Crop Factor. Something to consider when buying a lens when you are shooting other than FF.

Started Jun 6, 2014 | Discussions thread
Febs Contributing Member • Posts: 512
Re: What about medium format or larger?

JackM wrote:

Febs wrote:

Jack, you make the assumption to use the same lens (or at least the same aperture) in comparing different formats. Leave that assumption away for a moment and you will understand what the others meant.

So for example look at a camera system with a 24Mpix FF sensor and 50mm f2.8 lens and then compare it to another camera system with a 24Mpix APSc sensor and 35mm f2.0 lens.

These 2 systems are equivalent in practically every regard:

  • Field of view
  • Depth of field
  • Noise (the larger aperture compensates for the smaller sensor)
  • Resolution
  • Size
  • Price (with a slight advantage to the APSc system)

Hence it doesn't matter which system you pick. In the real world choose any system that has the lenses which cover your need.

I didn't say anything that disagreed with you.

No sensor size has an intrinsic advantage over another.

Well, in Canon land, they do. I had a 7D and a 5D2 at the same time. I did every test every which way, there was no way to make the 7D look as good as the 5D2. At low ISO it was a barely significant difference, but it was there.

True, the Canon FF system is ultimately more powerful. That's because there are no equivalent lenses in the APS-c range that match the 50mm 1.4 (would be a EF-S 35 f1.0), 100mm 2.0 (would be an EF-S 70mm 1.4) etc. The 2 systems are engineered to coexist, each with specific advantages.

Now if you were only interested in a large aperture standard zoom for your camera, you could pick the 7D + 18-35 f1.8 just as well as the 5D II + 24-70 f2.8 and there would be no noise advantage to either.

That being said I conclude again, sensor size doesn't matter. It's the light gathering power of the lenses available for a particular brand & sensor size that either fit your bill or don't.

 Febs's gear list:Febs's gear list
Kodak DCS Pro SLR/n Sony Alpha a99 Sony 50mm F1.4 Sony 16-35mm F2.8 ZA SSM Carl Zeiss Vario-Sonnar T* Sony 70-400mm F4-5.6 G SSM +5 more
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