help me understand lens multiplication please

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Clouds

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HI

I am looking at APS mirrorless cameras, the sony a6700 and canon R7

The sony has a crop factor of 1.5 and the canon 1.6 - am okay so far

so taking the canon , I will use the two lens below to help me pose the question

RF 100-400 f5.6-8IS USM which is listed as a full frame lens
RF 18-150 which is listed as a APS lens

so my question is regarding the x crop factor difference between full frame and APS lens

so if we take the canon 1.6 crop factor camera

  1. the 100-400 is full frame so do I multiply by the 1.6 making it 160- 640
  2. because the 18-150 is a APS lens do you still need to times 1.6 ? making it 28-240 or is it just a 18-150 because its APS camera and lens

if you only x 1.6 the full frame but not the APS lens and if not , that you have to 1.6 both full frame and APS lens , why have the two types

thanks for reading


​

 
Last edited:
You may wish to try this site and see if that answers your questions...

www.omnicalculator.com

Crop Factor Calculator

The crop factor calculator tells you the effective focal length and aperture f-stop of your camera in terms of standard 35mm lenses.
www.omnicalculator.com www.omnicalculator.com
 
Clouds said:
that you have to 1.6 both full frame and APS lens , why have the two types
Click to expand...
Purely for the lens mount. Some crop lenses had rear elements that meant they would be hit by a mirror in a FF camera, the different lens Mount ensured this didn’t happen.

But for absolute clarity; focal length is a physical attribute (can be physically measured within the lens). We use equivalence and crop factors as a short hand for what we expect to ‘see’, which isn’t focal length at all, but angle of view.
 
Clouds said:
HI

I am looking at APS mirrorless cameras, the sony a6700 and canon R7

The sony has a crop factor of 1.5 and the canon 1.6 - am okay so far

so taking the canon , I will use the two lens below to help me pose the question

RF 100-400 f5.6-8IS USM which is listed as a full frame lens
RF 18-150 which is listed as a APS lens

so my question is regarding the x crop factor difference between full frame and APS lens

so if we take the canon 1.6 crop factor camera

  1. the 100-400 is full frame so do I multiply by the 1.6 making it 160- 640
  2. because the 18-150 is a APS lens do you still need to times 1.6 ? making it 28-240 or is it just a 18-150 because its APS camera and lens

if you only x 1.6 the full frame but not the APS lens and if not , that you have to 1.6 both full frame and APS lens , why have the two types

thanks for reading


​

Click to expand...

The RF-S 18-150 lens is specifically designed to be used with crop sensor cameras such as the R7. If you were to put that lens on a full frame camera such as the R5 it would automatically crop the image. And yes you still have to multiply the focal length by 1.6.
 
You buy your first lens and before long you have another then what do you know you have 4 and so it goes on. ;)
 
Clouds said:
...

if you only x 1.6 the full frame but not the APS lens and if not , that you have to 1.6 both full frame and APS lens , why have the two types

...

​

Click to expand...
I addition to what @Phil V wrote, a lens designed for an APS-C camera only has to project an image large enough to cover the smaller APS-C sensor - allowing the APS-C lens to be physically smaller and lighter, and so cheaper.
 
Crop factor is simply one of many forms of magnification... it is the fact that a smaller sensor area has to be enlarged (magnified) more in order to generate the same sized output; so the lens' effective FL is increased (magnified).

It is literally *exactly the same as cropping in post... but no-one ever accounts for that; you really should...


(*assuming equivalent pixel densities)
 
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