p.1 #2 · Why does one lens expose a scene darker than another?
Lots of lenses have varying levels of Transmission. Sony lenses have the highest transmission ratios out there, making them the brightest lenses out there at their f/#. Shoot, the 55/1.8 is a t/1.8, something that I thought impossible. It is as bright as the Otis.
I am not saying it is a difference in transmission, but it is the easy answer. You can look those numbers up on dxomark.
p.1 #3 · Why does one lens expose a scene darker than another?
As TheEmrys said, differences in optical transmission (most likely) or possibly variation in the aperture. Not all lenses have well calibrated apertures, but variations in light transmission may be most common.
p.1 #4 · Why does one lens expose a scene darker than another?
I just did a comparison with those lenses. Shooting an evenly illuminated grayish wall in manual at f/8 using Spot L, the CV frame is brighter. Shooting in aperture priority, the camera chose 1/25 for the Batis and 1/30 for the CV. The difference between the manual shots is more pronounced than the ones in aperture priority. I'll have to compare Spot with Evaluative at some point soon.
p.1 #5 · Why does one lens expose a scene darker than another?
I could understand transmission being a factor in shutter speed... a lens that transmits more light is going to need a faster shutter speed to avoid over exposure. But that doesn’t explain why the image is actually darker. Why is the meter not exposing the images the same? It has to be something related to how a scene is metered with an adapted lens vs native or something related like that. Otherwise my meter is whacked.
p.1 #6 · Why does one lens expose a scene darker than another?
virtualrain wrote:
I could understand transmission being a factor in shutter speed... a lens that transmits more light is going to need a faster shutter speed to avoid over exposure. But that doesn’t explain why the image is actually darker. Why is the meter not exposing the images the same? It has to be something related to how a scene is metered with an adapted lens vs native or something related like that. Otherwise my meter is whacked.
With native lenses, and depending on the particular camera settings, you may be in the situation where the metering is done wide open then aperture closes when the shot is actually taken, and the camera applies a correction factor. With adapted lenses you always meter at working aperture.
p.1 #7 · Why does one lens expose a scene darker than another?
d.s. wrote:
I just did a comparison with those lenses. Shooting an evenly illuminated grayish wall in manual at f/8 using Spot L, the CV frame is brighter. Shooting in aperture priority, the camera chose 1/25 for the Batis and 1/30 for the CV. The difference between the manual shots is more pronounced than the ones in aperture priority. I'll have to compare Spot with Evaluative at some point soon.
Sorry, but what images are brighter or darker and under what conditions? In one test you say the CV is brighter, but you only comment on the shutter speed in the second test... not the brightness of the image.
I consistently found that the CV images were under exposed and that the meter was selecting a faster shutter. And since a faster shutter should mean less light, the sensor is performing as expected. What doesn’t make sense is why the meter thinks it needs a faster shutter with the CV even though the image is clearly dimmer in the EVF. What could possibly be affecting the meter - fooling it into thinking the image is brighter than it actually is?!
p.1 #8 · Why does one lens expose a scene darker than another?
vdo1 wrote:
With native lenses, and depending on the particular camera settings, you may be in the situation where the metering is done wide open then aperture closes when the shot is actually taken, and the camera applies a correction factor. With adapted lenses you always meter at working aperture.
Hmmm that’s interesting. I wonder if there’s something to this. If true, it’s algorithm is pretty poor. Having a stop difference in some cases is bizarre.
p.1 #9 · Why does one lens expose a scene darker than another?
virtualrain wrote:
Hmmm that’s interesting. I wonder if there’s something to this. If true, it’s algorithm is pretty poor. Having a stop difference in some cases is bizarre.
Set it to AF-C and Live Preview on, then it will pretty surely meter at working aperture.
For the opposite, try AF-S and Live Preview off. Some lenses will meter and do the AF wide open or at f/2.
p.1 #13 · Why does one lens expose a scene darker than another?
Definitely it has to do with your metering mode. It also has to do with if the metering system needs any additional info from the lens. I used to adapt lenses and I say that adapted lenses give more inconsistent exposure than native.
p.1 #14 · Why does one lens expose a scene darker than another?
I find this specially in adapted lenses, and even more if the vignetting of the lens is severe. The camera can't calculate how much of the vignetting is clearing when stepping down, and in return stepped down pictures can be overexposed when metering the whole frame. Try center metering, or just knowing your lens, dial back -2/3 eV compensation or so when shooting small apertures, etc.
p.1 #15 · Why does one lens expose a scene darker than another?
I don't know that adapter so I should probably keep quiet, but assuming there are no known issues with it, I am going to ask some really dumb things. Excuse me for even asking as I know you are better than this, but I have done worse myself!
Did you consider it is 75 vs. 85 so not the same scene? Consistently and 0.3 -1.0 do not really obviously go together: it is a range covering both "Who cares?" and "What the.....?!?".
Did you check the aperture reported against the aperture set on the CV 75?.
One more, but not dumb: Is e-front-curtain shutter off. I heard of problems with adapted A-mount lenses because they could literally not move fast enough with the e-front-curtain shutter, resulting in variable underexposure.
If the Batis (and your other lenses) are not problematic, and it is not one of the above (mine or others) then it may well be that incorrect information is being reported - as already suggested. I had a CV 40 that regularly told the camera it was at f/1.2, which was a real issue at f/8. That was a problem with electronics. Although not likely anything like your problem (mine was not an adapted lens for a start) it made me more aware of the communication going on and that it could go wrong. Do you have other lenses to try on the adapter?
p.1 #16 · Why does one lens expose a scene darker than another?
numbertwo wrote:
I find this specially in adapted lenses, and even more if the vignetting of the lens is severe. The camera can't calculate how much of the vignetting is clearing when stepping down, and in return stepped down pictures can be overexposed when metering the whole frame. Try center metering, or just knowing your lens, dial back -2/3 eV compensation or so when shooting small apertures, etc.
Interesting. Two things... (1) it sounds like your adapted photos are over exposed? Mine are under exposed. (2) I guess I don’t know why the camera doesn’t meter the scene based simply on the readout from the sensor. It shouldn’t need to calculate anything... nothing is changing... with a manual adapted lens, what it sees is what it gets... and what it’s seeing is being underexposed and it doesn’t seem to care. It’s very strange to me.
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PaulMaewpa2 wrote:
I don't know that adapter so I should probably keep quiet, but assuming there are no known issues with it, I am going to ask some really dumb things. Excuse me for even asking as I know you are better than this, but I have done worse myself!
Did you consider it is 75 vs. 85 so not the same scene? Consistently and 0.3 -1.0 do not really obviously go together: it is a range covering both "Who cares?" and "What the.....?!?".
Did you check the aperture reported against the aperture set on the CV 75?.
One more, but not dumb: Is e-front-curtain shutter off. I heard of problems with adapted A-mount lenses because they could literally not move fast enough with the e-front-curtain shutter, resulting in variable underexposure.
If the Batis (and your other lenses) are not problematic, and it is not one of the above (mine or others) then it may well be that incorrect information is being reported - as already suggested. I had a CV 40 that regularly told the camera it was at f/1.2, which was a real issue at f/8. That was a problem with electronics. Although not likely anything like your problem (mine was not an adapted lens for a start) it made me more aware of the communication going on and that it could go wrong. Do you have other lenses to try on the adapter? ...Show more →
Good questions.
- The adapter is a dumb metal ring that adapts L39 screw mount to E-Mount
- I would expect the scene from the wider 75 to gather a bit more light than the 85, but I would still expect the image to be properly exposed from both lenses. Not the 75 consistently underexposed compared to the 85.
- EFC is off for the adapted lens. It is on for the Batis. I have M3 on the mode dial setup for Aperture priority, manual focus and no EFC. The Batis was being shot with the Mode Dial on A which is set for AF-S and EFC enabled.
- I do not have another adapted lens, but perhaps taping over the contacts on the Batis will tell me something.
I will do more testing this weekend to see if I can find any correlations here.
Unfortunately it seems that we don’t really understand how the metering in the A7RIII works. My obviously false assumption was that if you have no electrical connection with the lens, the meter would just evaluate the scene exactly as it sees it. But for some strange reason, it’s adding exposure for some members, and lowering exposure for me. It makes no sense, but I’m sure that’s because, at least so far, we don’t know how the metering actually works.
p.1 #17 · Why does one lens expose a scene darker than another?
virtualrain wrote:
Interesting. Two things... (1) it sounds like your adapted photos are over exposed? Mine are under exposed. (2) I guess I don’t know why the camera doesn’t meter the scene based simply on the readout from the sensor. It shouldn’t need to calculate anything... nothing is changing... with a manual adapted lens, what it sees is what it gets... and what it’s seeing is being underexposed and it doesn’t seem to care. It’s very strange to me.
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Good questions.
- The adapter is a dumb metal ring that adapts L39 screw mount to E-Mount
- I would expect the scene from the wider 75 to gather a bit more light than the 85, but I would still expect the image to be properly exposed from both lenses. Not the 75 consistently underexposed compared to the 85.
- EFC is off for the adapted lens. It is on for the Batis. I have M3 on the mode dial setup for Aperture priority, manual focus and no EFC. The Batis was being shot with the Mode Dial on A which is set for AF-S and EFC enabled.
- I do not have another adapted lens, but perhaps taping over the contacts on the Batis will tell me something.
I will do more testing this weekend to see if I can find any correlations here.
Unfortunately it seems that we don’t really understand how the metering in the A7RIII works. My obviously false assumption was that if you have no electrical connection with the lens, the meter would just evaluate the scene exactly as it sees it. But for some strange reason, it’s adding exposure for some members, and lowering exposure for me. It makes no sense, but I’m sure that’s because, at least so far, we don’t know how the metering actually works. ...Show more →
Ah ok, you're using a manual lens so the aperture is manual and you're focusing and shooting at the final aperture, so yes, it's weird that the images are underexposed, because the camera is exposing what the sensor "sees", so I don't know what happens. My issue is with some adapted AF lenses, because the camera meters wide open, and when stepping down, it might be less than a full stop in the center and the final picture is a bit overexposed...
