Does a RF-S lens focal length take the crop factor into account?

[aedcce]

Right now, for the EOS R cameras, there are RF and RF-S lenses.

If I were to get the RF 16mm for my R10, for example, the 1.6 crop factor would make it more equivalent to a 25mm focal length.

The RF-S lenses, however, are specifically designed for crop sensor cameras. Would I still add this multiplier or is the number the same as on the box for RF-S lenses?

[kvbarkley]

I would describe it by what it is:

                        FF                   APS-C

wide angle     less than 20      less than 15

moderately wide angle 20-30     15-20

normal                        30 - 70      20 - 40

short telephoto           70 - 90        40 - 60

telephoto                    > 90              >60

[wq9nsc]

As others stated, lens focal length is a function of the lens design so it doesn't vary by the camera on which it is used.  But the results do and that is why I think in terms of "equivalent focal length" when using an APS-C size sensor like my little M6 M2 uses.

For decades, the most common pro or semi-pro cameras used 35mm film and digital cameras that use what is commonly called a full size or full frame sensor have a sensor size nearly identical to a 35mm film camera.  For those of us who used film for years and then full frame digital, we are used to thinking in terms of specific focal length when choosing a lens application or when considering the minimum shutter speed to reasonably avoid blur from camera shake.  For those of us who have those numbers "baked" into our brain, it is useful to use the 1.6x focal length multiplier when using an APS-C sensor so that we can make decisions based upon numbers we have a lot of experience using.

My first "real" digital was a Canon 1D Mark II which used a APS-H sensor with a 1.3X "crop" factor, close enough that I thought in terms of conversion but in reality it wasn't far enough off from full frame to make much difference.

Rodger

[normadel]

I care because I like a clear, simple explanations for things, when there is one. Many folks have to dive deep into subjects here when questioners sound like they'd benefit from the KISS principle.

[Tronhard]

I too prefer an explanation: so in the best traditions of the KISS method:  🤔

In response to the OP's question:
"Would I still add this multiplier or is the number the same as on the box for RF-S lenses?" 
The focal lengths of lenses are a physical constant, so if one is considering a RF 50mm lens and a RF-S 50mm lens, they are both multiplied by the crop factor if one wants to know what the equivalent lens would be on a FF body to get the same Field of View.

[normadel]

Sorry, Tronhard. I don't see how your explanation says any more than mine did.

Oh well......

[Tronhard]

Actually, I was not specifically targeting your post, simply stating my own position. 

I gave a much more detailed explanation below, which I stick with, and I like to produce reference material to underpin that.  However, since you seemed to want the short version:"

questioners sound like they'd benefit from the KISS principle."  I gave that too - but specifically targeted at the OP's precise question - I hope!

The facts are well established, the rest comes down to how those facts are presented and I see no reason for debate over that.  The main thing is the OP understands what is happening here.

[Tronhard]

questioners sound like they'd benefit from the KISS principle."  I gave that too - but specifically targeted at the OP's precise question - I hope!

The facts are well established, the rest comes down to how those facts are presented and I see no reason for debate over that.  The main thing is the OP understands what is happening here.

[ebiggs1]

"So how would YOU describe/label what happens when putting a lens on an APS-C body?"

I wouldn't. The lens used on any camera is just the lens used on any camera. Medium format guys don't think crop factor and neither should APS-C folks. A 28mm lens., etc., does what it does on each format and there's the end to it. It's a 28mm lens, period.

[ebiggs1]

"Why do you care? It has the field of view it has. There is no reason to make 35mm some standard of reference, especially if you have never used a FF camera."

Gold star answer.

[ebiggs1]

"For decades, the most common pro or semi-pro cameras used 35mm film and digital cameras that use what is commonly called a full size or full frame sensor have a sensor size nearly identical to a 35mm film camera.'

Probably true for mobile users but certainly not for studio use. We never used 35mm cameras at work only when we were out on a mobile assignment. I never heard anyone say, I wonder what the equivalent FL of this lens is on my medium format camera or my 8x10 box camera. It was a term that wasn't needed and has caused so much confusion because of it.

[ebiggs1]

"Smaller sensors like APS-C will have a narrower angle of view than a camera with a larger sensor with the same focal length lens"

I wouldn't say that isn't true but it isn't complete either. It does depend how big the sensor is but not all sensors stop at the 35mm FF size. The crop equivalent goes the other way as sensors get larger than 35mm size. And in that group nobody cares!