In which ways, and why, are smaller sensors more efficient than larger? Part 2

Started Feb 23, 2014 | Discussions thread
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Anders W OP Forum Pro • Posts: 21,465
The practical utility of sensor efficiency

This is a response to Sergey_Green's post here in a recently expired thread on the same topic as the present one.

Sergey_Green wrote:

Anders W wrote:

While that example was posted to show that and why shadow noise is a problem rather than to show the greater efficiency of one sensor size than another, it works for the latter purpose too. You could not have used the same f-stop on FF without making the DoF too shallow and (as I hope you agree) this is a shot where'd you'd want everything to be sharp across the frame.

Many of the images you post (most of) are shot from a distance. There are no close foregrounds, with the main objective further away, and there are no depths to capture.

You got that wrong. While the images I post here on DPR are certainly not a representative sample of my photography, most of them are nevertheless either such that I am at the limit in terms of DoF or they are shot in scenarios where light is abundant or shutter speed not a problem (and the question of sensor efficiency for equivalent images therefore not of much interest). If you think you can show systematic evidence that the above claim of mine is not correct, let me know what that evidence is. Links please.

The particular example we are discussing (originally posted here) is a case in point. That was shot with my Minolta MD 85/2 on my E-M5, either wide open or at f/2.8 (I don't remember which but I remember trying to go as wide as I could) at a distance of about 20 meters. That gives me a DoF of three to five meters, and I certainly needed that in this case to get both the cupola and the ceiling beneath it (sloping downwards on all sides) as sharp as I wanted them, particularly since I prefer to set focus in a scene like this on the central point of the image (the ceiling inside the cupola) rather than somewhere inbetween the most distant and the most proximate point (which would compromise the sharpness of the central point somewhat). So an FF user would have had to stop down to f/4 or f/5.6 to get the same.

Like most of the images in bad light that people post.

What evidence can you muster in support of that sweeping generalization? Links please.

Which means you could use say f/5.6 with standard zoom on one camera as you could use exactly the same on the other. The only argument you could bring to this is which lens performs better at what stop. Which, in turn, makes this whole debate even more restrictive in real shoot situation then it first appears.

For reasons already explained, you are wrong about that.

I do for reasons already explained: Provided that we don't clip the highlights (and it seems we agree that we shouldn't), the shadows are the most problematic part of the image with regard to signal-noise performance. The highlights will look just fine.

No, not really, the shadows are hardly problematic in most cases.

I am not saying that the shadows are a problem in most cases. What I am saying is that if you have problems, they'll show up most strongly in the shadows (provided that you have exposed correctly so as not to clip any important highlights).

But if you start pushing things around, the blue sky will show signs of posterization well sooner (and show real problems in most cases) and well before the viewer start even looking at shadows.

Please give us an example, including a link to the associated RAW file, of the situation you describe on the preceding two lines.

Shadows is a problem, or it can be a problem, but it is not as big a problem as you are trying to make it.

See above.

But this is not a premise with regard to the efficiency issue since my analyses show smaller sensors to be more efficient with regard to the highlights too (greater normed max SNR).

And for the reasons that no-one knows, and so what?

The reason that I show results not only for the shadows but also for the highlights is that some people appear to worry about the latter. You for example. Don't know why you would want to complain about the fact that I address your concerns.

Purely academic debate, you like this kind of stuff, don't you .

As I think most people on this forum are already aware, I like to discuss technical issues that have practical implications (e.g., for the choice of camera gear). The present discussion is but one example.

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