Focal length EF VS EF-S

[byjesper]

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).

[johnrmoyer]

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.

[byjesper]

@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.

[johnrmoyer]

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@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.

[johnrmoyer]

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.

[rs-eos]

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...

[shadowsports]

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.

[ebiggs1 · Accepted solution]

"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.

[byjesper]

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... 😉)

[johnrmoyer]

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.