topic Re: Focal length EF VS EF-S in Gear Guide

Focal length EF VS EF-S

byjesper — Mon, 16 Mar 2026 11:19:13 GMT

So, perhaps I'm an idiot, but I need to get this explained.

Example A: Canon EOS 6D full frame + EF 50mm
Example B: Canon EOS 90D APS-C + EF-S 50 mm

Will these two produce exactly the same picture, or not? (I'm not thinking about lens quality or megapixels in the sensor.) Example A is the "Nifty fifty" – is example B also that (in old 35 mm film terms).

Re: Focal length EF VS EF-S

johnrmoyer — Mon, 16 Mar 2026 11:36:18 GMT

The picture will not be the same.

The APS-C camera will only use the central part of the EF lens which is usually the best part so that the same lens will be better quality on APS-C than on full frame.

Using only the center of the lens means that the angle of view will not be as wide on APS-C as on full frame. You would need to stand further away to get the same view recorded. The EF-S focal 50mm focal length is the same as the EF 50mm focal length, but since the APS-C sensor is smaller than the fullframe, the EF-S lens will be lighter weight and less expensive and the angle of view will be narrower. The full frame sensor is the same size as the 35mm film.

The photosites on the sensor will likely be closer together on the EOS 90D than on the EOS 6D. This will result in small aperture diffraction blur starting at a lower FNumber on APS-C than on full frame for the same sensor generation. In Canon DPP software or in Rawtherapee free software some of the diffaction blur can sometimes be fixed, "digital lens optimizer" in DPP or "capture sharpening" in Rawtherapee.

There are more differences.

Re: Focal length EF VS EF-S

byjesper — Mon, 16 Mar 2026 11:41:37 GMT

@johnrmoyer You noted that I used an EF-S lens in example B?

But you say Example B is still not Nifty Fifty? I would need to get an EF-S ≈32 mm lens in order to get the same picture in B as in A?

Remember, I'm only interested in how much of the scenery I will see when I'm pointing the camera forward.

Re: Focal length EF VS EF-S

johnrmoyer — Mon, 16 Mar 2026 11:46:06 GMT

@byjesper wrote:

@johnrmoyer You noted that I used an EF-S lens in example B?

But you say Example B is still not Nifty Fifty? I would need to get an EF-S ≈32 mm lens in order to get the same picture in B as in A?

Remember, I'm only interested in how much of the scenery I will see when I'm pointing the camera forward.

You are correct. The angle of view will be narrower with the same lens.
50/1.6 is approximately 32 so to stand at the same distance and get the same angle of view you would need the shorter focal length when using APS-C instead of 35mm film.

A zoom lens including that focal length would work on APS-C or a 35mm EF-S lens would be light weight.

Re: Focal length EF VS EF-S

johnrmoyer — Mon, 16 Mar 2026 11:52:24 GMT

https://www.usa.canon.com/shop/p/refurbished-ef-s-18-135mm-f-3-5-5-6-is-usm is a lens that I have and seems very high quality to me.

I also have https://www.usa.canon.com/shop/p/refurbished-ef-s-24mm-f-2-8-stm which would require cropping to get the same angle of view. It is inexpensive, very light weight, small size, and good quality.

Re: Focal length EF VS EF-S

rs-eos — Mon, 16 Mar 2026 11:54:10 GMT

Images showing this can be found in the following topic (scroll down to my reply with date of "04-29-2023 08:19 AM")

https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/Upgrading-from-My-EOS-60D/td-p/416887/highlight/true

Re: Focal length EF VS EF-S

shadowsports — Mon, 16 Mar 2026 11:58:34 GMT

Greetings,

This explains the difference between APS-C and full frame.

https://www.canon-europe.com/get-inspired/tips-and-techniques/aps-c-vs-full-frame/

It's a short read.

Re: Focal length EF VS EF-S

ebiggs1 — Mon, 16 Mar 2026 15:24:57 GMT

"Example A: Canon EOS 6D full frame + EF 50mm
Example B: Canon EOS 90D APS-C + EF-S 50 mm

Will these two produce exactly the same picture, or not?"

The simple answer is no they will not. But the top thing to remember is the FL of the 50mm lens does not change. 50mm is 50mm and will always be 50mm. The coverage of the lens to focal plane (sensor) does. The 50mm lens is still the "Nifty fifty". You see for some obscure reason somebody, a marron likely, decided people couldn't use their cameras once the smaller sensors came on the scene unless they compared it to a full frame 35mm film camera. The guys that use medium or large format cameras for instance never had this problem but somehow use crop sensor folks can't seem to manage without knowing it.

In reality every device that is capable of taking a photo has a "crop factor" even your daunted iPhone. Again, nobody cares except people that use a crop sensor digital camera. The so called terms that are related to certain FL lenses are different for different sized sensors. For instance the 50mm is considered a normal lens on a 6D. On a 90D a 35mm lens is considered to be a normal lens.

For Canon this factor is 1.6 thus, 50 x 1.6 = 80. The crop factor says the AOV will be that of a 80mm lens if you were to use it on a 90D vs a 6D.

Also in reality all cameras are FF, full frame, in the fact you get exactly what you see in the viewfinder or LCD screen. Nothing is cropped. Bottom line about all this don't worry about FL just use the lens that gives you what you want.

Re: Focal length EF VS EF-S

byjesper — Mon, 16 Mar 2026 16:19:41 GMT

So as the Holy Trinity for full-frame is 16-35 + 24-70 + 70-200 (or maybe 70-300), the equivalent in APS-C house + EFS lenses would be around 10-22 + 17-55 + 55-250? (In order to get approx the same wide angle to tele feeling.)

(I understand the Holy Trinity is also about ∫/2.8, but let's not go into that one now... 😉)

Re: Focal length EF VS EF-S

johnrmoyer — Mon, 16 Mar 2026 16:58:39 GMT

To get F/2.8 it is usually necessary to get the heavier and more expensive EF lenses instead of EF-S lenses.

Here are some EF-S lenses

https://www.usa.canon.com/shop/p/refurbished-ef-s-55-250mm-f-4-5-6-is-stm

https://www.usa.canon.com/shop/p/refurbished-ef-s-10-18mm-f-4-5-5-6-is-stm

https://www.usa.canon.com/shop/p/refurbished-ef-s-18-135mm-f-3-5-5-6-is-usm

But only this one is F/2.8 https://www.usa.canon.com/shop/p/refurbished-ef-s-17-55-f-2-8-is-usm

If you have not yet purchased the camera and do not want the cost and weight of full frame lenses, it might be good to consider https://www.usa.canon.com/shop/p/refurbished-eos-r100-rf-s18-45-is-stm-rf-s55-210-is-stm-kit or https://www.usa.canon.com/shop/p/refurbished-eos-r10-rf-s18-150mm-f3-5-6-3-is-stm-lens-kit with a kit lens or if you already have EF lenses, then the EF to RF adapter instead of kit lens.

Re: Focal length EF VS EF-S

rs-eos — Mon, 16 Mar 2026 16:59:36 GMT

Correct. That would give you the same field of view.

But as others stated earlier, focal lengths won't change and could lead to undesirable outcomes.

For example, if using around 55mm for a headshot, that will lead to facial distortions. Whereas if using something closer to 85mm, that will lead to less distortions. And when using say that 85mm with an APS-C camera, your working distance will then be further away vs an 85mm used with a full frame camera.

Re: Focal length EF VS EF-S

ebiggs1 — Tue, 17 Mar 2026 14:16:03 GMT

Bingo, you got it.

Re: Focal length EF VS EF-S

ebiggs1 — Tue, 17 Mar 2026 14:26:07 GMT

"For example, if using around 55mm for a headshot, that will lead to facial distortions."

Even this isn't totally correct or let's say complete. If you step back a few appropriate feet the result would be identical. Exactly the same. There is no inherent advantage given to a 85mm lens for portraits or any whatever FL. The real reason certain lenses became known as "portrait" lenses was studio size. Photographers were/are limited to where and how far they could stand from the subject. This is simply another reason I don't like putting "names" on certain focal length lenses. This lens is a wide angle, this lens is normal or this lens is a portrait lens, etc.

A 600mm super telephoto is a ultra wide angle lens if you are shooting the landscapes of the Moon. It all has to do with AOV and distance from subject.