FF low-light advantage vs. crop?

Folks, I understand that the 5D I & II are better performers in low light when compared to Canon's XXD crop-body line. Some of this has to do with sensor size. Is there any way to quantify that advantage, say, the 5D II's FF sensor gives one full stop advantage over the 50D in low light conditions?

I know the sensor design and internal processing affects this as well, but I wanted to see if there was an established rule for the sensor size itself.

The 50D offers some pretty dang good high ISO performance. The 5D2 is better, probably by a couple of stops.

No rule, just people doing testing. Bigger pixels are cleaner, but sensor technology advance too. Kinda jealous that you are in New Braunfels. I spent 12 years in Austin and miss the scenery.

Yeah, New Braunfels is quite a photogenic town. I work in San Marcos, which ain't half bad, either!

jblaschke wrote in post #9470115
Folks, I understand that the 5D I & II are better performers in low light when compared to Canon's XXD crop-body line. Some of this has to do with sensor size. Is there any way to quantify that advantage, say, the 5D II's FF sensor gives one full stop advantage over the 50D in low light conditions?

I know the sensor design and internal processing affects this as well, but I wanted to see if there was an established rule for the sensor size itself.

Sensor size is totally irrelevant. Photosite (loosely termed "pixel") size matters.

Generally I hear people say that you get 1 more stop out of the 5D than the 40D/50D, and another out of the 5D II. I guess that has been pretty much true for me. With the 40D I pretty much just used Auto ISO and never had any trouble with ISO 800. With the 5D I can bump it up to 1600 and still feel just as good about the images.

I have also heard people say the noise is more pleasant on the 5D. I haven't shot enough high ISO with it to have an opinion on that part.

I honestly don't know much much of a difference there is. People with FF cameras seem to rave about the greatness of larger photosites but from some reviews and tests I have seen, there is close to no difference.

xarqi wrote in post #9470210
Sensor size is totally irrelevant. Photosite (loosely termed "pixel") size matters.

So since the 5DII has the same pixel size as the 30D it = the 30D??

I think there is a little more to it that photosite size, and sensor size does come into play (since you can fit more pixels on a larger sensor).

bacchanal wrote in post #9470533
So since the 5DII has the same pixel size as the 30D it = the 30D??

That does not follow from my statements.
Several things contribute to low light performance, including photosite size, however sensor size is not one of them.

xarqi wrote in post #9470639
That does not follow from my statements.
Several things contribute to low light performance, including photosite size, however sensor size is not one of them.

M'kay, I'm not sure how you can say sensor size is totally irrelevant.

More pixels, larger pixels, less enlargement...these things are accommodated by a larger sensor, at least when you consider the design of the camera as a whole.

There is a physical difference on a per-frame basis due to the difference in sensor size.

For full frame versus crop, the difference in high ISO performance will be about 1.3 stops in favor of the full frame camera. This is assuming the sensor technology used for both cameras is identical.

Beyond that, the differences will be attributable to the differences in the sensor technology being used. The 5Dmk2 probably gets somewhere between 1.5 and 2 stops improvement over the 50D in terms of high ISO noise based on the comparisons I've seen, which suggests that the 5Dmk2's sensor tech is a little better than that of the 50D.

Now, keep in mind, that's with per-frame noise. You can't determine per-frame noise by examining 100% crops, because a 100% crop only tells you what the per-pixel noise looks like, and that is a function of the size of the physical pixels. The size of the physical pixels, combined with the physical size of the sensor, can be used to determine the resolution of the sensor.

Consider the 50D and the 5Dmk2. The 5Dmk2 is a 20 megapixel camera with a full-frame sensor. The 50D is a 15 megapixel crop camera. If one were to build a crop sensor with the pixels from the 5Dmk2, they'd get an 8 megapixel sensor because of the difference in sensor size. The 50D's sensor packs nearly twice the number of pixels into the same area as the 5D2's sensor, so the 5D2's sensor is gathering twice as much light per pixel as the 50D. Which means the 5D2 has a 1 stop advantage over the 50D on a per pixel basis from the pixel size difference alone. Since the 5D2's sensor seems to be a little better than the 50D's in terms of the technology (since its performance exceeds the difference you'd expect due to the physical sensor size difference alone), it follows that on a per-pixel basis, it'll actually be doing a little better than one stop over the 50D on a per-pixel basis -- somewhere between 1.2 and 1.7 stops.

If all that sounds confusing, just think of it like this: the difference in per-frame noise is determined by the difference in sensor size and the difference in the tech. The difference in per-pixel noise is determined by the difference in the pixel size and the difference in the tech. Either way, unless there is a very large difference in the tech, the difference is going to be dominated by how much light can be gathered, either on a per-pixel basis or a per-frame basis.

The per-pixel noise is most useful when determining how a crop from a high-ISO shot will look. The per-frame noise is more likely to be what you really care about in the end because it will determine how the overall shot looks. The latter is why the claims that the 40D's high ISO performance equals or slightly exceeds the 50D's are misleading: they're based on examining the per-pixel noise, while the 50D's resolution exceeds the 40D's by a factor of 1.5. If the per-frame performance of the two cameras were the same, then the per-pixel performance of the 50D would be worse than that of the 40D by nearly 2/3 of a stop. Conversely, if the per-pixel performance of the two is about the same, then the 50D's per-frame performance would win by nearly 2/3 of a stop.

jblaschke wrote in post #9470115
Folks, I understand that the 5D I & II are better performers in low light when compared to Canon's XXD crop-body line. Some of this has to do with sensor size. Is there any way to quantify that advantage, say, the 5D II's FF sensor gives one full stop advantage over the 50D in low light conditions?

I know the sensor design and internal processing affects this as well, but I wanted to see if there was an established rule for the sensor size itself.

Have you checked out dxomark?

http://www.dxomark.com …/Canon/%28brand​2%29/Canon

I don't know about their methods or validity, but it's quantified.

Hmmm - "per frame noise", you say? Maybe I'm missing something here.

Google to the rescue - I'll do some reading.


Oh.


My google search for "per frame noise", reported 6,280 hits, although only 37 links were provided. I saw only 6 related to photography, 4 of these being at POTN from kcbrown. There is 1 usage at canonrumours.com from user "ashish", and 1 at photo.net pertaining to noise reduction in DPP.

In contrast, when I searched for the first random concept that came to mind, "blue aardvark", I got 47,500 hits, with 1000 links provided.

I conclude that blue aardvarks are much more common than "per frame noise".

If I google "wrong answer", I get 947K results, so I conclude that there are many more wrong answers on google.

xarqi wrote in post #9472760
Hmmm - "per frame noise", you say? Maybe I'm missing something here.

Google to the rescue - I'll do some reading.


Oh.


My google search for "per frame noise", reported 6,280 hits, although only 37 links were provided. I saw only 6 related to photography, 4 of these being at POTN from kcbrown. There is 1 usage at canonrumours.com from user "ashish", and 1 at photo.net pertaining to noise reduction in DPP.

In contrast, when I searched for the first random concept that came to mind, "blue aardvark", I got 47,500 hits, with 1000 links provided.

I conclude that blue aardvarks are much more common than "per frame noise".

LOL!

I don't know of a better term to use for what I mean.

Take a shot with one camera. Take the same shot (same settings and everything) with another camera. Size them to exactly the same size (which is what you'd be doing if you printed them both to a particular paper size). Then compare the two shots in terms of how strong the noise appears to be.

That is a per-frame noise comparison: you're comparing the total noise in the frame, not the noise from a 100% crop.


Hope that explains what I mean...