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09-22-2020, 09:43 AM - 1 Like   #1
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Are medium format lenses more prone to flare?

Mentioned this in the post pictures thread and decided it deserves its own place. Shooting Q through K-1 I thought multicoating had mostly eliminated lens flare. Unless shooting directly into the sun. Not so sure with digital medium format. Here is an example taken with the 645Z and HD 645 DFA 35mm lens. Taken underneath a park shelter, this is one of the last photos I would've ever guessed to be plagued by flare. Not sure if the barely lit light or sunlight sneaking under the shelter caused this. Neither appear very bright and I'm surprised Pentax's top coating was so easily defeated.

Do you find flare less well controlled in medium format?

Thanks,
barondla

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09-22-2020, 10:56 AM - 1 Like   #2
maw
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QuoteOriginally posted by barondla Quote
Are medium format lenses more prone to flare?
I don't think the medium format lenses are more prone to flare.

Is the lens hood mounted or not? Very important. It would look more like a glow or a small halo on the lens than real flare.

Check against the light for small spots or foggy or dull areas. Could be an abnormal glow from the lamp, and as you know light spreads in all directions and is difficult to handle.

More than anything else it is you who manage it.

Ciao Mario
09-22-2020, 11:06 AM - 2 Likes   #3
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Did you have a protector / UV filter or any other type of filter on the lens?
09-22-2020, 11:13 AM - 1 Like   #4
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Check the lens for fungus

09-22-2020, 12:05 PM   #5
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QuoteOriginally posted by maw Quote
I don't think the medium format lenses are more prone to flare.

Is the lens hood mounted or not? Very important. It would look more like a glow or a small halo on the lens than real flare.

Check against the light for small spots or foggy or dull areas. Could be an abnormal glow from the lamp, and as you know light spreads in all directions and is difficult to handle.

More than anything else it is you who manage it.

Ciao Mario
Yes, Pentax supplied hood was on the lens. No spots or foggy areas on lens elements.

---------- Post added 09-22-20 at 02:06 PM ----------

QuoteOriginally posted by BigMackCam Quote
Did you have a protector / UV filter or any other type of filter on the lens?
No UV or any other filter was mounted on lens.

---------- Post added 09-22-20 at 02:09 PM ----------

QuoteOriginally posted by pschlute Quote
Check the lens for fungus
Thankfully, lens is perfectly clear of fungus or any other problems.

Don't want people to think the flare happens all the time. It's a rare occurrence. Just rarer with other formats. Usually I'd see this before the shot, but the light was dim. Since this was shot on cropped 645 digital camera, the lens hood could be a little longer. Oh well. Not like it's a game changer, or that I'm going to abandon Pentax. Pentax is not doomed!

Thanks,
barondla

Last edited by barondla; 09-22-2020 at 12:20 PM.
09-22-2020, 12:09 PM - 1 Like   #6
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Did you have the viewfinder covered for the exposure?
09-22-2020, 12:10 PM - 1 Like   #7
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QuoteOriginally posted by BigMackCam Quote
Did you have a protector / UV filter or any other type of filter on the lens?
Another interesting observation, now I remember it happened to me photographing a sunset, some halos appeared to me,
however, due to the lights of the streets, more than the sun, so after removing the filter the effect disappeared, to be evaluated.

Ciao Mario
09-22-2020, 12:15 PM - 1 Like   #8
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Hmm... @barondla, do you have more than one photo showing the same effect? If so, is it in a different position each time, or the same? I note from EXIF data that the exposure time for the shot above was 25 seconds, and I'm wondering if this may be sensor related...

09-22-2020, 12:18 PM - 1 Like   #9
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QuoteOriginally posted by barondla Quote
Do you find flare less well controlled in medium format?
barondla
Actually I have less flare issues with my MF lenses but that may be in part because they are all primes. I have a 645 35mm prime and relative to its angle of view equivalent to other formats, the amount of flare is no more or less.

I suspect the cause of the anomaly in your posting is because of a different reason.

Last edited by Alex645; 09-22-2020 at 02:17 PM.
09-22-2020, 12:23 PM - 5 Likes   #10
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The answer is "yes" but it's not a "medium format" lens issue. Instead, it's a general problem with putting any lens made for a larger format camera on any smaller format camera.

In this case, it was a full-size 645 lens on a crop-factor 645 camera. You have a lens designed to cover a 56 mm x 41.5 mm film frame but the sensor is only 44x33. Light from the full-size image is being collected by the lens and entering the camera, mirror box, etc. Light from the extra parts of the scene reflect off surfaces inside the camera and look like flare. But the 645Z viewfinder isn't showing that part of the scene. (If you've removed the petal hood of the 35mm, things wold be even worse!)

Looking at that shot, it seems extremely likely that full outdoor lighting was visible to the lens just below the furthest rafters.

TL;DNR: A lens for a larger format sitting on a camera for a smaller format pulls in a lot of light from parts of the scene that are not visible in the smaller format camera.

The solutions are: 1) adding a smaller petal hood optimized for the smaller format; 2) using only lenses optimized for the format; 3) paying attention to bright elements that lurk just outside the viewfinder but that are visible to the lens.
09-22-2020, 12:54 PM - 1 Like   #11
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Hi photomptimist,

I have no reason not to believe you, but then your speech should also be valid for targets for the native 24x36 format, usually called 'full frame'

and mounted on an aps-c or cropped, is that right?

Ciao Mario
09-22-2020, 01:46 PM   #12
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QuoteOriginally posted by BigMackCam Quote
Hmm... @barondla, do you have more than one photo showing the same effect? If so, is it in a different position each time, or the same? I note from EXIF data that the exposure time for the shot above was 25 seconds, and I'm wondering if this may be sensor related...
Yes, took two shots from the same tripod position taken seconds apart. Both put the flare in the same spot. It was a long exposure in dim light, which is why I was surprised by flare.

---------- Post added 09-22-20 at 03:58 PM ----------

QuoteOriginally posted by photoptimist Quote
The answer is "yes" but it's not a "medium format" lens issue. Instead, it's a general problem with putting any lens made for a larger format camera on any smaller format camera.

In this case, it was a full-size 645 lens on a crop-factor 645 camera. You have a lens designed to cover a 56 mm x 41.5 mm film frame but the sensor is only 44x33. Light from the full-size image is being collected by the lens and entering the camera, mirror box, etc. Light from the extra parts of the scene reflect off surfaces inside the camera and look like flare. But the 645Z viewfinder isn't showing that part of the scene. (If you've removed the petal hood of the 35mm, things wold be even worse!)

Looking at that shot, it seems extremely likely that full outdoor lighting was visible to the lens just below the furthest rafters.

TL;DNR: A lens for a larger format sitting on a camera for a smaller format pulls in a lot of light from parts of the scene that are not visible in the smaller format camera.

The solutions are: 1) adding a smaller petal hood optimized for the smaller format; 2) using only lenses optimized for the format; 3) paying attention to bright elements that lurk just outside the viewfinder but that are visible to the lens.
Makes perfect sense. The sun was close to or had already set. The lens hood doesn't provide perfect coverage due to the crop sensor. In this case liveview would be only a little more helpful, due to its slightly wider view vs the optical viewfinder. Wow, a "simple" photo became a lot more complex.

Don't suppose Pentax makes "crop" lenshoods for this situation? Ran into the reverse with the Pentax Q system, which went from smaller to larger sensor. Thanks for the detailed explanation Photoptimist. Once again you have the answer.

Thanks everyone,
barondla
09-22-2020, 02:14 PM - 1 Like   #13
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Long exposures sometimes are marred by a sort of flare. I took 30 sec exposure pictures inside a Basilica and the interior lights created strange patterns ressembling flare. Maybe the sensor misinterprets those incident lightrays and renders them as flare or ghosts. Try to up your ISO and take shorter exposure pictures to check.

Regards
09-22-2020, 04:33 PM - 1 Like   #14
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Funnily enough, I do find exposure length seems to be a factor. When shooting my urban star trail images (in bright places), I usually do a long exposure on ISO 100 (and a narrow aperture) to layer onto the star trail files. I fairly often find flaring on those files in the sky (if there is a street light or similar just out of frame); however, shorter exposures taken on a higher ISO (and a wider aperture) are much less likely to show that flare to a noticeable degree, with the camera in precisely the same position. Of course, I have changed several variables at once (exposure duration; ISO; aperture) and any of these (or a combination of them ) could be responsible. However, it isn't to do with the overall lightness of the file, because I ensure that the exposure adjustments make the files match each other in brightness. I can't say I am sure which variable(s) is/are causing this, but it happens often enough to be a clear trend. I tend not to worry about it, because those low ISO files are not there to be used in the sky areas (and that's where the flare tends to show up noticeably in these shots) - but I offer it to you as a fact that might be helpful. It says nothing about the differing propensity of different image formats (medium format versus smaller formats) to produce flare - but it might at least explain why your 25 second file was so prone to it.

Hope this helps,
Ed
09-22-2020, 05:25 PM - 2 Likes   #15
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QuoteOriginally posted by maw Quote
Hi photomptimist,

I have no reason not to believe you, but then your speech should also be valid for targets for the native 24x36 format, usually called 'full frame'

and mounted on an aps-c or cropped, is that right?

Ciao Mario
You are correct.

A "full-frame" lens on an APS-C camera will bring in spurious light from outside the APS-C field-of-view and may cause flare, ghosting, or contrast loss. For APS-C cameras, DA lenses probably have better real-world flare properties than "full-frames" lenses although I really hate to to say this is a rule because some full-frame lenses with great coatings might beat a cheap DA lens.

The general problem is that all light gathered by the lens (with its full image circle and intended format size) end up inside the camera. Although a camera mirror box may have "black" walls, limitations in materials mean that even "black" surfaces reflect a fraction of the light that hits them. That reflection then hits the sensor and creates ghosting. The worst-cases of this happen when the sun or other really bright object or area is just outside the frame so it's not visible in the viewfinder but it is visible to the lens.

Last edited by photoptimist; 09-22-2020 at 06:50 PM.
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