Does an EF-S lens' focal length have the 1.6 crop factor calculated?

[bryannemarie]

For example, the kits lens that is often 18-55mm purchased with a canon rebel, since it is specifically made for crop-sensored camera, is it a 'true' 18mm focal length, just as an 18mm EF lens would be on a full frame camera (other than smaller field of view)? Or to get the 18mm focal length effect, would you still need to purchase something closer to a 10mm EF or EF-S lens? In other words, say you had two 50mm lenses, one EF, one EF-S and used them on a APS-C camera (ex. Canon Rebel T4i), would they both come up with the same image or would the EF be closer to an 80mm, while the EF-S provides a 50mm image, since the lens is created with the crop factor in mind? .

[ebiggs1]

It was too expensive to jump right to full frame sensors, so Canon took the intermediate step of APS-H."

Makes you wonder how the 1Ds (first FF) ever got built?  Released less than a year after the 1D with its H sensor. As I recall the 1D was $6999 and the 1Ds was $7999 so it did cost more but not so much as a percentage of the total coat.

[kvbarkley]

They might have learned how to improve the yield with the APS-H so much that it was only a $1000 adder for the Full frame.

The area increased 67% from APS-C to APS-H and another 58% from APS-H to FF- so not quite as big a jump. They might also have caught a lucky break with an increase of wafer size. Silicon wafers have increased in size from about 4" to 12". With each step, you have to change all the tools in the fab to handle the new size. With a larger wafer, even if the yield (defects/mm^2) stays the same, you get a lot more sensors so you are likely to get more per wafer.

[kre84u]

I've read this entire, years-long thread, and I don't see a clear answer to the OP's question. Let's say I own two lenses: an EF 24-70 and an EF 70-200. Yes, a lens is a lens; a focal length is a focal length. But, these two lenses will both be cropped on an APS-C, and they will, as a result, have an "effective focal length" greater than stated on the barrels, because the sensors capture only a portion of their image circles and the smaller sensor's image is enlarged to output dimensions equivalent to that of a FF sensor.

However you want to describe it, the coverage of these two lenses will be seemless, as follows:

EF lenses with 24-70 and 70-200 will yield effective 38.5mm - 112mm and 112mm - 320mm

But, if you substitute an EF-S 24-70, the question now becomes, does the effective focal length of the shorter lens change from what you got with the EF version? Does it yield an effective 38.5mm - 112mm, or does it yield an effective length of 24mm - 70mm?

The question matters if you want seemless coverage of focal lengths across two zoom lenses on the same camera body, i.e., no gap in zoom range for your captured images.

[kvbarkley]

A 24-70 will have the same field of view no matter whether it is EF or EF-S. The visible field of view will be narrower on an APS-C sensored camera.

[kre84u]

So, I take your response to mean that the images, taken at the stated length of 70mm, for both the EF and EF-S lenses, will be indistinguishable. That the EF-S, despite not throwing away any image circle, will have its image "cropped" as much as the EF. Makes no sense to me.

[kvbarkley]

On an optical bench they are indistinguishable. In a real camera, there is a difference.

The FF camera will have a field of view of 35 degrees

The APS-C camera will have a fov of 22 degrees.

A 70 mm EF-S lens does indeed "throw away" image circle. What makes you think it doesn't?

[kvbarkley]

Just to add to my own reply:

The new Fuji MF camera would have a 46 degree FOV with a 70 mm lens. So if you compared this camera with an EF FF camera you could also say that the 70 mm lens on a FF camera "throws away" image circle compared to MF.

[kre84u]

"Canon EF-S lenses have a smaller image circle that is only big enough to cover the smaller sensor found on Canon APS-C cameras."

If this is true, then there is nothing being thrown away, in the sense that a smaller sensor would throw away a portion of the EF lens's image circle.

[kvbarkley]

Size of the image circle has to do with other things besides "classic" lens design.

For example, you can use an EF-S lens on a Canon R, but it restricts the image to the size of an APS-Sensor. You probably have "image" out there, but Canon cannot guarantee the quality. I imagine the field curvature goes out of whack, among other things.

[ebiggs1]

"If this is true, then there is nothing being thrown away,..."

"It was about EF-S vs EF lenses with the same focal length dialed in and on the same APS-C camera, identically placed, seeing the exact same subject. Are the resulting images different?"

This topic which isn't difficult to understand.  It has been made difficult by some folks in the beginning seeing a difference in their photos from what they saw with 35mm film.  This whole crop factor myth is a joke and totally necessary. Medium format  and large format guys don't use it although they have it.

Let's get out of the "weeds".  A lens FL is what it is when it is manufactured.  It never changes nor can it change.  If the lens is a 70mm ef-s or a 70mm ef or a Hasselblad 70mm lens, it is a 70mm lens no matter what camera it bolts on to. The printing on the lens body is what the lens physically is.  The AOV  (angle of view) will be different but not the FL. Second, and probably the most difficult concept to get over is nothing is cropped. Nothing is thrown away. If you believe that, something must added when you go up in sensor size, if something is throw away as you go down. I am sure the larger sensor doesn't create it out of the air.

Another confusing part or at least what most people don't know is just what is a lens? They think a lens is that black tube with rings and glass and markings on it. Actually a lens is a piece of glass with curved sides for either concentrating or dispersing light rays.   WHat is FL, for camera lenses the distance between the center of a lens and its focus point. It is not a measurement of the actual length of a lens. FL tells us the AOV (angle of view). The longer the FL, the narrower the AOV will be, higher magnification. And of course, the shorter the FL, the wider the AOV will be.  This is where the "equivalent FL" or "crop factor" got its beginning. People were talked into using a crop factor, 1.6x, in favor of just learning the AOV a lot less confusing.

Hopefully this has clearned it up a bit.