Different exposure on different lens but same camera settings

I have a Nikon 24-70mm and Nikon 50mm 1.8 lens; when I shoot with these lenses on the same camera (D800) same settings on the camera for both lenses (e.g. f2.8, shot at 50mm, 1/100th/s, 500 iso) the exposure is vastly different (50mm prime underexposed, 24-70 exposes brighter. Took this to Nikon repair store here and they compared my 50mm to one of their prime 1.4 50mm, and the exposure was the same, so doesn't seem my prime 50mm is damaged... why does it do that? Is that actually normal?

The 50mm shot is clearly underexposed, and that's not normal. I would guess there is something wrong with the camera's aperture control unit, the assembly that includes the aperture control lever and which is responsible for moving it to the correct position when you trip the shutter. It may be that the lever is not moving far enough (whether up or down, I do not know) to hold the faster lens's aperture wide open.

Something to try: Mount the 50mm on the camera, turn the camera around so that the lens is facing you, and look through the lens while there is something bright, like a blank wall or the sky, in the background so that its light goes through the viewfinder and out the lens. (Leave the camera off for this test, or at least do not put it in Live View.) Does the lens's aperture look like it's wide open, or does it look like it's stopped down? It should look wide open.

The 50mm shot is clearly underexposed, and that's not normal. I would guess there is something wrong with the camera's aperture control unit, the assembly that includes the aperture control lever and which is responsible for moving it to the correct position when you trip the shutter. It may be that the lever is not moving far enough (whether up or down, I do not know) to hold the faster lens's aperture wide open.

 

Something to try: Mount the 50mm on the camera, turn the camera around so that the lens is facing you, and look through the lens while there is something bright, like a blank wall or the sky, in the background so that its light goes through the viewfinder and out the lens. (Leave the camera off for this test, or at least do not put it in Live View.) Does the lens's aperture look like it's wide open, or does it look like it's stopped down? It should look wide open.

Many thanks for that. I have two cameras though, and this happens on both my D800 and D600! So couldn't be the camera, right?

Many thanks for that. I have two cameras though, and this happens on both my D800 and D600! So couldn't be the camera, right?

Probably not then! So if it happens on both of your cameras, and also happens with other 50mm lenses on your camera...maybe it's the world that's broken?

Probably not then! So if it happens on both of your cameras, and also happens with other 50mm lenses on your camera...maybe it's the world that's broken?

Well, that we know, right? :)

I'm thinking maybe my 24-70 overexposes?? But I always felt the images look correctly exposed with that lens... the mystery continues...

If it happens on both cameras, it's the lens.

When Nikon compared it to their 1.4, what did they actually do?

How about trying a 3rd lens with your D600? If two of them produce the same result, then the one that produces a different result may have a problem.

Was thinking the same - I only have a 70-200mm which won't work for this exercise, but I can borrow a more suitable one from the place I hire kit from that I don't have. Will do the whole round of experiments on both cameras... Thanks Mary.

If it happens on both cameras, it's the lens.

 

When Nikon compared it to their 1.4, what did they actually do?

Basically the same as what I did in my test shot (images attached) - I had my D800 with me, took a shot of something in their repair room with my 1.8, they then gave me their 1.4, same camera and settings, and same image, and the exposure was the same as my lens... that's the bit I don't understand. And the exposure was fine, btw. whereas in my sample images it's underexposed.

You could do a similar comparisson between your 24-70 and 70-200 lenses but this time at 70mm ..

Does the 24-70 then still result in a brighter exposure ?

You could do a similar comparisson between your 24-70 and 70-200 lenses but this time at 70mm ..

Does the 24-70 then still result in a brighter exposure ?

Thanks, however, it's my prime 50mm that's giving me the underexposure, so using my 70-200mm wouldn't make it a fair comparison. Am going to borrow another 50mm and see how this exposes...

Two pictures aren't enough to draw any conclusion.

I don't have an EXIF viewer on this device. Were the images taken in manual mode? If not, that's what's needed to determine if the issue is with the lens(es) or the camera metering.

I suggest taking a series of shots at all apertures with both lenses, and controlling both aperture and shutter speed manually. The lighting needs to remain constant, obviously.

If the exposure varies from wide-open to stopped down, then it's very likely that the affected lens has a sticky aperture or bent aperture actuator lever. Less likely is that the AI follower on the lens might be damaged or misplaced.

Another thought occurs to me. What was the light source in your 'test' shots? If it was a mains-powered lamp, then the issue might be shutter-speed related. Mains lighting flickers at 100 or 120 Hz, so a fast shutter speed above 1/125th doesn't catch an entire cycle of flicker. Maybe the shutter speed varied between 1/320th @ f/1.8, and 1/125th @ f/2.8?

Whatever. You need to carry out a few more tests.

P.S. Another thought. Your 50mm prime will be 'unit focussing'; meaning the lens extends to focus close. This results in the effective aperture becoming smaller as the lens focusses closer. OTOH, most zooms shorten their focal length as they focus closer, keeping the aperture constant. This might well account for some of the effect.

So you also need to repeat the test with a subject at a long distance - say over 30ft away.

Two pictures aren't enough to draw any conclusion.

 

I don't have an EXIF viewer on this device. Were the images taken in manual mode? If not, that's what's needed to determine if the issue is with the lens(es) or the camera metering.

 

I suggest taking a series of shots at all apertures with both lenses, and controlling both aperture and shutter speed manually. The lighting needs to remain constant, obviously.

 

If the exposure varies from wide-open to stopped down, then it's very likely that the affected lens has a sticky aperture or bent aperture actuator lever. Less likely is that the AI follower on the lens might be damaged or misplaced.

 

Another thought occurs to me. What was the light source in your 'test' shots? If it was a mains-powered lamp, then the issue might be shutter-speed related. Mains lighting flickers at 100 or 120 Hz, so a fast shutter speed above 1/125th doesn't catch an entire cycle of flicker. Maybe the shutter speed varied between 1/320th @ f/1.8, and 1/125th @ f/2.8?

 

Whatever. You need to carry out a few more tests.

 

P.S. Another thought. Your 50mm prime will be 'unit focussing'; meaning the lens extends to focus close. This results in the effective aperture becoming smaller as the lens focusses closer. OTOH, most zooms shorten their focal length as they focus closer, keeping the aperture constant. This might well account for some of the effect.

So you also need to repeat the test with a subject at a long distance - say over 30ft away.

Two pictures aren't enough to draw any conclusion.

 

I don't have an EXIF viewer on this device. Were the images taken in manual mode? If not, that's what's needed to determine if the issue is with the lens(es) or the camera metering.

 

I suggest taking a series of shots at all apertures with both lenses, and controlling both aperture and shutter speed manually. The lighting needs to remain constant, obviously.

 

If the exposure varies from wide-open to stopped down, then it's very likely that the affected lens has a sticky aperture or bent aperture actuator lever. Less likely is that the AI follower on the lens might be damaged or misplaced.

 

Another thought occurs to me. What was the light source in your 'test' shots? If it was a mains-powered lamp, then the issue might be shutter-speed related. Mains lighting flickers at 100 or 120 Hz, so a fast shutter speed above 1/125th doesn't catch an entire cycle of flicker. Maybe the shutter speed varied between 1/320th @ f/1.8, and 1/125th @ f/2.8?

 

Whatever. You need to carry out a few more tests.

 

P.S. Another thought. Your 50mm prime will be 'unit focussing'; meaning the lens extends to focus close. This results in the effective aperture becoming smaller as the lens focusses closer. OTOH, most zooms shorten their focal length as they focus closer, keeping the aperture constant. This might well account for some of the effect.

So you also need to repeat the test with a subject at a long distance - say over 30ft away.

Hi there, thanks for all this advice. Just a quick response to your questions, yes - I shot in manual. The light was constant and was just natural light from the window. I sat my bottom on the same spot, camera same distance to subject with same focal lengths on both lenses, so the variables pretty much didn't change. I think good advice is a series of test shots, especially at different apertures, I will do that as I had not thought of it. Hopefully I can close this thread with some good news that the issue has been discovered. Thank you!

"If the exposure varies from wide-open to stopped down, then it's very likely that the affected lens has a sticky aperture or bent aperture actuator lever."

Since you tried the 50/1.8 stopped down to 2.8 you may have a bent aperture actuator lever. I would try both lenses at full open and stopped down and and two full stops. That would be enough to you give you an idea of when which lens causes over/under exposure.

I had a lens that over exposed when stopped down but not when shot wide open. That lens went back for adjustment and it was the aperture actuator lever that was slightly out of alignment.

Keep in mind that when you do shoot wide open, you will experience vignetting which will give a darker impression. I would assume your 50 will vignette more than your zoom when shot full open.

Thanks, however, it's my prime 50mm that's giving me the underexposure, so using my 70-200mm wouldn't make it a fair comparison. Am going to borrow another 50mm and see how this exposes...

Ok fair enough, just wanted to make sure thatit is not the 24-70 wich is over-exposing . ...

I don't have an EXIF viewer on this device. Were the images taken in manual mode?

Both: Manual, 1/100, 2.8, ISO 500

So you also need to repeat the test with a subject at a long distance - say over 30ft away.

Focus distance was 0.75m and 0.79m for the 50 and 24-70, respectively. The minimum focus distance for the 50mm is 0.45m and for the 24-70 it's 0.38m. The underexposure (somewhat close to 2 stops is too large to account for the effect - for a unit focusing 50mm lens it should be 2 stops at 1:1 magnification,

I agree with the above suggestions to do a series of shots with varying aperture on both lenses and with a focus distance of at least 10ft.

Your camera uses f-stops which are calculated from the ratio of the nominal focal length and the apparent diameter of the aperture as seen from the rear of the lens.

There are a few problems with that. First, the nominal focal length and actual focal length usually vary, sometimes significantly. In addition, the number of elements and the types of glass and coatings causes some light to be absorbed and scattered as it passes through the lens. Also, zoom lenses do not always perfectly coordinate the variable aperture size with the actual focal length setting. This is why cinematic lenses used (and may still) use t-stops (transmission stops) which take all of this into account.

Of course there COULD be something wrong with either of your lenses or, in the circumstances that you are using to test, these and other factors are producing differences.

If I understand your post, you metered the scene, set shutter speed, aperture, and ISO manually, made an exposure, changed lenses and made another exposure. A few questions:

1) Did you use the camera meter to determine your exposure?

2) Which lens did you use to meter and set the manual exposure - the 50mm or the zoom?

3) If you put the camera in one of the automatic modes - say P Mode - does the 50mm expose properly?

If you metered through the zoom and if the 50mm exposes properly in P-Mode, you may be seeing the difference between T-Stop and F-stop.

Took this to Nikon repair store here and they compared my 50mm to one of their prime 1.4 50mm, and the exposure was the same, so doesn't seem my prime 50mm is damaged... why does it do that? Is that actually normal?

If you experienced the exact same issue at the repair shop using their own 50mm f/1.4, and the problem occurs with both your D800 and D600, you have a real mystery on your hands. Every cause I can think of could not possibly duplicate itself across two separate bodies and lenses: it would be extraordinarily odd.

Setting the aperture to 2.8 on the 50mm lens aperture ring instead of using the camera body control wheels might explain it, but I'd be surprised if the repair tech didn't spot that user error immediately.

Most probable cause has already been suggested in earlier replies: the body is not communicating correctly with the aperture mechanism of the 50mm prime lens. This would be more likely if the 24-70 had fully electronic aperture actuation vs the 50mm primes still using the mechanical stop-down lever in the body (problem in mechanical control mode that is bypassed in electronic control mode). That theory is blown into the weeds by the fact you are having this same glitch with two completely different bodies, and two different 50mm primes (your 1.8 and the repair shop 1.4).

Another possibility would only occur if the 50mm prime lenses were both manual focus (not AF). Manual focus Nikkors use a mechanical AI ring around the lens mount for meter coupling, which can result in slightly different readings, also you need to program the lens maximum aperture into the camera menu system when using MF lenses or exposure readings can be way way off. Alternatively, I suppose both your D800 and D600 might need their lens mount electrical contacts cleaned (they can "get through" to your zoom, but have trouble interfacing with the 50mm primes).

The two different bodies/two different 50mm lenses factor is too weird to be coincidence. It may eventually be discovered that some simple but easily-overlooked setting you made on both your bodies interferes with the 50s but is overridden by the zoom. Testing both lenses on a couple other Nikon bodies you don't own might provide a clue. Better yet would be testing them on a non-Nikon body that does not interact with the lenses at all, like a Canon or Sony using a mount adapter. Set both lenses to the same 2.8 aperture, and if the exposures aren't very close on a Canon/Sony, something is amiss in the lenses. The zoom might underexpose a little, but the discrepancy shouldn't be anywhere near two full stops.

might have missed it, but specifically which 50mm 1.8 is this? My EXIF viewer isn't very specific!

AF-S 50mm 1.8G

Setting the aperture to 2.8 on the 50mm lens aperture ring instead of using the camera body control wheels

Both lenses are G lenses - no aperture ring.

Orsetto's post above brought to mind another possibility . . .

It doesn't matter if you are using the processor in the bodies OR moving RAW files off of the body and producing the JPEGs with other software. The algorithm used to process the image may be producing the difference. I can't say for certain but I don't think that any of the explanations provided so far would surprise me at all.

I did a little experiment, which seems to show that this might be a common 'problem', although not quite as pronounced as the OP shows.

I compared the exposure given by my 50mm f/1.4 Ai-s Nikkor prime and my Tamron SP VC 24-70 f/2.8 zoom.

Methodology was to photograph a piece of white card set too close for the lenses to focus on, such that I got a diffuse and uniform neutral grey exposure. The card was lit consistently and the exposure checked with a handheld incident meter. The exposure settings were held constant at 1/125th and f/4 in manual mode. Camera (a D7200) was at 300mm from the card.

The zoom lens was set to 50mm FL and its closest focus, while the prime was varied in focus from infinity to 0.6m.

Below are the densities got at the same shutter and aperture settings. Obviously showing that the true exposure didn't follow the camera/lens settings.

I consider my camera and lenses to be in fully working order and within specification. So I put the difference down to lens focus 'breathing' entirely.

I estimate the exposure difference between lightest and darkest sample to be approaching 1 stop - much greater than the approximate 1/3rd stop that theory would predict for the change in effective aperture of the prime lens. The leftmost sample would seem to indicate an increase in effective aperture with closer focus for the zoom. An effect that will almost certainly vary from one design of zoom to another.

Add in a little unnoticed variation of natural light, and I'm inclined to believe there's no mystery or issue with the OP's equipment at all.

P.S. The labelling on the rightmost sample is misleading. It should read '@ 0.6m focus' not minimum.