Originally Posted by Vince
In low light, the FF only gets more light if you shoot it at a thinner DOF. If you use the same DOF, then the light, too, is the same. FF is no more or less difficult to get sharp photos in low light. In the case of the 7D vs 5D2, I would say the 7D has the advantage due to better autofocus.
No, this is incorrect as it pertains to exposure. For simplicity*, the amount of light per unit area reaching the image plane is determined by effective f-number and shutter speed. It is independent of the total area of the imaging sensor. It is also independent of ISO, which corresponds to the sensitivity of the imaging medium to incoming light.
That is to say, if you have a 5D Mark II and a 7D, and each is set to take an exposure of f/4 @ 1/100s @ ISO 100 @ 50mm of the same subject from the same distance, the resultant images will have the same exposure level. The only difference is that the 7D will show a narrower angle of view.
*for the pedantic, this should be effective t-number, not f-number.
Great post, one minor comment:
You are correct that "exposure" is independent of the total area of the imaging sensor. But exposure is not the only factor to consider when it comes to low light. The most important factor is "total light", which is a home-made term for "light per area times total area". The 5D2 and 7D have the exact same sensor performance per area, but the 5D2 has far more area. So if you give them the same exposure, the 5D2 will end up with more "total light", which results in far less noise (and more dynamic range).
For example, a 3.6x2.4mm mobile phone camera with a 5mm f/2.8 lens has the exact same angle of view and exposure as a 36x24mm sensor (5D2) with a 50mm f/2.8 lens. But the total amount of light is 10 stops higher in the 5D2, and that's why it has far less noise than a mobile phone camera in low light.
You probably know all this already, I only responded because your comment made it sound like exposure was more important than total light when it comes to low light.
Kind regards,
wanna know if it's your lens or your hands, that's easy. Just take a shot with your camera mounted on a sturdytripod, IS off, ISO 100,use the timer to trigger the shutter. If the shots come out tack sharp, it means you need to work on your handholding technique.
To me, the right side of the box looks plenty sharp for being wide open at 2.8 and at ISO 3200. that high of an ISO should degrade the picture somewhat, although I don't have a new canon model, so I don't know how drastic the improvements are for high ISO.
finally
rule with image stabilization, if youre shooting with tripod or from any fixed and stable surface IS must be off...
The "kit" lens for a 5DmkII is usually a 24-105L, pretty darn sharp to begin with. The 17-55 isn't terribly sharp at f2.8 to begin with either.
Easy test: try his lens, and see if you get the same results.
If that jerk would come see me I just might try out his lens...but...lets not get into that.
I thought that the 17-55 is supposed to be sharp wide open.
"This lens is sharp! Wide open and from edge to edge. Unless the distance is close that is - I'm finding that close subjects do not produce the same image sharpness as normal distance subjects." according to the review on this site...
So my question now, is what is normal distance versus close? I tried to gauge using the lens but i'm still a bit lost...
Check out the comparison of these two lenses at 2.8. I know they are on different bodies, but the 16-35L is much sharper at 2.8, yet both are reasonably sharp wide open.
http://www.The-Digital-Picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=398&Camera=474&Sample=0&am p;FLI=4&API=0&LensComp=412&CameraComp= 453&SampleComp=0&FLIComp=4&APIComp=0
I think you are mistaken. If you were to put the 16-35 on the 50D, you would find out that the 17-55 is sharper than the 16-35. Read Byran's review:
<p style="padding-left: 30px;"]
My Canon EF 16-35mm f/2.8 L USM Lens
is slightly sharper in the center at 17mm wide open, but the Canon EF-S
17-55mm f/2.8 IS USM Lens is sharper at all other tested focal lengths
- and proved much sharper in the corners at all focal lengths and
apertures.
Distortion was also less on the 17-55.
In my opinion, the only reasons to buy the 16-35 over the 17-55 are for
full-frame compatibility (a big reason), better build quality and
environmental sealing (EF-S compatible bodies are not weather sealed at
this time).
Your mistake was using the charts incorrectly. That is why Bryan specifically points out that charts from different bodies cannot be compared for lens performance.
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