Correct me if I'm wrong!

steveo_mcg said:
Large format guys must be able to shoot iso 1 at night by that logic.
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That's where the extra image quality comes from. The ISO and DoF aspects of it are all explained in the DPReview article I linked. The other part is lens MTF that is even less well understood - the extra sharpness obtained with larger formats, that is almost all to do with format size and not pixels. I've explained that often enough too, but happy to repeat :)
 
HoppyUK said:
No. There's a net gain of over one stop ISO with FF vs APS-C
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The only way that could be the case is with full frame and APS-C sensors with the same number of pixels. In that case, the individual photosites on the APS-C will have half the area and collect half the light compared with the FF sensor.

That's like having a 35mm frame of ISO 100 film compared with a medium format frame of ISO 200 film though

However, a 12MP APS-C sensor should have the same sensitivity as a 24MP FF sensor.


Steve.
 
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Steve Smith said:
The only way that could be the case is with full frame and APS-C sensors with the same number of pixels. In that case, the individual photosites on the APS-C will have half the area and collect half the light compared with the FF sensor.

That's like having a 35mm frame of ISO 100 film compared with a medium format frame of ISO 200 film though

However, a 12MP APS-C sensor should have the same sensitivity as a 24MP FF sensor.


Steve.
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No again. I know where you're coming from, but the noise/ISO limit is ultimately determined by photon collection, and that in turn is determined by format area - not the size or number of the pixels.

Read that link to DPReview. Plenty of examples there too ;)
 
This from the article is how I understand it
This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.
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and people might be getting confused.

The aperture equivalence is to explain what the depth of field would be like on a 35mm (FF) camera and the focal length equivalence is to explain what the angle of view would be like on a 35mm (FF) camera

Mike
 
Who the hell opened this can of big a*sed worms!?!?!?!? :S
 
I don't see how just increasing the area of the sensor makes it more sensitive. It doesn't work for film. A 6x9 film back on a 5x4 camera has the same sensitivity as a 5x4 sheet of the same film. So I don't see how it works if you bolt on extra areas of sensor.


Steve.
 
Steve Smith said:
I don't see how just increasing the area of the sensor makes it more sensitive. It doesn't work for film. A 6x9 film back on a 5x4 camera has the same sensitivity as a 5x4 sheet of the same film. So I don't see how it works if you bolt on extra areas of sensor.


Steve.
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Think of it in terms of total photon collection instead of sensor/film per sq mm and it makes perfect sense. Photon collection is key - the reason why high ISO has more noise than low ISO, and why larger formats are always less noisy than smaller ones. Those are hardly contentious statements.
 
steveo_mcg said:
Large format guys must be able to shoot iso 1 at night by that logic.
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Steve Smith said:
I don't see how just increasing the area of the sensor makes it more sensitive. It doesn't work for film. A 6x9 film back on a 5x4 camera has the same sensitivity as a 5x4 sheet of the same film. So I don't see how it works if you bolt on extra areas of sensor.


Steve.
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There's no difference in exposure. If there were, all hand held meters would only be accurate with one film format. As I can use my hand held meter with 8x10 inch film, or APS-C with equal facility, this is obviously not the case.

There are differences in apparent depth of field with sensor size, due to magnification factors, but exposure remains the same. Set 1/60th at f8 on a Nikon d7200, and the exposure will be the same as 1/60th @ f8 on a D800 when using the same lens, but apparent depth of field will be different (although in reality it's identical).


With digital sensor, yes, larger ones are usually more sensitive, but by the time you get your hands on it once installed in a camera, it will be calibrated accordingly so your light meter will work as usual.

Hoppy, as usual, is kind of correct, but as usual is not giving any context and confusing people. :)


Relax guys.... so far as exposure goes, there is no difference between formats.

As far as FILM goes.. I can expose a piece of 5x4 film at 1/60th @ f8, get a correct exposure, then take an identical piece of film, cut a 35mm size piece out, stick it in a 35mm camera, and use exactly the same settings.
 
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Hoppy is getting technical with no context as usual.

A bigger sensor is more sensitive, sure... but by the time you get hold of that sensor, it's wrapped in a camera, and the system calibrated to known EV values.


This is an argument about nothing :)
 
HoppyUK said:
Think of it in terms of total photon collection instead of sensor/film per sq mm and it makes perfect sense. Photon collection is key - the reason why high ISO has more noise than low ISO, and why larger formats are always less noisy than smaller ones. Those are hardly contentious statements.
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Yes but the photons hitting the pixels doesn't change. Each pixel is either charged or not. The pixels in small formats are simply closer together and generally fewer so random signal noise becomes a larger part of the image. Therfore the image appears noisier.

Pookeyhead said:
There's no difference in exposure. If there were, all hand held meters would only be accurate with one film format. As I can use my hand held meter with 8x10 inch film, or APS-C with equal facility, this is obviously not the case.

.
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Exactly fp4 is the same emulsion and the same sensitivity whether it's cut to tiny little 35mm or some mental ulf.

Like you say the sensors are calibrated to the iso standard. Thus the term standard.
 
There are differences in sensitivity in digital sensors due to size because pixel density comes into play, but film is film. It's made as one emulsion, and cut to various sizes. The size and density of silver halide in that emulsion is identical regardless of format, hence ISO400 film is grainy at 35mm size, and grain free at 5x4" size.

It really is as simple as that.


While a D800 sensor is more sensitive than a D7000 sensor, it is calibrated by the firmware to behave identically with regards to exposure. This is why larger sensors offer less noise at the same ISO.


Again... it's as simple as that.


/thread.
 
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HoppyUK said:
The amount of light received by the sensor will be the same on a per-square-mm basis, but the total amount of light collected and delivered will be more than double on the full-frame sensor - because the sensor is either 2.25x or 2.56x larger in total area, according to1.5x or 1.6x crop factor (area is crop factor squared). In round numbers, FF is twice the size, so gains one stop ISO advantage and one stop less depth-of-field at same f/number.
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"One stop ISO advantage" is only in terms of total light gathered. ISO in digital photography is the sensor signal gain, so what you are saying is correct if you replace ISO with total light gathered, but wrong if you use ISO where ISO is associated with the camera setting. You can't achieve the same photo with full frame at ISO 100 and crop at ISO 200, the full frame will be one stop under exposed.

Basically we agree with eachother, except you made this more complicated by introducing total light gathered (which doesn't matter when ISO is standard across all cameras) and confuse it with word ISO.
 
wuyanxu said:
Basically we agree with eachother, except you made this more complicated by introducing total light gathered (which doesn't matter when ISO is standard across all cameras) and confuse it with word ISO.
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And using the term "equivalents" - sometimes as useful as 'Shoe Sizes' - UK, US and EU have their own system/rating but they never seemed to be the same fit when you buy them in another Country :)
 
Pookeyhead said:
<snip>

Hoppy, as usual, is kind of correct, but as usual is not giving any context and confusing people. :)

<snip>
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Absolutely correct actually :D

No context? I linked to an extensive article that explains all this. It's a tricky subject, seemingly contradictory in parts, that can't be covered in a couple of sentences.
 
HoppyUK said:
seemingly contradictory in parts, that can't be covered in a couple of sentences
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Maybe there's a reason for that!

I read through that lot and whilst plausible in parts it had a kind of "religious credo" to it.... of the sort "I'm going to make this doctrine; you will believe it" There also seemed to be a degree of obfuscation around the more controversial areas.

Perhaps my creed of Physics and Logic is at variance with the author at DPReview.
 
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