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03-22-2011, 10:51 AM   #1
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Analogue telephoto lenses on digital pentax

I have for 35 years used pentax cameraes including long lenses for nature photography. In the end I also bought Pentax 645 and 600 mm 5,6 ED plus 400mm f4 ED, with great results.
However using the 400 mm f 4 ED on my digital pentax 10D gives some strange effects, especially when shooting e.g. birds flying against a bright skye - som kind of flare I never have with the same lense on old cameraes. But the 400mm FA 5,6 for the K-series works excellently.

Does anyone have an explanation or an idea for solving the problem? I read that other users have good resultas using the 400 mm fED on D20.

03-22-2011, 11:19 AM   #2
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Can you post a sample image as well as a shot of your adaptor. A while back someone had similar issues and it was found to be the bright shinny bits on the mount adaptor. Do a search and you will find the post. You can paint the offending parts flat black to solve the problem
03-22-2011, 02:16 PM   #3
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Makes sense - the two main reasons you see "digital" lenses marketed now:
1) Digital sensors are more reflective than film, which requires higher grade lens coatings. Many old coatings met the grade, but cheaper ones did not. "digital" here just means "higher minimum standards for coating quality". Pentax SMC is more than sufficient to meet and exceed the lens coating requirements for operation on digital cameras. (This is basically what Sigma's "DG" full-frame coverage line is, and Pentax D-FA lenses)
2) One can make wide-angle lenses with reduced image circle coverage and they'll still work. (Sigma DC lenses, Pentax DA lenses)

Now in the case of Pentax MF glass on a mount adapter - these are in category 1, however as mentioned above, the mount adapter could be so shiny that even the best coatings aren't good enough to work with it unless it's de-shined.
03-22-2011, 04:07 PM   #4
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Just a note here but the reason I suggest the mount is out of 30 lenses I have only one with a reflection problem and that is due to shiny parts not sensor / lens reflections

03-23-2011, 01:43 AM   #5
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Analogue lenses digital sensor

Thanks everybody for informative replies.. Actually my adapter 6x7 to 35mm is the original Pentax and black trough out. However my big front filter for protection is probably only single coated since it does not tell anything about it, though otherwise a fine German brand (B&W). But even so - that should not be such a big problem, having such a good built in lens hood.
I might take new analogue shots to be sure nothing has happened to the lens itself - but as I wrote the effect is obviously som king of flare or ghost light destroying the image contrast in otherwise sharp shots, so you might be right after all.
03-23-2011, 01:48 AM   #6
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The only advice I can give is this -- never shoot with filters unless you are after specific effects. I have seen many examples where filters did more harm than good. Only without filters you'll be able to say something about the optical qualities of a lens.
03-23-2011, 06:17 AM   #7
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QuoteOriginally posted by Asahiflex Quote
The only advice I can give is this -- never shoot with filters unless you are after specific effects. I have seen many examples where filters did more harm than good. Only without filters you'll be able to say something about the optical qualities of a lens.
I read an article elsewhere on the net about a Tamron AF 300/2.8 where the person doing the tests got higher MTF figures and better contrast by adding a modern high end UV filter to the front of that lens.

The people in that forum suggested that maybe the somewhat older Tamron coatings don't block as much UV as our current coatings, and were causing the lens to "flare" with UV.

Rubbish? I don't know, but the mtf pictures were entirely convincing.
03-24-2011, 08:32 AM   #8
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Thanks a lot. With other lenses filters never harmed much - but in this case I will really give it a try - my thick 128mm filter probably only single coated could together with some shining things do the harm you talk about. On my 600mm 5,6 (645) which I mostly use on my 10D, tle original huge Pentax protection lens gives no problems, obviously having the best possible coating.
My next wish would be the new 16 mp Pentax with no quality reduction in very high ISO, which means my small 400 5,6 FA will almost always do the job - except for physical exercise of course...In that case the big lens will be used on 645 analogue exclusively.
-So the next question from a poor man would be: How is the picture quality in terms of sharpness comparing the new 16 mp Pentax D7 with analogue 645 and then with the "unachievable"
new Digital 645?

03-24-2011, 08:42 AM   #9
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The test photos of the lenstip UV-filter test seemed convincing enough as to filter (coatings) making a difference with flare; of course, they were shot in conditions prone to that, but that was the point, I guess .
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