I'm sorry if it seemed like I was accusing you of something or if I formulated my post to confusingly. I just wanted to present my understanding of the reach advantage of higher pixel density bodies so that somebody could point out a flaw in it if it exists.
Things like the formula for spatial resolution that was mentioned in another threat here just don't come up in the kind of YouTube Videos I watch, for example.
And you are right that theory has its limits, but it also has its value. For example, I used to believe that the act of raising the ISO itself is the source of noise that appears when working with low light, until I read into Signal to Noise ratio.
A FF und m4/3 Body stand in the same Position an have the same 300mm 4.0 lens attached. The FF body will have a wider FoV. To match the crop Bodies FoV there are three options:
- Crop the image in half horizontally and vertically. By doing this, 75% of the gathered signal and resolution is discarded, raising the Signal to Noise Ratio to the same value as the Crop body (Assuming similar sensor technology) .
- Use a 2X Teleconverter. By doing this, the Signal is also reduced by 75%. The sensor resolution is maintained though. Total resolution will still be affected by the quality degradation in the lens + TC system.
- Use a lens with 600mm focal length. If the current aperture is to be maintained to maintain the amount of Signal this requires the purchase of the 600mm 4.0.
Obviously the first option has no additional weight or cost. Once cropped to the same FoV, the images from both cameras should be equal if their pixel density is equal. Otherwise, the body with higher density (Which today would most likely be the crop body) should have the advantage when the output size is big enough to show the difference in detail.
The second option is the same, except now no cropping is involved and total amount of pixels can be compared instead of pixel density. Oh, and it adds a bit of weight and cost to the FF system.
The third is optically the best, as no signal and no resolution are lost for the FF System, giving it a 2 stop advantage over the crop system in terms of gathered signal. However, the price increase will rule this option out for many.
Does that make it clearer what I was trying to say? I'm not Considering the 300mm or 600mm as lenses to buy, I just used them to make the point that the term reach advantage could be meaningfull.
I only brought up the sigma zoom to show why I'm curious about the subject. But lets ignore that, I'm really just curious about the theory. It's what I find the most interesting about the CR forum.
Things like the formula for spatial resolution that was mentioned in another threat here just don't come up in the kind of YouTube Videos I watch, for example.
And you are right that theory has its limits, but it also has its value. For example, I used to believe that the act of raising the ISO itself is the source of noise that appears when working with low light, until I read into Signal to Noise ratio.
Let me try to put my example differently:
A FF und m4/3 Body stand in the same Position an have the same 300mm 4.0 lens attached. The FF body will have a wider FoV. To match the crop Bodies FoV there are three options:
- Crop the image in half horizontally and vertically. By doing this, 75% of the gathered signal and resolution is discarded, raising the Signal to Noise Ratio to the same value as the Crop body (Assuming similar sensor technology) .
- Use a 2X Teleconverter. By doing this, the Signal is also reduced by 75%. The sensor resolution is maintained though. Total resolution will still be affected by the quality degradation in the lens + TC system.
- Use a lens with 600mm focal length. If the current aperture is to be maintained to maintain the amount of Signal this requires the purchase of the 600mm 4.0.
Obviously the first option has no additional weight or cost. Once cropped to the same FoV, the images from both cameras should be equal if their pixel density is equal. Otherwise, the body with higher density (Which today would most likely be the crop body) should have the advantage when the output size is big enough to show the difference in detail.
The second option is the same, except now no cropping is involved and total amount of pixels can be compared instead of pixel density. Oh, and it adds a bit of weight and cost to the FF system.
The third is optically the best, as no signal and no resolution are lost for the FF System, giving it a 2 stop advantage over the crop system in terms of gathered signal. However, the price increase will rule this option out for many.
Does that make it clearer what I was trying to say? I'm not Considering the 300mm or 600mm as lenses to buy, I just used them to make the point that the term reach advantage could be meaningfull.
In your example you compared a 30mm lens on the m4/3 body to a 60mm on the FF body. I understand that as "To match the FoV between bodies of different sensor size, use greater Focal lengths on the body with the greater sensor size". So I used an example where this is more or less impossible due to price constraints to show how the term reach advantage could make sense.
Okay, I wrote noise in the last post when I should have used signal to noise ratio. Which should be the same as what you call low light Performance.
Sensor size makes a difference. A larger sensor captures more signal if all other factors (Exposure time, f-number, lightsource) are equal. However, this signal gets reduced when you crop, so the output of a larger sensor should become equal to the one from a smaller sensor if cropped to the samw size. At that point, given similar sensor tecchnologies only the remaining resolution should determine image quality. Am I wrong?
I think all dak723 said that to match a 20MP m4/3 sensor's pixel density you would need an 80MP Full Frame sensor. Which is true. Obviously the Full Frame sensor is now equal or better than the smaller sensor in any situation in terms of image quality.
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