Shot A, Shot B

This happens all the time. I get a shot and take several pics using high continuous. The first shot is correctly exposed, but the second is noticeably more exposed. I have not moved the camera or focus point. The bird has not moved, nor the light shifted. The two below are one second apart and have the same exif data. Is this a result of using continuous auto focus, having the Tam stabilize on, or what? It is so consistent, I often count on it to bracket iffy shadow shots. If I shot a burst of four, I get dark/light/dark/light. Do others see this?

first shot


second shot

I checked both shots in RT and the histogram clearly shows that there is an exposure difference between both shots.

I checked the EXIF but all should be (about) identical. It says auto-ISO enabled but the data shows an identical value for both. Maybe set it to a fixed ISO and then shoot a series to check if the problem is caused by auto-ISO.

I vaguely remember having a similar issue with the D3300 but I can't remember what exactly it was. It was tied to some auto-mode.

Is it specific to the Tammy? I can't say that I noticed the same behavior with my D5300, but then I never tried to match up a Tamron lens to that body either.

J-see said:

I checked both shots in RT and the histogram clearly shows that there is an exposure difference between both shots.

I checked the EXIF but all should be (about) identical. It says auto-ISO enabled but the data shows an identical value for both. Maybe set it to a fixed ISO and then shoot a series to check if the problem is caused by auto-ISO.

I vaguely remember having a similar issue with the D3300 but I can't remember what exactly it was. It was tied to some auto-mode.

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RocketCowboy said:

Is it specific to the Tammy? I can't say that I noticed the same behavior with my D5300, but then I never tried to match up a Tamron lens to that body either.

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Primarily, yes, but I have also seen it on my Tam 16-300, though I do not shoot that enough these days to have it stand out. My other 5300 has my 90 macro, but that is set to single shot and almost always with a flash mounted, so have never seen it. I will switch the bodies and set up at fixed ISO and see what that does.

There definitely is something very odd going on here. The EXIF data for both pictures show identical shutter speed, aperture, and ISO settings, and that they were taken two seconds apart.

The only way that this seems possible, assuming no malfunction or otherwise unexpected and unaccounted behavior on the camera's part, would be for the light level to change significantly in those two seconds—something along the lines of there being a passing cloud that just happened to be blocking the Sun in the first short,and then cleared in the second.

I can't say that I have noticed it either, but that is not my normal shooting method (High Continuous) I do have my setting to Low Continuous, but rarely do a double shot and if I do, it is usually as I am chasing a BIF or something else moving fast and putting it into different lighting situations for each shot. Maybe I will have to play just for grins and giggles to see if I have the same sort of problem. No Tammy lenses though. Ha!

Bob Blaylock said:

There definitely is something very odd going on here. The EXIF data for both pictures show identical shutter speed, aperture, and ISO settings, and that they were taken two seconds apart.

The only way that this seems possible, assuming no malfunction or otherwise unexpected and unaccounted behavior on the camera's part, would be for the light level to change significantly in those two seconds—something along the lines of there being a passing cloud that just happened to be blocking the Sun in the first short,and then cleared in the second.

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In this case (and others) no wind twitching the leaves, no clouds, no moving bird. I took six paired shots of this bird in different poses -- first was right, second was light, consistently.

I don't know what editor you use but it is possible the problem originates there. Do they already differ when you check them on the LCD?

J-see said:

I don't know what editor you use but it is possible the problem originates there. Do they already differ when you check them on the LCD?

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Yes, very obviously.

Answer with a question,does the EXIF record the aperture used or the aperture the camera says its going to use,if its the second then it could be the lens aperture not closing down properly,could you run a few days on CL to see if it makes any difference.

mikew said:

Answer with a question,does the EXIF record the aperture used or the aperture the camera says its going to use,if its the second then it could be the lens aperture not closing down properly,could you run a few days on CL to see if it makes any difference.

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Good question, with an obvious answer, and perhaps a clue to the problem.

The body controls the lens' aperture by way of a mechanical linkage. The body decides what aperture it means to set, and moves that linkage accordingly. I very much doubt if there is any way for the body to know that the lens actually stops down correctly to the aperture that it means to set, so the aperture recorded in the EXIF must be the aperture that the body intended to set.

Now, with that in mind, look at the bokeh of the two pictures. I realized this, as I was writing the previous paragraph, with the pictures not in view at the time, that I had noticed a difference, and I looked back, and sure enough there it is. In the lighter picture, the background is farther out of focus than in the darker picture. I think this indicates that in the lighter picture, the aperture was open wider than in the darker picture. Between the body working the mechanical linkage to tell the lens how far to stop down, and the lens trying to respond to this linkage, it is apparent that in the end, the lens is not always stopping down as far as it is supposed to.

Did I see the OP, @wev, mention having two D5300 bodies? If so, try the same lens on the other body, and see if you get the same behavior. This will help nail down whether the problem is with the body or with the lens.

Also, it may be helpful, just with the lens itself, not mounted to a body, to work that linkage by hand, and verify whether the aperture is working smoothly and consistently in response thereto.

There's indeed a difference in focus while the EXIF indicates all values were identical. Besides aperture, VR can be a factor too. I didn't check if it was enabled but any correction it does during exposure will result into a slightly different shot.

Bob Blaylock said:

Also, it may be helpful, just with the lens itself, not mounted to a body, to work that linkage by hand, and verify whether the aperture is working smoothly and consistently in response thereto.

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These pictures indicate that linkage on one of my ancient non-AI lenses. That linkage has been on nearly all F-mount lenses since the beginning in 1959. Originally, it was just to allow the aperture to remain open while viewing through the viewfinder, and to be closed down to the selected setting when the picture was actually being taken. The AI-S development in 1981 calibrated that linkage to have a consistent, predictable relationship to how far the aperture was stopped down, so that the camera could use it to control the aperture setting on the lens, and that is how all modern Nikon camera bodies control the lens aperture.

@wev, my suggestion was that with the lens not mounted to a camera, and with the aperture ring set to the smallest aperture, if it has an aperture ring, try manipulating that linkage by hand, and see if the aperture responds smoothly and consistently. I'm thinking now that there's a good chance you'll find that the aperture is acting “sticky”, not always closing down quickly, smoothly, or all the way, and that that is what is causing the issue described in the OP.

I have switched bodies and changed setting to match. I will give it a run today and see what happens.

Horrible light today, but I did my normal sort of walk around and shot around 200 frames with the second body, trying to shot as I normally do. It looks like it may prove to be body related, as I could not get a single instance of the problem to occur. I also noticed a real difference between what I would have expected with the old body in a given set-up versus what I got today. The skies are supposed to clear over the weekend, so I will do further testing.

wev said:

Horrible light today, but I did my normal sort of walk around and shot around 200 frames with the second body, trying to shot as I normally do. It looks like it may prove to be body related, as I could not get a single instance of the problem to occur. I also noticed a real difference between what I would have expected with the old body in a given set-up versus what I got today. The skies are supposed to clear over the weekend, so I will do further testing.

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Since it is now apparent that the problem is with the control of the aperture, and we have known instances of it occurring when the aperture was supposed to be at ƒ/9, try to reproduce this issue with the other body in shots where the aperture setting should be ƒ/9. It shouldn't matter if the shutter speed or ISO are different, because I think it is pretty clear that those aren't where the problem was.

Bob Blaylock said:

Since it is now apparent that the problem is with the control of the aperture, and we have known instances of it occurring when the aperture was supposed to be at ƒ/9, try to reproduce this issue with the other body in shots where the aperture setting should be ƒ/9. It shouldn't matter if the shutter speed or ISO are different, because I think it is pretty clear that those aren't where the problem was.

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Everything I shot today was at f/9 with no issues.

I had something similar happen on my old 50 mm. Sticky aperture blades.

It's easier to try and reproduce the issue by shooting a wall inside (or outside). That way you'll have a constant scene and any irregularities will directly jump out.

You can start everything in full manual with fixed settings and each time introduce a new variable until the issue surfaces.

As Bob said, there is a clear difference in bokeh between the two example shots. This is clearly an aperture issue. When shooting bursts, it often amazes me how well a modern DSLR performs. Think of all the functions it performs at a rate of 6 times per second.

Anyway, I hope you sort it out. If it's the camera body, maybe a trip to the service center would clear it up.