Crop Factor - any effect

MatBin

MatBin

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matt
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Does crop factor really matter, when we use say a 300mm lens on a FF, 1.3 or 1.6 we get exactly the same image/magnification (or lack of) on the film plane/sensor, so when people write that 'crops' are better because of more reach I am somewhat sceptical, all you get surely is less of the whole image on the sensor on a crop format (hence the name).
Surely you can get exactly the same actual printable image by 'cropping' the results from a FF/1.3 image to match the image from a 1.6 jobby- you may not get as many pixels in the result (depending on where you start from of course), so I dont see (no pun) how a crop sensor will actually be of any significant benefit unless you have more Mp in the final image via the crop sensor.
A 5Dmk2 with 21Mp must surely give a better 'cropped' image than say a full 20D image?

Matt
 
I think it's to do with final image. I believe someone has worked out that if you crop an image from a 21mp 5D2 so that it represents the same field of view as would have been captured by a crop camera using the same lens, you actually end up with less pixels on target compared to the crop camera image.
 
If you crop a 5D2 down to 1.6x format, you get 8mp which is similar to a 40D's 10mp. So it's kind of two cameras in one in that sense.

On the other hand, the contemporary equivalent is the 7D with 18mp. It also runs at 8fps, has a better AF and metering system, and costs a lot less.
 
Which equates to better light gathering power, which is why FF or FX is better in low light, but it doesn't mean it will produce a cropped image that will hold equivalent detail to the shot taken with the same lens on a crop sensor.

I used to have a 10" light bucket (dobsonian telescope) great for light gathering power and it sure pulled faint objects out of the gloom, but when looking at a bright target my old 60mm APO refractor beat it as it had better contrast, giving a crisper view.
 
iancandler said:
Which equates to better light gathering power, which is why FF or FX is better in low light, but it doesn't mean it will produce a cropped image that will hold equivalent detail to the shot taken with the same lens on a crop sensor.

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Yes it does.

A good comparison is the crop format Nikon D300 against the full frame D700, with the same lens. Same number of pixels on each sensor. The D700 absolutely thrashes it every which way.

That's not to say that the D300 isn't very good indeed, because it obviously is and plenty good enough for most people - hence the overwhelming popularity of croppers. But when you push the output size and are wanting to retain excellent sharpness, push the the ISO, and go looking for that last drop of dynamic range, the full frame D700 wins every time.

The sensor is just collecting more than twice as much light (photons) and the lens is having to work half as hard to deliver the same level of detail.

A similar comparison is the Canon 7D vs 5D2.

PS Pixel density (per sq mm) and pixel size should not be confused!
 
testbloke said:
That is a good point, but the latest crop sensors pixel density is not far from full frame
Click to expand...


Pixel density on a FF is a lot less than a crop sensor due to the massive size difference, the 7D has over twice the pixel density per sq cm than that of a 5D2.
 
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