jonrobertp: Go to FF ? Nope. You lose too much lens reach w your longer lenses. And then wt. & cost. For a lighter more $/wt. efficiency...this lens is a very good addition to a shooter doing much low light shooting.
You do not get any extra lens reach on APS-C. You may take exactly equal APS-C crop from the FF image at the same focal distance. The "equivalent focal distance" is meant in terms of the perspective/angle of view, not the reach/resolution.
F1.8/APS-C/ISO100 is about the same as F2.8/FF/ISO250 both DOF-wise and light-wise. Modern FF sensors have about 1.5 stops advantage in SNR over the APS-C sensors, so with F1.8 on APS-C you will have about the same SNR (at the same shutter speed) and DOF as with F2.8/FF. As simple as that.
However:- only 2x zoom compared to 3x F2.8 for FF- the resolution (in lpph) is going to be lower as always with APS-C. - price compared? The optical design is very complex, not speaking about virtual F1.8 3x zooms.
If you save on an APS-C body, you can not have the same overall performance for the same lens price as you would have with FF (subject to the particular manufacturer's pricing policy, but Sigma is not going to be cheap in any case).
igor_s: For me, small size is not an advantage, as long as this is not a pocketable compact. Even for my medium-sized man hands, I would prefer rather 5D over 700D (price aside:). A second camera for a miniature woman-pro? Non-pros, I guess, would prefer a mirrorless system or a compact.
I think that Canon do not expect high sales, but the cost of redesign is very small, and they simply want to sell a little more old chips. Just the same as with 700D.
What actually draws attentiion is the lens if it is not too small against the body. Sure, if you are going to use the 3x kit lens...
For me, small size is not an advantage, as long as this is not a pocketable compact. Even for my medium-sized man hands, I would prefer rather 5D over 700D (price aside:). A second camera for a miniature woman-pro? Non-pros, I guess, would prefer a mirrorless system or a compact.
I would like to clarify some points concerning the "equivalent focus distance" with DX vs FX sensor size.
With given focal length and shooting distance, the image on any sensor (as well as on paper:) is geometrically THE SAME. And with different f the images will be different. The consequences:
1. If you shoot a small distant object, you DO NOT get any "boost" with a DX sensor. To get the object's image bigger/more detailed, the only option is to use a longer lens (the sensor quality aside).
2. If you use the "equivalent" lenses (say 50 mm with DX and 75 mm with FX), the perspective in the central DX area will look different. The rectangles drawn on the picture show the frame borders with different focal lengths, but the picture itself does not remain the same!
3. With the FX sensor, you can simply crop the frame to get exactly what you would get with a DX sensor using the same lens. In this case you can even use DX-dedicated lenses if your FX camera will accept them.
PeterQ: I wonder how everyone presents his/her pictures.Is it on screen (36 Mpix?)Is it on paper (20x30 inches or more)? Wat lights are used to present them?At the end, the quality is what I perceive when the pic is shown, not what the computer says.Some judgements appear to represent more emotions than facts.
On screen you can zoom in to infinity, or you can crop for the print. So there is sense in many GOOD megapixels. However, very few (if any) lenses are sharp enough to validate 36 MP on a FF, and only in the center of the frame and in the very limited range of apertures.
About too much emotions in some posts, I am quite agree (and that's gently speaking).
igor_s: In RAW mode, the difference between MkIII and 600D is even less than 2 stops. Compared to MkII, there is no improvement at all. (Well, maybe half a stop if we reduce to the same number of pixels). Again, D800 does poorly, just slightly better than 600D (or less than 1 stop better if reduced).
According to DxOMark, as far as I can remember, the SNR at 18% gray remains in the "excellent range (>38 dB) for D800 at ISO up to about 600, whereas for the 600D only up to about 150. That's 2 stops diffrence, or about 2.5 stops if reduced to the equal pixel counts. This result is quite different from what I could see on the photos in the preview. It is close to what the MkIII showed here, which I think is more viable.
Note that for the MkIII the DxOMark data is so far unavailable, and the D800 started selling much ealier. So at this point I would not say about the superiority of either model. We need to see more technical data as well as more real-world images.
First of all I would like to stress that I said ONLY that the D800 result (meaning the particular sample at the particular site) was quite unexpected. I did not say that this camera is bad.
Let us take the figures from DxOmark. I am speaking ONLY about the SNR, not about the colour depth of something else that adds to their final sensor score. This is because the colour depth and the tonal range for (almost?) all sensors remain "excellent" at much higher ISO values than the SNR does. The quality of the photos at nigher ISOs degrades almost exclusively due to the SNR drop. (to be con'd)
Everything but motion rendering? i do not believe that you can have a decent video at 25 fps (if you do not prefer the cinema to the real life).
In RAW mode, the difference between MkIII and 600D is even less than 2 stops. Compared to MkII, there is no improvement at all. (Well, maybe half a stop if we reduce to the same number of pixels). Again, D800 does poorly, just slightly better than 600D (or less than 1 stop better if reduced).
For MkIII, SNR is about the same at ISO higher by 2 stops than for 600D. Expected for the latest FF. With D800, something is wrong. At ISO 800 the picture was not better than with 600D. Even softer while not less noisy. Quite unexpected. (In all cases, I looked at the girl's face. IMHO the fragment chosen by default is not suitable for the noise levels assessment).
Useful info, BUT...
IMO the real beauty is in NATURAL skin, hair etc. The purpose of makeover is to HIGHLIGHT the beauty, not to mask bad-looking things. It you do not like your object, better do not shoot (unless you are after money). Or you could put a rubber mask on the model's face, that'd be perfect...