would be needed for zoom ratios past 3-4X.

    For our application, I like your quick'n dirty method: Figure out the minimum and maximum distance that you need to have in focus and set the focus at an intermediate distance between the 2 distances but closer to the nearer distance as DOF extends much further behind than in front of the target (focus point) especially as the distance to target increases.
     

    Jefe's Dope

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    Great review. Do you have one for the Kahles 525i?
     

    Glassaholic

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    There is also the ability to use 2 rings in the middle. Like 2 NF Ultralite 4 bolt or 2 ARCM10's.
    That is correct, here's a pic I took with two ARC's together, should be pretty darn strong
    20210410_March_Shorty_1-10x24_AudereMount_ 001.jpg
     
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    Glassaholic

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    Great review. Do you have one for the Kahles 525i?
    I do not, the original K525i did not have much interest for me because of the narrow FOV and IQ falloff above 20x (reported); however, the new DLR version does pique my interest quite a bit with it's wide FOV and apparently fixed IQ issues. I did a review years ago of the K624i when the SKMR series reticles were first introduced (back when Jeff Huber was working with Kahles before he started ZCO) and while I loved most everything about that scope I was highly disappointed in the heavy CA that was visible in multiple situations. It is my understanding the K525i series has toned down the CA so that would be good. I am not a huge fan of the SKMR reticles with the thick horizontal lines of the Christmas tree, but it's not as bad as a Horus so I give it that.

    Would be great to get hold of a ZCO 5-27 and Kahles K525i DLR before I get rid of my Tangent Theta...
     
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    Glassaholic

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    Would be great to get hold of a ZCO 5-27 and Kahles K525i DLR before I get rid of my Tangent Theta...
    I have someone willing to lend me their ZCO, anyone around Denver area willing to lend me their Kahles DLR for a couple days? Where's @bjay , he usually has a bunch of these sitting around :D
     
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    Krob95

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    didn’t see you had a zco already lined up lol
     

    Baron23

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    There is the long explanation and the short one, I'll offer up the short one. Parallax is the alignment of the reticle on the object you are aiming at. The scope is stationary but you move your head position slightly and you notice that the reticle has now moved slightly off target - parallax needs to be adjusted so the reticle does not move for your given target. There is another name for the parallax adjustment and it is called "focus" but focus has to do with what "looks in focus" to your eye and while the two should align they do not always; therefore, it is important that you adjust your "focus" to eliminate as much parallax as possible for your given target and not simply to make sure your target looks in focus. This is where scopes that have a "forgiving" parallax have an advantage here as you can essentially set it and forget it. The Tangent is essentially known for this, if you are shooting a course where you have targets between 300-1000 you can set the Tangent to around 500ish and almost everything is in focus and parallax free.

    I believe it can have an effect; however, I will defer to @koshkin for a more thorough explanation.
    I still don’t get it. If you ocular is properly and accurately adjusted to bring the reticle into best focus, and the parallax is properly and accurately adjusted to bring the target into best focus, the reticle and target are on the same focal plane and there should be no parallax errors.

    im
    Utterly willing to be wrong so can you explain the flaw in my thinking above?

    thank you
     

    Urraynium

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    Great review.

    How did you like the March on the MDRx?

    I have a Kahles K18i on a 6.5 CM MDRx which works great but looking for a bit more scope for it.

    Thanks
     

    Glassaholic

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    Great review.

    How did you like the March on the MDRx?

    I have a Kahles K18i on a 6.5 CM MDRx which works great but looking for a bit more scope for it.

    Thanks
    For my purposes with the MDRx it was too much scope, but it worked perfectly well on the short rig. Right now I have the March Shorty 1-10 on the MDRx and really like that combo a lot.
     

    Glassaholic

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    I still don’t get it. If you ocular is properly and accurately adjusted to bring the reticle into best focus, and the parallax is properly and accurately adjusted to bring the target into best focus, the reticle and target are on the same focal plane and there should be no parallax errors.

    im
    Utterly willing to be wrong so can you explain the flaw in my thinking above?

    thank you
    I completely forgot about your question Baron, apologies. To put it simply, in a perfect world, yes, all this should work out, but we don't live in a perfect world and not everything in a scope is "perfectly" aligned which introduces errors, they may be slight but they are errors nonetheless. Scopes that have forgiving DOF also tend to have forgiving parallax, not sure if that is coincidence or if there is some relationship there (@koshkin may be able to explain better). I'll also point out your comment, "If you ocular is properly and accurately adjusted" and say that many do not "properly and accurately" adjust the diopter to their eyes, and many of the issues/errors we hear about, I believe, are due to this because all our eyes are different and a scope adjusted for one shooter may be off enough for another for them to feel like that scope is a poor performer when in reality it was simply because the diopter was not adjusted properly for their eye.
     
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    Baron23

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    I completely forgot about your question Baron, apologies. To put it simply, in a perfect world, yes, all this should work out, but we don't live in a perfect world and not everything in a scope is "perfectly" aligned which introduces errors, they may be slight but they are errors nonetheless. Scopes that have forgiving DOF also tend to have forgiving parallax, not sure if that is coincidence or if there is some relationship there (@koshkin may be able to explain better). I'll also point out your comment, "If you ocular is properly and accurately adjusted" and say that many do not "properly and accurately" adjust the diopter to their eyes, and many of the issues/errors we hear about, I believe, are due to this because all our eyes are different and a scope adjusted for one shooter may be off enough for another for them to feel like that scope is a poor performer when in reality it was simply because the diopter was not adjusted properly for their eye.
    Hi my friend - wow, thank you for following up and reaching out.

    Yeah, I get it...perhaps I should have said "theoretically, if both the reticle and the target are in perfect focus, then both with be by definition on the same focal plane and there would be no parallax errors"

    Emphasis on "theoretically" and "perfect focus" haha

    I get what you are saying but it does seem that, aside from errors in execution, if the reticle and target are in best focus, then this would indeed put them both on the same plane and eliminate parallax error (or damn close to it).

    I do put some attention into focusing my ocular and parallax adjustment for clarity but then do the small head movement to ensure that there is no movement between the two.

    Thanks again and yes, this is far from a perfect world and we shooters are far from perfect humans. :)
     
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    D_TROS

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    Awesome review as usual. Good to see you finally got a TT. They are phenominal. I really like the extra wide turret sleeve to slid ove the top. I actually had a couple for my old 5-40 march.

    Biggest complaint with TT, ZCO and S&B is the closeness of the clicks makes it hard to read. Hate that. The clicks are fantastic just too close and found myself going past quite often.


    Im having a one day borderwars match on Aug 28th east of Denver 1.5 hr you should come. I would like to see this scope.

    I have shot alot of PRS matches with the March 5-40. Not as many with the TT. Ive sold most my high end stuff to start outfitting my son for shooting. His 223 barreled action arrived yesterday.

    Anyway, still looking forward to a range day with you.

    Regards
    DT
     

    Urraynium

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    For my purposes with the MDRx it was too much scope, but it worked perfectly well on the short rig. Right now I have the March Shorty 1-10 on the MDRx and really like that combo a lot.
    Thanks for the feedback. Based on the reviews that you and others have made on the Hide I think I will be waiting for the new March 1-10 tree reticle to try that out.
     
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    Glassaholic

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    Awesome review as usual. Good to see you finally got a TT. They are phenominal. I really like the extra wide turret sleeve to slid ove the top. I actually had a couple for my old 5-40 march.

    Biggest complaint with TT, ZCO and S&B is the closeness of the clicks makes it hard to read. Hate that. The clicks are fantastic just too close and found myself going past quite often.


    Im having a one day borderwars match on Aug 28th east of Denver 1.5 hr you should come. I would like to see this scope.

    I have shot alot of PRS matches with the March 5-40. Not as many with the TT. Ive sold most my high end stuff to start outfitting my son for shooting. His 223 barreled action arrived yesterday.

    Anyway, still looking forward to a range day with you.

    Regards
    DT
    Wish I could, but we are moving that weekend, heading out to Florida 😞. Trying to fit in one last shoot here in Colorado but don’t know when that will be yet.
     
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    ormandj

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    Thank you for putting together this review. I'm surprised at how closely you rated this scope in many optical categories to the TT.

    How's the 4.5-28 compare to the latest March 5-42, if you've had time behind it? I was not impressed with the optical quality on the 5-42 compared to my ZCO/TT scopes, but you indicate this one is close. The 5-42 wasn't bad by any means, but the DOF and need to constantly fiddle with parallax wasn't my cup of tea for the types of shooting I do. Same with CA - to which I am particularly sensitive. The blurring at the wider angles, as you noted, will likely not bother many people, and the extra FOV was worth it to me - but I felt there was a missing crispness except at the VERY center of the 5-42 compared to ZCO/TT.

    It seems like this scope may have many of the advantages of the 5-42 without the downsides. I'm hoping these scopes with more reasonable magnification range have less optical tradeoffs. I was blown away with how nice the turrets were, and definitely liked the weight (or lack thereof), I just couldn't get comfortable behind the scope after being spoiled with ZCOs and TTs.

    Are there any sellers of March scopes that accept returns for unmounted scopes at this point? I'd be willing to try a few more out, but not without an easy exit strategy, and nobody local (or even within 300 miles) carries them, so in-person isn't possible. Thank you again for the review, I'm pleasantly surprised with how well this scope has performed.
     

    Glassaholic

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    Thank you for putting together this review. I'm surprised at how closely you rated this scope in many optical categories to the TT.

    How's the 4.5-28 compare to the latest March 5-42, if you've had time behind it? I was not impressed with the optical quality on the 5-42 compared to my ZCO/TT scopes, but you indicate this one is close. The 5-42 wasn't bad by any means, but the DOF and need to constantly fiddle with parallax wasn't my cup of tea for the types of shooting I do. Same with CA - to which I am particularly sensitive. The blurring at the wider angles, as you noted, will likely not bother many people, and the extra FOV was worth it to me - but I felt there was a missing crispness except at the VERY center of the 5-42 compared to ZCO/TT.

    It seems like this scope may have many of the advantages of the 5-42 without the downsides. I'm hoping these scopes with more reasonable magnification range have less optical tradeoffs. I was blown away with how nice the turrets were, and definitely liked the weight (or lack thereof), I just couldn't get comfortable behind the scope after being spoiled with ZCOs and TTs.

    Are there any sellers of March scopes that accept returns for unmounted scopes at this point? I'd be willing to try a few more out, but not without an easy exit strategy, and nobody local (or even within 300 miles) carries them, so in-person isn't possible. Thank you again for the review, I'm pleasantly surprised with how well this scope has performed.
    Yes, I do have experience with both the 4.5-28 and 5-42. The center resolution of the 5-42 is probably better (I did not have them side by side so just going off memory) but the overall performance of the 4.5-28 is a better experience than the 5-42 IMO. By going down to 6.2x erector March was able to compensate much better for edge to edge sharpness, DOF, eyebox and parallax. The locking turrets on the March 5-42 are the real deal, unfortunately they did not make their way to the 4.5-28 but hopefully March will offer some locking turrets along the same quality as the 5-42 at some point, when that happens I think this scope will be the one to beat for all except the optical purists.
     
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    Denys

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    I should think the center resolution of a 56mm lens will be greater than a 52mm lens when you're comparing at the same magnification, of course. These two riflescopes have the same glass, just different diameter. I would have to check the focal length of the 5-42X56 and calculate its f-number and compare that to the 4.5-28X52. That will tell the story on DOF differences and I agree that a reduced erector ratio will make a difference.
     

    Denys

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    I did some calculations and perhaps this might help. I "measured" the focal length of a 4.5-28X52 and a 5-42X56. Then I calculated their respective F-numbers and finally I created a little spreadsheet with formulas to calculate the hyperfocal distance of each scope and the near distance for the DOF of the hyperfocal distance using a CoC of 0.030. Turns out the 4.5-28X52 has an HD of 227 yards and a near distance of 118 yards. Compare this to the 5-42X56 with an HD of 306 yards and a near distance of 159 yards.

    RiflescopeHyperfocal Distance (yards)HD Near limit (yards)
    March-FX 4.5-28X52227118
    March-FX 5-42X56306159

    So, big deal you say.

    Let's go a little further. Lets calculate the near/far DOF values for 100 yards and 200 yards, for each scope. Values are in yards

    Riflescope100 yds Near Limit100 yds Far Limit200 yds Near Limit200 yds Far Limit
    March-FX 4.5-28X52731781101655
    March-FX 5-42X5680148127576

    As you can see the DOF of the 4.5-28X52 is deeper at 100 and 200 and the difference will keep growing as the focus distance increases. This is the trade off between higher resolution with the larger objective lens versus the deeper depth of field of the smaller objective lens.

    (My measurements and calculations are all mine. Any mistakes in those are mine. I am not a bidet; I own my mistakes. That said, if any mistake is found, I will come back and correct them.)

    Edited to add: If I had the focal length of the TT in this thread, I could calculate those values for that riflescope.
     
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    Denys

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    Denys, some of these numbers are fairly easy to confirm empirically. Take the scopes out and you will see that most of these are wrong.

    ILya
    Hello ILya,

    No, the numbers are not wrong, at least I don't think I made a mistake coding the formulas in Excel and I did sample checking with DOF Master. The numbers I used are all there, you are welcome to reproduce my calculations: I gave you the focal length that I measured for each scope and if that was measured wrong at least I measured them the exact same way. You know the diameter of the objective lens.

    I did state I was using a CoC of 0.030mm for everything. This last one is definitely something that can be argued and modified. I've long asserted that at high zoom values, one should reduce the CoC accordingly and I am a big proponent of a CoC of 0.020 past 3-4X zoom. I can tell you that when I focus my 4.5-28X52 at 200 yards and stay below 15X, the DOF is huge.

    That said, my goal here was not to present guide numbers but to try to answer Bill's question regarding the relationship between length, objective diameter and DOF and I think my numbers tell the story. A smaller objective will produce a deeper DOF. That's the reasoning behind the modifier disk provided by March for many of its top end scopes. But the difference between the 5-42X56 and the 4.5-28X52 to which Bill alluded had the added twist of the 4.5-28X5s having a shorter focal length than the 5-42X56 as well as a smaller diameter objective. One would have thought that reducing both FL and Objective would produce the same DOF for the 4.5-28X52 as the 5-42X56. As the numbers show, in this case, the reduction of the focal length trumped the reduction of the objective length, for the DOF.

    Now, If I change the CoC from 0.030 to 0.020; the 200 yard values change dramatically, as I expect them to: For the 5-42X56, the DOF runs from 145 yards to 354 yards. For the 4.5-28X52; the DOF runs from 130 yards to 483 yards. This is what would would find "empirically" if you were using a higher zoom setting.
     

    Denys

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    Oh, and with a CoC of 0.020, the hyperfocal length for the 5-42X56 is at 459 yards, running from 236 yards to infinity. For the 4.5-28X52, it is 341 yards, running from 175 yards to infinity.
     

    koshkin

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    Hello ILya,

    No, the numbers are not wrong, at least I don't think I made a mistake coding the formulas in Excel and I did sample checking with DOF Master. The numbers I used are all there, you are welcome to reproduce my calculations: I gave you the focal length that I measured for each scope and if that was measured wrong at least I measured them the exact same way. You know the diameter of the objective lens.

    I did state I was using a CoC of 0.030mm for everything. This last one is definitely something that can be argued and modified. I've long asserted that at high zoom values, one should reduce the CoC accordingly and I am a big proponent of a CoC of 0.020 past 3-4X zoom. I can tell you that when I focus my 4.5-28X52 at 200 yards and stay below 15X, the DOF is huge.

    That said, my goal here was not to present guide numbers but to try to answer Bill's question regarding the relationship between length, objective diameter and DOF and I think my numbers tell the story. A smaller objective will produce a deeper DOF. That's the reasoning behind the modifier disk provided by March for many of its top end scopes. But the difference between the 5-42X56 and the 4.5-28X52 to which Bill alluded had the added twist of the 4.5-28X5s having a shorter focal length than the 5-42X56 as well as a smaller diameter objective. One would have thought that reducing both FL and Objective would produce the same DOF for the 4.5-28X52 as the 5-42X56. As the numbers show, in this case, the reduction of the focal length trumped the reduction of the objective length, for the DOF.

    Now, If I change the CoC from 0.030 to 0.020; the 200 yard values change dramatically, as I expect them to: For the 5-42X56, the DOF runs from 145 yards to 354 yards. For the 4.5-28X52; the DOF runs from 130 yards to 483 yards. This is what would would find "empirically" if you were using a higher zoom setting.

    First of all, I apologize that it looks like I am picking on you. I am not. However, you are trying to port calculations from the photography world into this and are making some rather incorrect assumptions. The internet retains everything, so I really want to make sure this is corrected or someone will dig this up a year from now and walk away with all these pseudo-technical half-truths as the holy grail because they sound impressive.

    The numbers are wrong because of the exact things you pointed out: depth of field varies with magnification. The statement when focused at 200 yards "For the 5-42X56, the DOF runs from 145 yards to 354 yards" is completely and utterly meaningless without saying what magnification it is at (however, since you your CoC reasoning is grossly wrong, if it is accurate somewhere that is purely coincidental).

    Depth of field depends on the F-number of the objective lens (ratio of focal length to the objective diameter, assuming that is the aperture stop. You are kinda saying it, but not explicitly unless I missed it. That is an important thing to make clear.

    Objective diameter we know. How exactly did you measure the focal lengths? If you are trying to be rigorous, you should ask March what the focal lengths are. There is no way I can think of to measure it exactly without talking to the designer of the scope, or taking the whole thing apart and doing some measurements. You do not know where exactly the FFP is located. It is not always right under the turrets. Also, March has used a somewhat complicated objective design in the past, at least once that I can think of, where even if you knew exactly where the FFP was you would not be able to figure out the focal length. I do not know if March is OK with the exact focal lengths of their objectives published, but you can ask if you want to be serious about it. If I was them, I would probably not release it. From a competitive info standpoint, a couple of numbers like that and I can figure out all sorts of stuff about the internals of a scope.

    Another point: how do you know the erector system is not limiting the DOF at one of the portions of the magnification range? Those lens systems have F-numbers too.

    Finally, your CoC assumption copied over directly from the photography books can only be correct by accident.

    If you really want to figure out the CoC, you need to map the resolution limit of the human eye, via the eyepiece and the erector, onto the FFP. That will give you a CoC that is likely different at every magnification if the objective is indeed the limiting factor here.

    Standard photographic CoC assumptions absolutely and unequivocally do not apply to riflescopes.

    If you really want to figure this out in a somewhat rigorous matter and if March is comfortable with you releasing the focal length numbers (I sure as hell will not be releasing them), you can calculate appropriate CoC to a reasonable degree from a set of uncomplicated empirical measurements.

    Set up both scope at the closest or thereabouts focusing distance on a range where you know distances with great granularity and physically measure the DOF at each marked magnification.

    From that, you can figure out appropriate COCs and extrapolate the rest numerically. The results will be accurate for your eyes, but if you have reasonably healthy eyes it should be close to most other people.

    If you really want to get to the bottom of this, you should also repeat the measurements in low light when your eye pupil is dilated.

    Now, onto the good part: while quantitatively, there is definitely some work to do here, qualitatively, you are absolutely correct.

    Here is a brief history of how the 4.5-28x52 design came to life:

    I was testing a prototype 5-42x56 for March and I also had the 3-24x52 on hand. I thought that new 5-42x56 March absolutely kicked ass, but turrets could be a little different (that's how we ended up with the new locking turrets) and that there was also room for a smaller scope between the 5-42x56 and 3-24x52. That could also be an interesting opportunity for March to have a riflescope with a little more depth of field, and somewhat different erector optimization that more traditional March designs.

    I reached out to March with a few suggestions that are mostly proprietary, but one of them was: if you dialed back on erector ratio a little and optimized it to be as good as humanly possible between 15x and 20x (which is there I do a lot of shooting), what could you come up with?

    The 4.5-28x52 is what they could come up with and it is really excellent.

    Fast forward to today and when I look around my office, there are two early production 5-42x56 March scopes within arms reach, one early 4.5-28x52 and they are building another one for me. For what it is worth, I also still have that 3-24x52 on a large frame AR. As I said these are really nice scopes.

    To be clear, there were other people providing feedback to March. It wasn't just me. However, I was in those conversations and the request for the 4.5-28x52 or something along those lines came from steel shooters.

    ILya
     

    Denys

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    Hello ILya, please do not apologize; I do not feel picked on in any way. Au contraire< I am always looking to learn more and I appreciate the corrections you provide.


    Now to answer a few of your questions or comments.


    1- The formula for calculating DOF does not include magnification. I play with the CoC value, adjusting it for magnification as I explained. My picking 0.030 was originally from my photography experience, but I have since found out it works for riflescopes as well, at least as a starting value a low magnification. A happy coincidence? Perhaps. But the CoC range I use is proper.


    2- DOF is definitely dependent of focal length and F-number. I mention that several times in my earlier post, in different ways. I even take the time to discuss the use of the modifier disk that March includes with many of their riflescopes with 52 and 56mm objectives. The reducing on the aperture is equivalent to one full stop, boosting the DOF greatly.


    3- In the other thread where I first discussed the possibility of calculating the DOF of various scopes, I spent quite a bit of time explaining that in order to even attempt that, one needs to have the focal length of the objective lens group. I also stated that no riflescope manufacturer provides that information and that most (probably all) consider it company-proprietary information. This is when I explained how I was figuring it out and that it could only be used as approximation, a guide, if you will. This is the reason I used scare quotes in my post when I said I “measured” the focal length of the two scopes. I would never reveal proprietary information.


    However, all that said, I take your comments about how trying to even measure that without opening a scope, is pretty much a waste of time as different scope probably have different placements for the FFP, certainly across brands and makers. That was why I was talking about a standard way to measure it for all scopes, but now I think that would just be misleading and create confusion.
     

    Denys

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    Yea, was wondering if it is designed the same way as 5-42 is. I have already put an order for one but I am still a little bit hesitant :)
    The side focus knob on the March-FX 5-42X56 is different from the one on the March-FX 4.5-28X52. The one for the 5-42X56 was designed to be lockable by pushing in/pulling out the the outer knob housing and that is a first for March. The knob of the 4.5-28X52 is the standard knob used on other March riflescopes and if you have the illuminated model, it comes with a 6-position illumination module. You can easily select the level of illumination you want and when you press the middle of the knob, the illumination come on at that level. Press it again, and the illumination turns off. The 4.5-28X56 also comes with a middle wheel that you can attach to the side focus knob. This wheel make it even easier to set the side focus and provides for added granularity when adjusting it. I like a bigger side focus knob because of my arthritis in my left hand, but others without that affliction also like it because of the boost in fine control.

    This riflescope also come with a knob cover that you can attach to the elevation knob. It makes that knob bigger and has big numbers on it, making it easy to read for folks with bifocals or other vision issues up close.
     
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    koshkin

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    Hello ILya, please do not apologize; I do not feel picked on in any way. Au contraire< I am always looking to learn more and I appreciate the corrections you provide.


    Now to answer a few of your questions or comments.


    1- The formula for calculating DOF does not include magnification. I play with the CoC value, adjusting it for magnification as I explained. My picking 0.030 was originally from my photography experience, but I have since found out it works for riflescopes as well, at least as a starting value a low magnification. A happy coincidence? Perhaps. But the CoC range I use is proper.


    2- DOF is definitely dependent of focal length and F-number. I mention that several times in my earlier post, in different ways. I even take the time to discuss the use of the modifier disk that March includes with many of their riflescopes with 52 and 56mm objectives. The reducing on the aperture is equivalent to one full stop, boosting the DOF greatly.


    3- In the other thread where I first discussed the possibility of calculating the DOF of various scopes, I spent quite a bit of time explaining that in order to even attempt that, one needs to have the focal length of the objective lens group. I also stated that no riflescope manufacturer provides that information and that most (probably all) consider it company-proprietary information. This is when I explained how I was figuring it out and that it could only be used as approximation, a guide, if you will. This is the reason I used scare quotes in my post when I said I “measured” the focal length of the two scopes. I would never reveal proprietary information.


    However, all that said, I take your comments about how trying to even measure that without opening a scope, is pretty much a waste of time as different scope probably have different placements for the FFP, certainly across brands and makers. That was why I was talking about a standard way to measure it for all scopes, but now I think that would just be misleading and create confusion.

    I'll give it one more shot before giving up.

    To re-iterate: CoC is different at EVERY magnification if you want to model it.

    Photography DOF calculator does not include magnification because outside of Macro world, there is no reasonable concept of magnification with photographic lenses. When we are within the farfield approximation, magnification is only a relevant thing with DVOs.

    Photography DOF calculator assumes a standard eyeball and a couple of standard film formats printed to a specific size as the defining parameters for the CoC. A little off-topic, but that only makes sense when working with film. Even with digital cameras, CoC should really be defined in terms of pixel pitch, since printing to standard A4/letter paper is not terribly common any more.

    With riflescopes, since there is no paper and no image sensor, the CoC is a function of the human eye, eyepiece parameters an erector system parameters. Basically, everything between the brain and the FFP of a riflescope.

    That is why you have to calculate CoC as a function of the magnification setting.

    As a practical consideration, for conventional precision riflescopes, I do not think I have ever run into a question on the depth of field at low magnifications. It is pretty much always sufficient. It is pretty much always brought up when we are talking about mid-to-high magnification.

    Edited to add: since we are talking about March scopes, one of the main criticisms of the original 3-24x52 March was the shallow depth of field. However, that only really becomes prominent above 15x or so. Below 15x, it is really not an issue. The new 4.5-28x52, however, really improves the depth of field by a significant margin compared to the older designs.

    ILya
     
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    Denys

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    Excellent. Thanks for confirming my thinking. I was adjusting the CoC to match the zoom setting, and I specified that I was using 0.020 after 3X on the zoom. I also kept thinking that at high zoom setting, I need to further reduce the CoC accordingly, especially in zoom ratios like 6X, 8X and 10X.
     

    koshkin

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    Excellent. Thanks for confirming my thinking. I was adjusting the CoC to match the zoom setting, and I specified that I was using 0.020 after 3X on the zoom. I also kept thinking that at high zoom setting, I need to further reduce the CoC accordingly, especially in zoom ratios like 6X, 8X and 10X.

    Now, I am really confused. Neither of the scopes you talked about goes down to 3x.

    ILya
     

    ormandj

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    Some people just need to learn to give up.

    I am looking forward to trying a 4.5-28, I was not terribly impressed with the 42x when compared to higher end glass, and am definitely hoping for a more forgiving optic when it comes to parallax setting and adjustment. The turrets on the 42x blew me away, so hopefully locking turrets at least that nice are on the way.
     

    tbeckstrand

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    Hello ILya, please do not apologize; I do not feel picked on in any way. Au contraire< I am always looking to learn more and I appreciate the corrections you provide.


    Now to answer a few of your questions or comments.


    1- The formula for calculating DOF does not include magnification. I play with the CoC value, adjusting it for magnification as I explained. My picking 0.030 was originally from my photography experience, but I have since found out it works for riflescopes as well, at least as a starting value a low magnification. A happy coincidence? Perhaps. But the CoC range I use is proper.


    2- DOF is definitely dependent of focal length and F-number. I mention that several times in my earlier post, in different ways. I even take the time to discuss the use of the modifier disk that March includes with many of their riflescopes with 52 and 56mm objectives. The reducing on the aperture is equivalent to one full stop, boosting the DOF greatly.


    3- In the other thread where I first discussed the possibility of calculating the DOF of various scopes, I spent quite a bit of time explaining that in order to even attempt that, one needs to have the focal length of the objective lens group. I also stated that no riflescope manufacturer provides that information and that most (probably all) consider it company-proprietary information. This is when I explained how I was figuring it out and that it could only be used as approximation, a guide, if you will. This is the reason I used scare quotes in my post when I said I “measured” the focal length of the two scopes. I would never reveal proprietary information.


    However, all that said, I take your comments about how trying to even measure that without opening a scope, is pretty much a waste of time as different scope probably have different placements for the FFP, certainly across brands and makers. That was why I was talking about a standard way to measure it for all scopes, but now I think that would just be misleading and create confusion.
    I saw your other thread and meant to comment at the time. I know of two reasons (there are probably more) why you cannot measure or approximate the focal length of a rifle scope by measuring the distance from the objective lens group to the location of the first focal plane. The first is you would need to know the composite focal length of the objective lens group since that lens group consists of several lenses, each with a unique focal length. There is no direct correlation between the physical distance of the objective lens group from the FFP and the objective lens group’s composite focal length. The second issue, as pointed out by Ilya, is the presence of the erector assembly and its effect on magnification, completely obviating crude focal length approximations using the scope’s exterior. Camera lenses have nothing resembling an erector assembly, so using camera lens methodology on rifle scopes is folly.
     

    TwistedOneinSeven

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    Glassaholic

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    That is a great deal for sure, March rarely puts their scopes on "sale", this will probably be the last time in a very long time as they are not in the business of doing so, if I understand correctly it is only because of not being able to attend SHOT and IWA this year so they are passing that savings back to their customers.

    Now if we could encourage TT to do a 10% off for their 10th anniversary next year :D
     

    eelman308

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    After much research, discussion, input from a couple guys here, and several days and nights of mind wrangling.......pulled the trigger on the March. Now the wait begins. :p

    Thanks for everyones thoughts and comments!!
     

    Convex

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    Yashica/Kyocera at one point in time decided to produce 35mm legacy cameras; They resurrected the Contax name, hired the Porche Design Group for input into the design of their cameras, along w/a license from Carl Zeiss to produce Carl Zeiss lenses in Japan.

    Their attitude was, you want "made in Germany", you want lush damping, more metal not less, precision and quality, "well we can do that".

    The Carl Zeiss lenses made under license in Japan were every bit as lushly damped as the German lenses, I know, I've got both. The cameras were stylish/innovative and a pleasure to use. Production of these cameras ended close to 2 decades ago, but my Contax AX still works like a champ.

    So w/Contax-Carl Zeiss you got a system that came close to "made in Germany" quality from an outfit who at the time was hungry, innovative, eager to please, and producing "more" for less money than folks who were producing a similar product regardless of where it came from.

    I just got the March 4.5-28X52 yesterday, and waited until I examined the scope before I posted this because from what I've read, March has changed/improved; so after handling how this optic is put together, and how lushly it's damped/feels as an optical instrument, it confirms for me that March is driving in the "same lane" as Yashica/Contax did, at least in spirit

    Having said this, you may not like the scope, but I'll say for me, I've had the bias in the past to want to buy "Made in Germany" 1st, looking at other gear 2nd (when I could afford it), but w/the feel of this scope, the fact that it's from Japan and not Germany, my gut reaction is "so what".