Beginner Crop vs FF

Sean83

Sean83

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Sean
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This might be a silly question and sorry if it is,
I want to know if you take the same picture on a crop and FF at let's say 5.6f and same shutter speed and iso would the FF be a brighter picture because of the bigger sensor?
Thanks sean
 
Um no!
 
Sean83 said:
brighter picture because of the bigger sensor?
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Euuuhh… nope, for sure!

ƒ5.6 is the same ratio to available light
in both cases and for both sensor size.
 
Thanks guys, as I said sorry for the silly question.
 
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There are not such things as silly questions…
there may be some silly answers though! ;)
 
I wasn't being sarcastic? I was guessing .......
 
Sean83 said:
This might be a silly question and sorry if it is,
I want to know if you take the same picture on a crop and FF at let's say 5.6f and same shutter speed and iso would the FF be a brighter picture because of the bigger sensor?
Thanks sean
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The answer is no, but it's far from a silly question, because the larger sensor does indeed collect more light - when comparing a subject framed the same, from the same distance, with focal length adjusted. However, the way this pans out is the full-frame image shows less noise (when comparing similar generation sensor technology).

There are other changes too: depth of field is reduced in the full-frame image by a fraction over one stop, and the full-frame image will also be sharper (regardless of pixel count).
 
HoppyUK said:
The answer is no, but it's far from a silly question, because the larger sensor does indeed collect more light - when comparing a subject framed the same, from the same distance, with focal length adjusted. However, the way this pans out is the full-frame image shows less noise (when comparing similar generation sensor technology).

There are other changes too: depth of field is reduced in the full-frame image by a fraction over one stop, and the full-frame image will also be sharper (regardless of pixel count).
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I like this explanation. Brightness is function of intensity (light 'concentration' at given point on sensor). Intensity stays the same between crop and FF but the larger sensor means more light/charge collected which means more energy output from the sensor.
 
When talking about noise one has to keep pixel size in mind, meaning that you only get less noise when keeping pixel count the same for APS-C and FF in that comparison.
 
madsector said:
When talking about noise one has to keep pixel size in mind, meaning that you only get less noise when keeping pixel count the same for APS-C and FF in that comparison.
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Recent examples prove that pixel size/density/numbers are not an overriding consideration, or even a particularly significant one. Key factors that determine noise are sensor area and technological development.
 
Ok, what I ment is that if you fill an APS-C sensor and a FF sensor with pixels of the same size (and same technological development state) you will get two images with same noise (both pixels collect same amount of light) but the FF one has higher resolution. That is just physics and the opposite side of viewing at it while the generalizaton "FF collects more light and needs less amplification" remains still true.

I just wanted to mention that for noise you always have to look at the pixel count as well as for sensor generation and overall size. Although it's not easy to find examples for that since between sensor generations usually technology and pixel count improve at the same time...
 
madsector said:
Ok, what I ment is that if you fill an APS-C sensor and a FF sensor with pixels of the same size (and same technological development state) you will get two images with same noise (both pixels collect same amount of light) but the FF one has higher resolution. That is just physics and the opposite side of viewing at it while the generalizaton "FF collects more light and needs less amplification" remains still true.

I just wanted to mention that for noise you always have to look at the pixel count as well as for sensor generation and overall size. Although it's not easy to find examples for that since between sensor generations usually technology and pixel count improve at the same time...
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Noise at pixel level is not the point, what matters is the visible noise when images are rescaled to the same size and output for viewing. Then the determining factors are physical sensor area (total photon collection and magnification) and the level of technological development. The old theory that smaller pixels are disproportionately less efficient is no longer true.

Image sharpness relating to sensor format is determined by lens MTF performance, that outweighs pixel considerations (within reason). Bigger is better.
 
Well I still don't agree, but I think we shouldn't split hairs here since the topic of the threat was a different one...

Edit: OK, a last word from my side. I agree that in a comparison of two resized pictures the single pixel noise doesn't matter. But how do you explain the difference between the typs of full frame sensors in the various A7 models, with the low res model A7s that enables for extremely high ISO?
 
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We are both on the same page, we just look on it differently. As I said, my initial post was misleading, what I ment (and described in the second post) is that an image of a FF sensor with let's say 36 MP (i.e. D800) and an APS-C sensor with 24 MP (i.e. D7100) one gets the same amount of noise in the detail but a higher resolution with the FF sensor. Downsizing the FF image to 24 MP, equivalent to larger pixels compared to APS-C, results in lower noise for the FF one. So in principle you are right that in the end the pixel count doesn't matter, the FF sensor collects more light which will always result in less noise, which I never disagreed in (I hope, since that would be stupid ;)).

The reason why I like to think in pixel size is that this parameter also affects other properties such as dynamic range and diffraction at aperture value, with the latter also not relevant when look on downsized images I guess...
 
madsector said:
We are both on the same page, we just look on it differently. As I said, my initial post was misleading, what I ment (and described in the second post) is that an image of a FF sensor with let's say 36 MP (i.e. D800) and an APS-C sensor with 24 MP (i.e. D7100) one gets the same amount of noise in the detail but a higher resolution with the FF sensor. Downsizing the FF image to 24 MP, equivalent to larger pixels compared to APS-C, results in lower noise for the FF one. So in principle you are right that in the end the pixel count doesn't matter, the FF sensor collects more light which will always result in less noise, which I never disagreed in (I hope, since that would be stupid ;)).

The reason why I like to think in pixel size is that this parameter also affects other properties such as dynamic range and diffraction at aperture value, with the latter also not relevant when look on downsized images I guess...
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Dynamic range and noise are basically two halves of the same coin, and not directly related to pixel size. The diffraction theory doesn't hold up in practise as it only considers resolution and ignores the much bigger impact that image contrast has on perceived sharpness (lens MTF again).

But, moving on... :)
 
You really don't like pixels, do you? Just kidding ;)
 
HoppyUK said:
Noise at pixel level is not the point, what matters is the visible noise when images are rescaled to the same size and output for viewing.
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I think it depends on use...
**many think they can crop a high MP sensor (i.e. D8xx) and keep all of the same sensor characteristics as rated for the whole frame. Or they think that they can print/display much larger with the higher resolution sensor and retain the lower noise rating/characteristic.

In other words, in comparing two cameras/sensors for producing exactly the same "equivalent" output, then pixel size doesn't really matter (above a minimum count).
But if comparing two systems in deciding what will best allow you to do something different/that you couldn't before, then pixel level performance (size) is much more relevant.

My personal preference is to compare at the pixel level...

I hate the equivalence discussion because it is very convoluted, with no clear/easy winner (IMO). I.e. Do smaller sensors require larger apertures, or do larger sensors require longer lenses? On one hand you can say the need for a shorter wider aperture lens is a detriment/loss. But longer lenses tend to be aperture limited or VERY spendy. In general, the wide/fast lens is going to be easier/cheaper, especially if you're not a f/1.x fanatic.
 
sk66 said:
I think it depends on use...
**many think they can crop a high MP sensor (i.e. D8xx) and keep all of the same sensor characteristics as rated for the whole frame. Or they think that they can print/display much larger with the higher resolution sensor and retain the lower noise rating/characteristic.

In other words, in comparing two cameras/sensors for producing exactly the same "equivalent" output, then pixel size doesn't really matter (above a minimum count).
But if comparing two systems in deciding what will best allow you to do something different/that you couldn't before, then pixel level performance (size) is much more relevant.

My personal preference is to compare at the pixel level...

I hate the equivalence discussion because it is very convoluted, with no clear/easy winner (IMO). I.e. Do smaller sensors require larger apertures, or do larger sensors require longer lenses? On one hand you can say the need for a shorter wider aperture lens is a detriment/loss. But longer lenses tend to be aperture limited or VERY spendy. In general, the wide/fast lens is going to be easier/cheaper, especially if you're not a f/1.x fanatic.
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I tend to prefer the opposite - comparisons that do take account of format equivalence, if possible. Without that, there is no context, no reference, and conclusions are therefore confused and often meaningless. Let's not call it equivalence, but simply like for like for like, side by side, on a level playing field - that's all it means.

The bit that is often missing though, is the effect that format changes have on lens performance - despite the fact that it's the single most important driver of image sharpness. In fact, it's almost always missing, possibly because it's hard to put a number on (though it can be done).
 
HoppyUK said:
The bit that is often missing though, is the effect that format changes have on lens performance - despite the fact that it's the single most important driver of image sharpness. In fact, it's almost always missing, possibly because it's hard to put a number on (though it can be done).
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One thing which can help the smaller systems with sharpness is better lenses. Recently we've seen the introduction of some very good DSLR lenses but there are still lots of lenses in use which are less than state of the art and arguably rather mediocre in comparison to the best modern ones. The more modern smaller format lenses can help to redress the balance a little here as there are some very good and relatively inexpensive ones which are good at the wider apertures and that isn't always the case with the more mediocre older DSLR lenses.
 
My simple mind thinks in terms of magnification (and it avoids talk of equivalence and crop factor altogether).

The more you magnify the more noise you get (as you magnify the noise)
The more you magnify the better the lens needs to be to give acceptable results (MTF theory or simply think you are magnifying the lens imperfections)
The more you magnify the the faster the shutter speed you need to avoid shake (as you magnify the shake)
...

And of course there are various ways of magnifying, sensor size, more MP, cropping, longer lenses, viewing at 100%, printing huge etc but ultimately if you magnify the image by whatever means then image quality will reduce.

Or conversely, the less you magnify the better the image quality; typically, in these arguments, this means a bigger sensor.
 
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Nawty said:
Or conversely, the less you magnify the better the image quality; typically, in these arguments, this means a bigger sensor.
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I tend to agree... The only caveat I would put to that is that sensor resolution does/can play a significant factor in image quality when fine detail is of concern. Of course, that requirement also puts limitations on how the sensor/lens is used, and those limitations often may not be practical.
 
HoppyUK said:
Without that, there is no context, no reference, and conclusions are therefore confused and often meaningless.
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Maybe... :)
I see the opposite as often as not (more often?)... conclusions are then extrapolated "out of context" leading to misunderstanding/erroneous assumptions.
 
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sk66 said:
I tend to agree... The only caveat I would put to that is that sensor resolution does/can play a significant factor in image quality when fine detail is of concern. Of course, that requirement also puts limitations on how the sensor/lens is used, and those limitations often may not be practical.
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And what level of fine detail is of concern depends on the magnification with which you're observing :p:D

Like I said, I have a simple mind :)
 
Nawty said:
My simple mind thinks in terms of magnification (and it avoids talk of equivalence and crop factor altogether).

The more you magnify the more noise you get (as you magnify the noise)
The more you magnify the better the lens needs to be to give acceptable results (MTF theory or simply think you are magnifying the lens imperfections)
The more you magnify the the faster the shutter speed you need to avoid shake (as you magnify the shake)
...

And of course there are various ways of magnifying, sensor size, more MP, cropping, longer lenses, viewing at 100%, printing huge etc but ultimately if you magnify the image by whatever means then image quality will reduce.

Or conversely, the less you magnify the better the image quality; typically, in these arguments, this means a bigger sensor.
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:thumbs:

Magnification is certainly at the heart of it. Equivalence is simply a term that should be fully inclusive of all factors, and puts a value on the differences :)
 
Nawty said:
Or conversely, the less you magnify the better the image quality; typically, in these arguments, this means a bigger sensor.
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Not completely true - if you can fill the sensor with the image then you need less magnification and this you can achieve with a cropped camera, assuming that your lens has the reach.

But to be quite honest in the real world it is often almost impossible to tell from a picture whether it was taken with a crop or FF camera, or taken in RAW or JPEG since many, if not most, of us no longer print at large sizes, if indeed we print at all.
.
 
petersmart said:
Not completely true - if you can fill the sensor with the image then you need less magnification and this you can achieve with a cropped camera, assuming that your lens has the reach.

.
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The point being that using a crop sensor IS magnification...
 
HoppyUK said:
(y)

Magnification is certainly at the heart of it. Equivalence is simply a term that should be fully inclusive of all factors, and puts a value on the differences :)
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Yes :)

But people have a funny habit of getting their knickers in a twist when you talk about equivalence; no idea why as it isn't exactly complicated, just fractions innit?
 
petersmart said:
We use f nos so that, regardless of the sensor size, the exposure will always be the same.
.
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Actually, t-stops will always give the same exposure whereas f-stops don't always. But if the same lens is used the difference doesn't come into it.
 
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