FF vs. APS-C - Aperature Behaviour

[DavidEccleston]

Jon, I think the noise issue is a separate argument. Sure FF tends to get less noise, but that

[clemmb]

If a crop camera had the same sized pixels on the sensor as the full frame, the noise would be the same (though your resolution would be low!), so the crop factor doesn't have a directly correlation to pixel noise.
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Same pixel size but different noise.


Am I missing something in your statement?


Mark


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[Kamelot]

Sure FF tends to get less noise, but that's due to more photons hitting
the a single pixel over the same time, as the pixels are larger. If a
crop camera had the same sized pixels on the sensor as the full frame,
the noise would be the same (though your resolution would be low!), so
the crop factor doesn't have a directly correlation to pixel noise

Nope, you are not right. Here was discussed several times about sensor size and what depends on it.


And clemmb shows for you good camera comparison.


FullFrame sensor will have less noise not due to larger pixels, but due to larger surface of sensor = larger sensor, which can collect larger amount of light.


Imagine, you have:

1. 10 buckets with 10 <span class="HW"]litre capacity each<span class="HW"]
2. <span class="HW"]25 buckets with 5 <span class="HW"]litre capacity each.

And you place each type of bukets one nearby others. You have 2 areas with different size of buckets and of course different size of covered area. When the rain is starting, think, which area of buckets can produce larger amount of watter?


I think you will do the math []


<span style="color: #ff0000;"]Edit: <span style="color: #ff0000;"]and it is due to overal larger capacity of buckets (pixels) = larger sensor.

It's the DOF increase, due to changed camera to subject distance
required to get the same framing, that makes people talk about the crop
factor applying to aperture, as they are directly linked.

So tell me, when here http://www.dofmaster.com/dofjs.html i select:

• 5D, 135 mm, F/2 and distance 5 meters, and i get 16 cm of DoF
• and with 7D, i select 85 mm (for same framing), F/2 and 5 meters distance, i get 26 cm of DoF.

Which number (Depth of Field) is smaller (more narrow): 16 cm or 26 cm ? []

[DavidEccleston]

I

[neuroanatomist]

DoF is determined by four factors: aperture, focal length, subject distance, and circle of confusion. Only the last one is different with sensor size, but I

[DavidEccleston]

I'm adding more just to get back to the original argument.


As I mentioned, the noise should be identical in the middle of the frame, at a pixel level. Therefore nothing to do with effective apertures, a seperate argument. The extra size gives you less noise in prints to due extra pixels, shrinking the noise, or letting you downsample it away. I'm not saying there is no advantage to FF, just that the noise advantage has nothing to do with effective apertures.


With these same two cameras, though, adjusting your distance, or your lens, to produce the same framing, will have different DOF. This is an effect which is visible at the pixel level. This effective aperture change affects the ENTIRE FRAME. This is a FF advantage due to effective apertures.


edit: slight rewording of noise summary.

[neuroanatomist]

RE: I

[clemmb]

The per pixel noise is identical with identical pixel sizes, but as you have more pixels, the effect of the noise is lessened.
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Agree. I was not understanding your first post on this. We are in agreement.


Mark

[Kamelot]

I'll argue that we're both right about noise, because I think we were looking at it in different ways.


Both cameras have the same pixel size and bits per pixels, so the buckets aren't 5 and 10 litres, they're both the same. I wasn't arguing about the total light captured, but the total captured per mm, or per bucket. The same amount of water will be captured in the center buckets in each case, as they're the same size and depth. That's what makes me right.


Due the the extra buckets, you can downsample, and get the effect of less noise (Daniel had a whole big thread all about it), but at the original capture size, the noise is identical at the pixel level. Or due to the extra resolution, when printed, any noise will be rendered smaller, and thus less visible. That makes you (and DxO) right.

Yeah, maybe i wasn't reading your post carefuly. Maybe you were saying some truth []


I know that Daniel's thread about all pixel size and dependency of that. In previous post forgot to mention the key think. I already edited it.


And in my opinion, the pixel size doesn't matter if the overal pixel surface is larger.


It does'nt matter if you have 1,6 square metre and you will split it to the 10 smaller squares or to the 20 squares . It still will be the same 1,6 square metre surface. And if you will compare it to the only 1 square metre surface, does not matter, how large the squares on that 1 square metter will be. The overal surface capacity will be smaller. Bigger surface can collect more light, and the noise is smaller. That's what i wanted to express []

It all depends on how you're measuring the noise. The per pixel noise
is identical with identical pixel sizes, but as you have more pixels,
the effect of the noise is lessened.

Yes, i agree. And want to add.. like were said in that big thread, that you can not compare pixels one by one (if this
is larger - good, smaller - worse). One pixel does not do the job. The
picture comes from collection of pixels.

[DavidEccleston]

Yes, I muddied things up by bringing up pixel level arguments without saying why. By showing the noise is equal at the pixel level, I show that the noise advantage of FF is due to pixel size and/or the bonus pixels at the edge. Is has nothing to due with effective apertures, which was the whole point of my original post. The noise advantage is a separate argument. The effective aperture argument is all about DOF changes. Jon pointed out a nice benefit of FF, which had nothing to do with the original question, and I just wanted to point that out (and then defend my argument when everyone said I was wrong ).