Posted by Basil Greber on July 14, 2006 at 3:49 PM
Hello everybody
I have, among others, a Nikkor 55-200 DX and a Sigma 75-300 lens. The Sigma's colors seemed a bit odd to me, so I performed a test. Result: Colors are allright (more or less), BUT the Sigma is 2.5 stops darker than the Nikkor! I had to dial in -1.5 stops for the Nikkor and +1 stop for the Sigma to get the same exposure with flash (same aperture, same shutter), and the same result persisted in a no-flash situation. How is this possible? I had the same composition (if you want to call it like this...) for both shots, so I don't think it's a metering issue.
Sounds like either an incompatiblity of the electronics or perhaps a bad contact. Either way, the lens is not properly transmitting the aperture to your camera's computer.
Guy
Posted by Basil Greber on July 14, 2006 at 4:56 PM
Thanks Guy. I'll redo the test with manual metering and all that, then. I must say, however, that I have been able to get good shots with that lens. Sometimes I really wonder if there's any logic behind all this...
Basil
Posted by Basil Greber on July 15, 2006 at 1:15 AM
Re-did some testing. I'd say the difference is not as hughe as I initially thought, maybe 1 stop. But still, it's a bit strange... well, I'll have to live with that.
Basil, as long as you're using your camera's built-in meter it shouldn't matter whether you're metering manually or automatically. If the reading is off at any aperture, then the lens is not properly communicating its maximum aperture. If it's specific to one setting then the lens is not communicating that one aperture properly. Either way - your camera's computer doesn't know the real aperture the lens is at, which causes it to suggest the wrong shutter speed.
Guy
Posted by Basil Greber on July 15, 2006 at 9:44 AM
Hi Guy
Thanks for taking the time to answer. Couldn't it be that somehow the glass is a bit more "turbid" in this lens compared to the Nikkor, or that the aperture blades are a bit "smaller", leaving a bigger "hole" in the Nikkor (I know that sounds silly). The reason for asking is this: I have now test-shot with all my lenses, and it seems that actually the Sigma 500 f/7.2, Sigma 75-300 f/4.5-5.6 (which is read by my camera as 4.8-6.0) and Nikkor 50 f/1.8 all give the same image (more or less) at a fixed aperture/shutter setting, while my "new" DX Nikkors (18-55 and 55-200) give brighter images (actually they tend to overexpose!).
Hard to say without seeing the images. If the Nikon images are consistently over-exposed you may need to have Nikon calibrate your meter. Are you sure the camera is not just exposing "to the right"?
I woul still suspect that it's the Sigmas that are most likely at fault. I know they have had compatibility issues with new Canon bodies so it's possible there's some quirks with the new Nikon bodies as well. After all - Sigma reverse-engineered the electronics available at the time these lenses were introduced and is not privy to any tweaks Nikon may have implemented since.
Guy
Posted by Scott Elliot on July 15, 2006 at 9:54 PM
You don't happen to have a polarizer filter on the Sigma?
Posted by Basil Greber on July 16, 2006 at 2:48 AM
@ Guy: Possible that the Sigmas are not 100% compatible (keep in mind however that the Nikkor 50/1.8 meters like the Sigmas, not like the DX Nikkors! discovering this somehow got me away from thinking that the Sigmas are to blame). I had a Sigma 75-300 that didn't work at all, and am happy that my current one works more or less (quite well actually). I was just wondering whether I'm alone with this or if somebody else also has made this experience. I mean, I can work around it. I bought all those lenses used & for very little money (student here...), so there is a trade-off somewhere.
Just a wild speculation....As I understand it the two new DX lenses (designed with digital in mind) give a brighter image, perhaps as much as one stop.
I WONDER if it could have something to do with the crop factor on your camera. The only logical way I can think of for this is if you were using manual flash, and the "digital" lenses were telling the flash to zoom so that the light was concentrated in the actual field of view, while the old non-digital lenses waste a stop or so of light illuminating full-frame coverage.
If you aren't using manual flash, then I still wonder (just speculation, not any real knowledge) if the crop factor issue somehow has something to do with it. I'm a Canon shooter, so I have the luxury of not being burdened by any real knowledge of Nikon systems!
Posted by Basil Greber on July 16, 2006 at 3:02 AM
Mike - it's the same whether with or without flash (however, I had the impression that the effect was even more pronounced with flash). However - the camera should "know" that its sensor is small, right? I mean, focal length doesn't change for any lens whether it's mounted on digi or not, it's just the FOV that changes, and the camera should compensate for that. I guess so, at least.
Basil--I can speak to how Canon cameras work, but not how Nikon cameras work.
On Canon cameras, up until the latest model of flash, the flash didn't know (and had no way to know) what size sensor was on the camera. So the (Canon) flash got the focal length of the lens from the camera electronically, and flashed so it would illuminate a full-frame sensor or film at that focal length. So if you were shooting a crop-factor camera, a big part of your light was wasted.
On the newest flashes on the current digital cameras (but not on some old digital cameras made before this idea was incorporated into the flash), the flash gets the focal length of the lens AND gets the crop factor of the camera, and narrows down the area of flash illumination accordingly. So you don't waste any light, and have either greater range for your flash in a given situation, or faster recovery time.
Again, the above is with Canon equipment, I have no idea how Nikon does it.
Your original post said "with flash" and I"d keyed in on that. ONly in looking back now do I see that you said "persisted without flash". So it makes my explanation even less likely!
Discussion
11 repliesI have, among others, a Nikkor 55-200 DX and a Sigma 75-300 lens. The Sigma's colors seemed a bit odd to me, so I performed a test. Result: Colors are allright (more or less), BUT the Sigma is 2.5 stops darker than the Nikkor! I had to dial in -1.5 stops for the Nikkor and +1 stop for the Sigma to get the same exposure with flash (same aperture, same shutter), and the same result persisted in a no-flash situation. How is this possible? I had the same composition (if you want to call it like this...) for both shots, so I don't think it's a metering issue.
Any ideas? And any clue how to correct this?
Basil
Guy
Basil
Basil
Guy
Thanks for taking the time to answer. Couldn't it be that somehow the glass is a bit more "turbid" in this lens compared to the Nikkor, or that the aperture blades are a bit "smaller", leaving a bigger "hole" in the Nikkor (I know that sounds silly). The reason for asking is this: I have now test-shot with all my lenses, and it seems that actually the Sigma 500 f/7.2, Sigma 75-300 f/4.5-5.6 (which is read by my camera as 4.8-6.0) and Nikkor 50 f/1.8 all give the same image (more or less) at a fixed aperture/shutter setting, while my "new" DX Nikkors (18-55 and 55-200) give brighter images (actually they tend to overexpose!).
Basil
I woul still suspect that it's the Sigmas that are most likely at fault. I know they have had compatibility issues with new Canon bodies so it's possible there's some quirks with the new Nikon bodies as well. After all - Sigma reverse-engineered the electronics available at the time these lenses were introduced and is not privy to any tweaks Nikon may have implemented since.
Guy
@ Scott: No.
Basil
I WONDER if it could have something to do with the crop factor on your camera. The only logical way I can think of for this is if you were using manual flash, and the "digital" lenses were telling the flash to zoom so that the light was concentrated in the actual field of view, while the old non-digital lenses waste a stop or so of light illuminating full-frame coverage.
If you aren't using manual flash, then I still wonder (just speculation, not any real knowledge) if the crop factor issue somehow has something to do with it. I'm a Canon shooter, so I have the luxury of not being burdened by any real knowledge of Nikon systems!
I'm still wondering...
Basil
On Canon cameras, up until the latest model of flash, the flash didn't know (and had no way to know) what size sensor was on the camera. So the (Canon) flash got the focal length of the lens from the camera electronically, and flashed so it would illuminate a full-frame sensor or film at that focal length. So if you were shooting a crop-factor camera, a big part of your light was wasted.
On the newest flashes on the current digital cameras (but not on some old digital cameras made before this idea was incorporated into the flash), the flash gets the focal length of the lens AND gets the crop factor of the camera, and narrows down the area of flash illumination accordingly. So you don't waste any light, and have either greater range for your flash in a given situation, or faster recovery time.
Again, the above is with Canon equipment, I have no idea how Nikon does it.
Your original post said "with flash" and I"d keyed in on that. ONly in looking back now do I see that you said "persisted without flash". So it makes my explanation even less likely!