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| p.3 #2 · Sigma 18-35 f/1.8 hands-on and samples online |
Actually DOF works the other way when enlarging. Since crop sensor images have to be enlarged more, the circle of confusion gets bigger and therefore the depth of field is reduced. However the angle of view comes to rescue (like you said) because instead of 75mm I have to shoot with 50mm to get the same frame, and 50mm has better DoF, so the end result is that we get more DOF.
You're right, I misspoke about enlargement. It was late and I was jumping back and forth to make sure I wasn't messing up but still did
Why shoot at the same shutter speed. Why not faster?
Because we're trying to achieve the same photo with DX and FF in this exercise. I understand that higher shutter speeds are desirable in low light conditions, but the same higher shutter speed can be achieved with both DX and FF. It's just a matter of whether you're increasing aperture or ISO to compensate.
This is why I am personally interested in this lens. In poorly lit family rooms, dance halls, sport gyms, where action is happening, I can use all the light that is available to keep my shutter speed high and eliminate subject blur. As long as the focal length works for me, I have no qualms in shooting DX to get the faster shutter speeds. True, if printed at 40x60 the images will be noisier, but noisier images are a hell of a lot better then blurry images. Noise can be removed, details can be recovered, but so far there is no...Show more →
Note here that you agree that the DX will be noisier. Then you said:
First of all, in my given scenario, of D800 DX/FX, noise is the same.
So is DX noisier or not in your view? Not sure where you actually stand since you said it would be noisier when printed but here you're saying the opposite.
I'm going to assume that the only thing you disagree with is the 1 stop difference in noise between DX and FF assuming one is trying to create the same exact image with both. This is very easy to verify for yourself if you really want to. Use the settings to achieve the same image as we discussed then compare both images fullscreen on the same monitor or 2 same sized monitors. Use a sufficiently high ISO because otherwise modern cameras are so clean at even medium ISO that you'll be almost noiseless in both images.
You have the ideal camera to test with since it's FF with a DX mode--the D800--and can shoot with the same camera and just attach the right lens for each shot or use the same zoom lens and change the zoom between shots. The same test could be run with any FF camera by just using a shorter lens and cropping to simulate DX mode, although there'd be more math involved to figure out how much to crop instead of the camera doing it for you
D800 - D300 = way more than one stop difference
D7100 - Canon 5D = Same level of noise
D7100 - Canon 1Ds Mark I = D7100 beats the pants of this first generation full frame
Fuji X-Trans (what is noise?)
Olympus OM-D - Canon 5D = about same
Why are you comparing different cameras let alone different generations? As I said before it's all other things being equal so you compare the latest tech, and even then comparing different cameras is dicey because of a number of factors. In any case it's not necessary since you can do it all in your D800.
Bottom line for me: the new Sigma brings APS-C in line with FF in terms of getting usable shots in low light. Actually there's one potential benefit it brings over FF: with the larger aperture the AF sensors see more light at f/1.8 than they do with an f/2.8 lens on FF, so AF could be better! In any case it's a very exciting lens, and Canon should take note instead of just doing Mark II lenses.