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08-01-2018, 07:03 AM   #1
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Perhaps a silly question: Is it haze or just overexposure?

Hi,
Yesterday I made a comparison of my old zooms: F35-70,F35-105, F35-135 and A70-210. (Pictures in that order). Same camera, K3II, samemotives, same focal lengths, same multi segment metering, same white balance(or so I thought), P, ISO 400, no compensation. The three firstwith a good hood, 70-210 only the built-in one.
The result worried me. Especially 35-105 and, to alesser extent, 70-210. Are they developing haze? Do I have to say goodbye tofriends who have been with me for 25-30 years. Or do they just overexpose?
Here the first three lenses at 35mm.
No, the 35-105 often hade the same exposure values asthe others, sometimes 2/3 over, sometimes even a bit under. The strange thingis that it sometimes seemed to follow a different program line. In one case theother lenses had 1/400 f8, while 35-105 had 1/40 f22.
But still, the problems diminish substantially, ifthey donít disappear totally, if I underexpose consistently by one stop. Thenof course pix with the other lenses get murkier.
Strangely enough the problems hardly occur with thesame motives, same lenses on my K20D.
So is it developing haze? How can I tell? Anything Ican do?

I should mention that in a different thread last year Iasked whether my K3II did overexpose generally. https://www.pentaxforums.com/forums/172-pentax-k-3/342054-what-went-wrong-my-k3ii.html#post3943835

BTW. At the end of the experiment my camera whenbananas. Suddenly it started firing by itself, and more or less the same pixwere taken again, but often much paler, often vertically, sometimes with doubleexposures. And the white balance went wild. And the camera created a newseparate file folder for every 1-2 pictures. Then I discovered that the camerahad been changed to serial shooting unintentionally. And the white balance hadbeen set to brilliant. But does that explain everything? Is there a way to prevent unintentional changes? The battery was prettylow at the time, and the memory card was running out. And it was very hot bySwedish standards, over 31C/F92 but that isnothing in some other countries.

Any comments welcome

Max
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08-01-2018, 08:20 AM - 1 Like   #2
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Have you inspected the lens elements by shining a flashlight through them? You can usually see haze developing on the inside that way and it has a bit of a fuzzy look to it. If you can't see anything, it's probably not haze. I'd probably inspect the lens you used to take that second picture.
08-01-2018, 09:06 AM - 1 Like   #3
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I believe this is the case where using a proper lens hood would help.
08-01-2018, 09:38 AM   #4
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It looks like a loss of contrast due to stray light to me. Different lenses might show different responses to stray light due to the type of elements, coatings, number of elements, various hoods used (or not used), etc. The same applies to exposure settings, which on digital cameras can vary a fair bit for older lenses. Maybe try metering using live view, which should give you more consistent results.

I'd use the flashlight as WillReaver suggested, and check whether there's haze. I think it there would have to be a lot of haze for it to notably affect the image quality though. If you really have to look for it, then it's probably not an issue.

If you keep getting problems, also check whether there's no loose elements (gently shake lenses) or whether the aperture blades are fast and snappy.

08-01-2018, 12:04 PM   #5
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White saturation is caused by light which is absorbed by the lens. Remove the hood. Flip back and forth AF and MF then back to AF then rotate camera to portrait then shoot using timer if the result is the same. If that happens turn on distraction correction.
08-01-2018, 12:37 PM - 1 Like   #6
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I'm no expert on older lenses but i have a couple that behave similar to what your showing and i believe it is ghosting. Try different angles to the sun and see if the results are the same? I bet they are not.
08-01-2018, 03:43 PM - 1 Like   #7
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Do you have filters on the lenses? Remove them or clean them.
08-01-2018, 07:22 PM   #8
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I think it's an interesting question.

If everything was equal and the scene challenged lens coatings in particular, the F35-70 should be the best. It has only 8 elements. The other lenses have 13 (older coatings), 14 and 16 elements. If your apertures were different, that's a different amount of stray light bouncing around each lens.

Hoods, maybe. It looks more like direct light which the hood doesn't block. You could make a hood out of cardboard which is great for one focal length and use it on all the lenses. They are all 58mm filter size except for the F35-70. That would control the hood variable.

Exactly the same exposure would be better but you'd probably have some brightness mismatch anyway, so it wouldn't be perfect.

08-02-2018, 07:05 AM   #9
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Original Poster
Thanks a lot for useful comments,everybody.
Sorry about my Spelling. All my spaces disappeared when I copied from Word.
I had done the flash light test, and I have done it again more carefully this time. It does not look good on the worst lenses, but it's hard to say if it is dust or beginning fungus.
Yes, all but the 70-210 had hefty hoods, in particularly the main suspect 35-105. The cardboard idea seems interesting but can harldy be used on all focal lengs. Yes, all filters had been removed. The stray light theory is interesting. But the worst case was 35-105 with 14 elements, then 70-210 with 13, 35-70 with 8. and best 35-135 with 16. I din't quite understand penview52's comment on distraction correction.
Thanks again
Max
08-03-2018, 05:25 AM   #10
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" comment on distraction correction "

If the photo is blurry turn off the the distortion if it was turn on. ( Menu - camera icon2 - lens correction, distortion correction set to off )
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