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]

Focal length is focal length, a physical characteristic of the lens. The focal length listed is the actual focal length.

Have you ever owned a full frame camera? The *only* reason to care about crop factor is that you are used to 35mm fields of view.

[deebatman316]

All an APS-C lens does is provide an image circle large enough. To cover an APS-C image sensor size. The image sensor is what causes the crop. Not the lenses so there is always a 1.6x crop factor. Regardless of what lens you use on it. All lenses use 35mm focal lengths. They don't factor in the 1.6x crop factor. 

[kvbarkley]

"All lenses use 35mm focal lengths"

All lenses use focal lengths. 35mm has nothing to do with it.

[ebiggs1]

""All lenses use 35mm focal lengths"

All lenses use focal lengths. 35mm has nothing to do with it."

This is how the confusion gets started and how it is kept going. A lens is a lens is a lens and will always be. The camera it is attached to is irrelevant. Crop factor is a meaningless term that should have never been coined.

[p4pictures]

As others have said the focal length of the lens is a character of the lens. A 50mm lens used on a full-frame EOS camera is still a 50mm lens when fitted to an APS-C camera.

The confusion has come around since the focal length was used as a way to express the angle of view provided by a lens. The angle of view depends on the focal length AND sensor size. 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.

As an example the RF 50mm F1.8 STM lens spec sheet lists the following:

Angle of View (Horizontal, vertical, diagonal) - 40°00′, 27°30′, 46°00′

For most photographers the angle of view is even more complex to remember and understand than a single focal length number. This is what the focal length is used.

The effect of the smaller APS-C size sensor is to reduce that angle of view, but rather than give the figures, a neat workaround is to use a crop factor or multiplier to try and make sense of the narrower angle of view. For an APS-C size sensor the crop factor is 1.6x. Meaning the 50mm lens on and APS-C camera will have an angle of view similar to an 80mm lens on full-frame camera.

Taking the RF-S 18-150mm kit lens as an example, the camera shows the actual focal length on the screen as you zoom from 18-150mm, however the angle of view captured is more like a 28.8 to 240mm lens would be on full-frame camera.

[normadel]

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

An APS-C sensor/body IS cropping what the lens takes in, showing what a full-frame sensor would see on a full-frame camera. The crop factor tells you the "equivalent". What's the problem?

[kvbarkley]

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.

[kvbarkley]

Actually the specs are in error. They do not say that the AOV is specified for a full frame camera.

[Tronhard]

Hi and welcome to the forum:
As you can see this is a subject fraught with challenges!  I would offer the following article I wrote on the subject that is based on physics, material from a professor in photographic optics, and has been peer reviewed.
Focal Length, Sensor Size, Equivalence and Field of View 

I will simply say, for the discussion, that a lens' focal length is a physical characteristic of a lens.  It does not change, whatever type sensor is behind it, from what is written on the lens.  However, what the sensor captures does impact the final result.  This result is the called Field of View (or Field of Capture) and should always be identified as such.  The image area recorded by a smaller sensor will be smaller: however, when magnified in a screen or print to the same area or to a common size (e.g. both formats printed in an 8"x10" format), will seem to render a result similar to using a longer focal length lens.  The magnification is not done in the lens.
The top shows what is captured, the bottom shows the result after magnification of the image later

In an effort to encompass this phenomena, and explain it in terms of the lens alone, writers and reviewers have coined the term 'crop factor', and applied it to the focal length, but actually it is applied to the Field of View, and this is where the confusion begins.  The lens is not 'cropping' the image, the sensor is.  Arguably, Ernie is quite correct in saying that all images are cropped, because the image projected by the lens is actually circular - as they were in the early Kodak box cameras:
Images from and early Kodak Box camera (ref. Kodak.com)

However, the vernacular term 'Full Frame' came about as the 35mm format became a de facto standard in the mid- to- latter part of the last century - basically for its combination of decent imagery, combined with the smaller, lighter cameras and high-quality lenses that could use it.  Certainly that dominance was driven home by the proliferation of the 35mm SLR camera.  Smaller size films (and later sensors) thus became known as 'cropped'. 

To put it another way, in the context of your question: "Would I still add this multiplier or is the number the same as on the box for RF-S lenses?"  If using an APS-C camera, you multiply the focal length of ANY lens by the crop factor (RF or RF-S) to compare it to the focal length, if using a FF camera, to achieve the same Field of View .  So, a 50mm lens (be it an RF or RF-S lens type) will create a FoV equivalent to an 80mm lens on FF camera.  Conversely, if you want to put a lens on your crop-sensor camera that will yield the same "normal" FoV as a 50mm lens on a FF camera, you divide the required value by the crop factor.  Thus, to get the same FoV, 50mm/1.6 = 32mm to get a 'normal' FoV.

The name APS-C (Advanced Photo System type-C) actually comes from a move by a consortium of film makers in 1996. For a full explanation of the the format see Advanced Photo System - Wikipedia.  The format was essentially overtaken by the rise of the digital camera, and so died out pretty quickly, but was reborn as a digital sensor format.