5D4 exposure variance ..... can anyone explain this?

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If I take a burst at 6FPS of the same scene, with constant light, and the same settings, then the exposure (brightness) of two successive images within that burst should be the same, right? I mean each frame was taken with the same shutter speed, the same ISO, and the same aperture. In the same light.

Given that, why do these two images vary so much? . Why is one brighter than the other? . I would guesstimate that the top image is 1/2 of a stop brighter than the bottom image.

I have had this happen a lot with my 1D Mark 4, and the differences between light and dark images was much more extreme (like 3 or 4 stops apart). . I just figured the 1D4 was on its last legs, and that something inside it was screwed up. . But now this is happening with the 5D4 that I just got 8 months ago, and it is starting to concern me.

If anyone can shed some light on this, I would be interested in hearing it.

EXIF (both images): Canon 5D4, Sigma 300-800mm f5.6 @ 800mm, 1250 ISO, f9, 1/800th of a second

This is a really wild guess. In looking at the two photos, the darker one seems to have a greater depth of field than the lighter one. If that's true, the iris in your Sigma lens might be closing further than it should. That would have the effect of a higher f/stop (less light and larger DOF).

You have Auto Lighting Optimizer and Highlight Tone Priority Off, yes?

Snydremark wrote in post #19111249
You have Auto Lighting Optimizer and Highlight Tone Priority Off, yes?

I don't know about the new "enhanced" HTP, but I have never found the classic one to put middle grey at a greater level of interpretation, and is pretty deterministic. It just rolls down highlights in a deterministic way with lower-contrast picture styles, and does nothing for high-contrast ones, except have more hidden RAW headroom.

It's easy enough to examine Tom's RAW files in RAWDigger. If the masked pixels have the same sigma, then the actual combined analog and mathematical gains are the same, and then if there is any difference in RAW histograms or rendered brightness, then the RAW data was treated differently because of metadata in Tom's conversions. If the masked pixels are scaled differently, then the firmware did something different.

I suspect aperture inconsistency, though, as another poster suggested. Tom may need a new aperture motor. That happened to my 100-400L several years ago.

That, or a plane flew over, or trees moved in the wind and made a change in lighting. Outdoor daylight is not always stable. The relative histograms vs sigmas in RAWDigger should determine if exposure was actually the same.

LJ3Jim wrote in post #19111225
This is a really wild guess. In looking at the two photos, the darker one seems to have a greater depth of field than the lighter one. If that's true, the iris in your Sigma lens might be closing further than it should. That would have the effect of a higher f/stop (less light and larger DOF).

Wild guess, I think you nailed it.

What does the EXIF data tell you ??

auto iso or any auto settings could throw off shutter speed

start there first

I got rid of my 1DMKIV for this reason alone. I would be shooting formals with everything being fixed and controlled and had the same issue. At receptions when this happened I attributed it to flash use because I shoot ETTL all the time. Really not 100% sure why this would happen. I dont think its your lens. Possibly because YOU WERE ON A BURST and the card didnt keep up ?? the SD slot is crippled on the 5D4 so perhaps its with the burst and cards not being able to keep up


best guess

umphotography wrote in post #19111429
... Possibly because YOU WERE ON A BURST and the card didnt keep up ?? the SD slot is crippled on the 5D4 so perhaps its with the burst and cards not being able to keep up


best guess

It's got to be either at the point of capture or at the point of conversion. Writing the data to the card will not cause exposure variations. Two things would help, access to the full EXIF of each image and access to the raw files.

If the EXIF is identical and the raw files are the same, then the issue would be at the point of raw to JPEG conversion.

If the EXIF is identical and the raw files are different, then I would start looking at lens aperture blades or something affecting the shutter opening. At 1/800th, the shutter is a tiny slit that travels from the top of the sensor to the bottom. In burst mode it may be possible that the shutter slit size is not the same. The Slo-mo guys did a great video showing the shutter in action. Maybe in bust mode it doesn't have time to fully recover and the second exposure has a smaller opening resulting in a darker image.

Snydremark wrote in post #19111249
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You have Auto Lighting Optimizer and Highlight Tone Priority Off, yes?
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I assume so.

When I bought the camera from my friend, he set it back to the factory defaults, and I have not changed anything in the menus except to re-enable back button focusing. . Neither of these things are just things that would go on by themselves, would they?


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umphotography wrote in post #19111429
I got rid of my 1DMKIV for this reason alone. I would be shooting formals with everything being fixed and controlled and had the same issue. At receptions when this happened I attributed it to flash use because I shoot ETTL all the time.

It happens to an extreme degree with my 1D4. . Like one frame will be so dark it just looks completely black in the LCD playback, while the frame right after it would be perfect exposure. . But I never use flash, so it couldn't have been that with my 1D4, as you suspect it is with yours.

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umphotography wrote in post #19111429
Really not 100% sure why this would happen. I don't think it's your lens.

I tend to think it is not my lens, either, because it happens with all of the lenses that I use.

I mean, the odds of all 4 lenses having an aperture motor go bad at the same time are practically impossible, are they not?

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umphotography wrote in post #19111429
Possibly because YOU WERE ON A BURST and the card didnt keep up ?? the SD slot is crippled on the 5D4 so perhaps its with the burst and cards not being able to keep up

I suppose that's a possibility. . But I should note that I don't use SD cards in my 5D4. . I only use one card slot, and that would be the one for the CF card.

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umphotography wrote in post #19111429
best guess

Thank you, Mike!


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The flicker of the sun was captured by some of the frames taken, so enablement of the anti-flicker feature of the camera might address the problem.



but then again, it probably would not fix the problem.

gjl711 wrote in post #19111441
. At 1/800th, the shutter is a tiny slit that travels from the top of the sensor to the bottom. In burst mode it may be possible that the shutter slit size is not the same. The Slo-mo guys did a great video showing the shutter in action. Maybe in bust mode it doesn't have time to fully recover and the second exposure has a smaller opening resulting in a darker image.

Given the fact that the camera in question has some miles on it, I would suspect the shutter mechanism to have some 'play' causing the shutter slit to vary a bit in width, accounting for the variance in captured brightness from shot to shot.

Tom Reichner wrote in post #19111497
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I assume so.

When I bought the camera from my friend, he set it back to the factory defaults, and I have not changed anything in the menus except to re-enable back button focusing. . Neither of these things are just things that would go on by themselves, would they?

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I believe both default to On, IIRC. As other folks mentioned, neither is *likely* to be a culprit/contributor; they're just both "helper" functions that the camera automates for the user that can affect your outcomes without photog inputs. So, wanted to check to eliminate 'hidden' variables

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Thanks for the insights about the shutter.

I have found with my 6D that a shutter isn't either "good" or "non-functioning". . There can be a lot of in-between shutter conditions, where the shutter still "works", but works poorly and/or inconsistently due to partially falling apart, as opposed to just completely going out on you.

I wouldn't be surprised if it is a partially dysfunctional shutter that is causing this inconsistent exposure issue in both my 5D4 and my 1D4.

I am not easy on my camera bodies, and they endure a lot of knocks and bumps, a 3 or 4 foot drop from time to time, getting soaked in rain or melting snow, salt water and sand exposure, a lot of very extreme temperature swings, being slung around in rapid motion when I do intentional camera movement imagery, etc. . All of the bodies I have owned are constantly getting lubricant splattered all over the sensor due to me swinging then around so fast when I do the ICM stuff. . And they have always gotten tons of error messages and refused to shoot until I turn them off, remove the battery, put the battery back in, and turn them on again. . It's all just stuff that cameras seem to do if I am their owner.

It doesn't seem far-fetched to think that the extreme use could cause a shutter to have some issues, in which it doesn't always function exactly as it should.

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gjl711 wrote in post #19111441
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..... Maybe in bust mode it doesn't have time to fully recover and the second exposure has a smaller opening resulting in a darker image.
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I realize that this was just a misspelling, but to me it really does feel like "bust mode", because it seems that something is busted


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