Hi everyone,
I encountered the following fundamental photography question that I just can't figure out. There are probably folks in this forum that know the answer.
I am taking a set of 3 bracketed pictures of a static scene with constant lighting. I am using a Canon 1D Mark IV which allows me to change the bracketed exposure settings to non-integer amounts, so I took brackets of this fixed scene at 2.7ev and 2ev separation between images, just to experiment.
When I examined the LOW image of each bracket, I saw that the -2.7ev exposure was darker than the -2ev as expected. The difference was not large, but was noticeable. However, when I looked at the image properties of this file (through either Windows or Photoshop), I found to my surprise that the aperture, shutter time, and ISO were all identical for the two images (aperture: f/22, shutter time: 1/60, ISO:100). On the other hand, when I looked under Windows at Properties->Details -> Exposure bias for these files, it said correctly "-2.7 step" or "-2 step." But none of the physical exposure parameters were changed!
How can the camera produce two differently exposed images of the same scene with the exact same exposure parameters? I thought that the only things the camera could change to modify the "brightness" of a photograph was aperture, shutter time, and ISO. So if all three are the same, why is the final picture coming out at a different exposure?
This is really puzzling me. The only thing that I can think of is that the camera IS taking the exact same image for both cases because the physical parameters are identical. Perhaps the -2.7ev exposure is undergoing some post-process in the camera (kind of like the ISO gain) that is darkening the image to match the photographer's desired intention of -2.7ev. But there is really no new "information" in the -2.7ev that isn't in the -2ev. But that explanation doesn't make a whole lot of sense to me.
Does anyone have any ideas? Thanks in advance.
I encountered the following fundamental photography question that I just can't figure out. There are probably folks in this forum that know the answer.
I am taking a set of 3 bracketed pictures of a static scene with constant lighting. I am using a Canon 1D Mark IV which allows me to change the bracketed exposure settings to non-integer amounts, so I took brackets of this fixed scene at 2.7ev and 2ev separation between images, just to experiment.
When I examined the LOW image of each bracket, I saw that the -2.7ev exposure was darker than the -2ev as expected. The difference was not large, but was noticeable. However, when I looked at the image properties of this file (through either Windows or Photoshop), I found to my surprise that the aperture, shutter time, and ISO were all identical for the two images (aperture: f/22, shutter time: 1/60, ISO:100). On the other hand, when I looked under Windows at Properties->Details -> Exposure bias for these files, it said correctly "-2.7 step" or "-2 step." But none of the physical exposure parameters were changed!
How can the camera produce two differently exposed images of the same scene with the exact same exposure parameters? I thought that the only things the camera could change to modify the "brightness" of a photograph was aperture, shutter time, and ISO. So if all three are the same, why is the final picture coming out at a different exposure?
This is really puzzling me. The only thing that I can think of is that the camera IS taking the exact same image for both cases because the physical parameters are identical. Perhaps the -2.7ev exposure is undergoing some post-process in the camera (kind of like the ISO gain) that is darkening the image to match the photographer's desired intention of -2.7ev. But there is really no new "information" in the -2.7ev that isn't in the -2ev. But that explanation doesn't make a whole lot of sense to me.
Does anyone have any ideas? Thanks in advance.