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Testing For Apochromatic Correction

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Author Previous TopicReplies: 2 / Views: 1,375Next Topic  
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 Posted 05/03/2016  4:37 pm Show Profile   Bookmark this topic Add austrokiwi to your friends list Get a Link to this Message Number of Subscribers
this post is really to check I have got the technique right and that I am interpreting the results correctly. Why test for APO in the first place? Ans: I have two reasons: the 1st comes from bad experience Some years back I purchased an FD 200mm F4 macro it was a brilliant lens in the field but when it came to coins I would get Chromatic aberration right in the center of many of the coins I was focusing on. I ended up selling the lens 2nd reason I want to improve my skills.

I noticed Mark Goodman on his coin imaging web site that in his lens tests he was using a ruler at 45 degrees and was testing for CA that way.

I have a DOF field calculator consisting of a microscope calibration slide backed by white tape mounted at 45 degrees. With the AGFA 80mm process lens I used that to test for CA. The problem was I really wasn't sure what I was seeing with the results. RMPSRMPS has since confirmed to me it was showing good results meaning very little longitudinal CA. He also mentioned the OLy 80mm Bellows lens was known for poor Longitudinal CA.

So I go the DOF calculator out and took a shot with the Oly 80mm:


Testing-For-Apochromatic-Correction

I was focusing on the 24mm line the 23mm line is high and the 25 mm line was low. Now I can see how the test works around the 23mm line( its out of focus) the red is being focused while at the 25 mm line its green. Now that I can see how a "bad" lens performs its obvious.

By comparison the printing Nikkor 105mm ( an APO lens) produces this:


Testing-For-Apochromatic-Correction

The lack of Chromatic aberration is obvious( now)

And then the Schneider Kreuznach APO 45/4 HM (I was focusing on the 21mm line in this shot.


Testing-For-Apochromatic-Correction

EDIT: as suggested by Ray the AGFA 80mm F4

Its not a true APO ( Compare the shot with that of the printing nikkor which is a true APO), its certainly much better than the Olympus and appears to behind the SK45mm which is sold as being APO. Note there are artifacts of Moire( diagonal lines) some of the pictures.



Testing-For-Apochromatic-Correction

I just discovered that last night I had purchased a Schneider Kreuznach APO 40 F2.8 HM lens. When ever that arrives I will add to this thread.As I said in another thread there is a risk with coin collectors discovering coin photography. I will be selling the SK 45mm if the 40 is as good as it is supposed to be
Edited by austrokiwi
05/04/2016 01:16 am
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 Posted 05/03/2016  8:09 pm  Show Profile   Bookmark this reply Add rmpsrpms to your friends list Get a Link to this Reply
How about the AGFA 80/4 in the same setup/technique?
Contact me for photographic equipment or visit my home page at:
http://macrocoins.com
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 Posted 05/04/2016  07:40 am  Show Profile   Bookmark this reply Add austrokiwi to your friends list Get a Link to this Reply
Continuing my playing:
Minolta 75mm F4.5 ( a truly horrible lens in my experience but you can buy one for under US$10.00)


Testing-For-Apochromatic-Correction

Olympus I'm Zuiko 135mm F 4.5

I like it but as can be seen it isn't that good with CA better than the Minolta 75mm though)



Testing-For-Apochromatic-Correction

Now this next one really shows that little US$75-US$110 80mm AGFA is a good buy. Sony Fe90mm F2.8. It has an ed element a super ed element and costs US$1100.00 and the Agfa( scroll to the bottom of the first post), as CA goes, is competing well with the sony. Both the FE 90mm and the Agfa out resolve the SonyA7rII sensor:



Testing-For-Apochromatic-Correction

Switching cameras: OMD-EM10II with 60mm F 2.8 macro ignore the resolution this was a quick shot at low magnification.... the CA is what I was testing and this modern lens appear to be doing well:





Testing-For-Apochromatic-Correction

And the 4/3rds lens Olympus ED 50mm F2 (its only a 1:2 lens but it has good performance as far as CA goes.



Testing-For-Apochromatic-Correction
Edited by austrokiwi
05/04/2016 2:09 pm
  Previous TopicReplies: 2 / Views: 1,375Next Topic  

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