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 Replies: 10 / Views: 3,063 |
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Valued Member
United States
71 Posts |
I recently bought a fixed aperture 75ARD1. While I am very impressed with the sharpness of the lens at 1x, the chromatic aberration of the lens seems to be pretty obvious. I checked Mark Goodman's site, and his comments are "This lens shows minimal color fringing on the periphery at 1:1, and mild to moderate color fringing at magnifications above and below 1:1." I am uploading some pictures taken at 1:1 to show the chromatic aberration of the lens.    In comparison, el Nikkor 75mm does not show visible CA:  Did I receive a bad specimen, or is this amount of CA normal for this lens? |
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Pillar of the Community
2087 Posts |
I cant see any CA in the second photograph( could be the color setting of my monitor). One possibility is that the lens has had the coatings damaged or removed through cleaning. I have found that sometimes on ebay some people buy fungus hit objectives Clean them and the sell them without noting that the fungus( and coatings) have been removed. |
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Pillar of the Community
United States
5825 Posts |
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Pillar of the Community
United States
9395 Posts |
When I first saw these on my tablet, I didn't seen anything either. On my regular LCD monitor, it's readily visible.
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Valued Member
 United States
71 Posts |
Quote:
When I first saw these on my tablet, I didn't seen anything either. On my regular LCD monitor, it's readily visible. Right. It is not obvious on my notebook screen either, but on my external monitor, purple fringing is easy to see. |
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Valued Member
United States
71 Posts |
Quote:One possibility is that the lens has had the coatings damaged or removed through cleaning. I have found that sometimes on ebay some people buy fungus hit objectives Clean them and the sell them without noting that the fungus( and coatings) have been removed. Thanks for feedback. The seller did say it was "refurbished", without giving any details. |
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Pillar of the Community
Canada
2784 Posts |
i purchased one. the seller that said the same thing. the one I have. functions the same as yours. I thought it was just myself. thanks for posting this it helps me as well. payed a lot of money for this lens. well it works good with copper.
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Pillar of the Community
 United States
4038 Posts |
My copies of this lens don't show this behavior. One thing different about the two images above is the exposure. The 75ARD1 image is exposed a stop or two higher. It's these over-exposed areas that are showing the CA, and it may be that it's not so much CA as exposure bleed. I'd suggest dropping the exposure so that the highlights match the 75ELN, and then make the comparison again.
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Valued Member
United States
71 Posts |
I am aware that the pictures taken with 75ARD1 were overexposed. Today I took more pictures, both with 75ARD1 and el Nikkor 75. I reduced exposure for 75ARD1, and increased exposure for the el Nikkor. With faster shutter speeds, the purple fringing is gone for 75ARD1 at 50% crop.  But at 100%, slight fringing can still be detected:  On the other hand, el Nikkor shows no fringing even when the photo below is over-exposed on purpose:  There seems to be some green fringing in the picture below:  It looks that 75ARD1 is a lot more sensitive to over-exposure than el Nikkor 75mm. Edited by coinphotofan
05/16/2016 01:06 am
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Pillar of the Community
United States
4038 Posts |
I find that is true for higher resolution lenses. In general I shoot such that I get an absolute minimum of saturated highlights for this reason.
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Pillar of the Community
United States
9395 Posts |
I went back and looked for CA in pics taken with the 75ARD1/V. Usually, I shoot around f/6.8 (half way between f/5.6 and f/8) and don't see much CA. Magnification is usually 0.9x down to 0.3x or so. I did see quite a bit of CA in one shot of the famous "Panama Pill" 10mm diameter coin, shot at about 1.4x, with the Canon T6s APS-C sensor. I had to do stacking with Zerene Stacker to get everything in focus, so I was able to shoot at f/4 or thereabouts this time. Here is a 100% crop of a 2mm or so square near the center of the coin:  I don't know if the f/4 at 1.4x made the CA visible? Perhaps the stacking exaggerated any CA originally in the shots? (I no longer have the original frames used to make up the stack.) |
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Replies: 10 / Views: 3,063 |
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Posted 05/15/2016 08:41 am
