topic Re: Does an EF-S lens' focal length have the 1.6 crop factor calculated? in EF & RF Lenses

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

bryannemarie — Wed, 08 Jul 2015 18:15:13 GMT

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? .

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

jazzman1 — Wed, 08 Jul 2015 18:33:25 GMT

@bryannemarie wrote:
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? .

The short answer is they would both have the same 1.6 x multiplier on all Canon Crop Sensor Body Cameras. The 1.6 x applies to the crop sensor of the camera...not the lens.

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

RobertTheFat — Wed, 08 Jul 2015 20:08:27 GMT

@jazzman1 wrote:
@bryannemarie wrote:
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? .
The short answer is they would both have the same 1.6 x multiplier on all Canon Crop Sensor Body Cameras. The 1.6 x applies to the crop sensor of the camera...not the lens.

And the long answer is that undertaking to apply the conversion factor every time you decide whether to use the lens is a fool's errand. It's far better to simply ignore the lens's behavior, if any, on a full-frame camera and learn, once and for all, how given lenses behave on a crop-frame camera. For example, a "normal" lens (i.e., one whose field of view approximates that of the human eye) has a focal length of about 31mm; a 50mm lens is a mild telephoto or portrait lens; a WA zoom would span from 10 to 20 mm approximately; etc. Once you've adopted that mindset, you need no longer concern yourself with the conversion factor and how and when to apply it.

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

ScottyP — Thu, 09 Jul 2015 09:45:47 GMT

Hi.

No.

Just like if you put, for example, an EF 50mm f/1.2 lens on a Rebel, an EF-s 18-55 zoomed to 50mm would have a field of view that appears like 80mm would on full frame. They do not give an adjusted number on the lens's stated focal length; you need to do the 1.6x multiplier on the EF-s lenses exactly as you do on an EF lens.

They do build the standard zoom lenses to different ranges though. That is why a standard full frame zoom is a 24-70 and a standard zoom for a crop camera is wider, like 18-55 or 17-55 or 17-50, etc.

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

ebiggs1 — Thu, 09 Jul 2015 14:41:28 GMT

Bob from Boston has the correct answer.

"It's far better to simply ignore the lens's behavior, if any, on a full-frame camera and learn, once and for all, how given lenses behave on a crop-frame camera."

Bottom line is a 50mm lens is a 50mm lens is a 50mm lens. It matters not that it is on a cropper, a FF or used as a telescope. It is a 50mm lens to the end.

If you must do numbers a far better one to learn is "Angle of View" (AOV). No matter what millimeter lens you use if you know the AOV, you will get exactly the same results. All lenses have this spec listed for them in their spec sheet. It should have been the way it all started but it wasn't. So here we are.

For instance you know a lens with a 84 degree AOV is a wide angle lens. Period. 46 is a normal lens. An 8 degrees and less is a telephoto. Yes, the lens millimeter measurement will be different depending on which body but the photo you make will be exactly the same.

You can easily find AOV tables to see all the ranges.

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

amfoto1 — Tue, 14 Jul 2015 18:15:36 GMT

The easiest way I've found to think of this is...

Focal length doesn't change. Period. 50mm is 50mm, no matter what format digital or film camera it's used upon.

What changes is how that 50mm "behaves" on any particular camera:

- On a "crop sensor" camera 50mm is a short telephoto.

- On a "full frame" 35mm film or digital camera, 50mm is a standard lens (not telephoto, nor wide).

- On a "medium format" film or digital camera, 50mm is a wide angle lens.

Of course, that 50mm would need to be optically designed and built a little differently for each format, in order to produce a large enough image circle to fully and evenly cover each size of film or digital sensor. In order to produce the larger image circle, the lens for a bigger image format would need to be larger and heavier, and likely more expensive. But it's still 50mm, in any case.

For example, that EF-S 18-55mm zoom set to 50mm would produce exactly the same "angle of view" as an EF 50/1.8 or EF 50/1.4 lens.

The good news is that unless you're switching back and forth between digital sensor/film formats, you really don't need to worry about it. Someone who buys and uses just one format only needs to know how the various focal lengths perform on that particular format. For example, if you buy an APS-C crop sensor Rebel T4i and that's the only camera you use, you'll soon learn and really only need to know that...

... lenses in the 8mm to 15mm range are ultrawide

... lenses from 16 to 24mm are wide to slightly wide

... lenses from 28 to 35mm are standard or normal

... lenses from 40 to 70mm are short telephoto

... lenses from 85 to 180mm are moderate telephoto

... lenses from 200mm on up are long, strong or super telephoto

And you need to know that the T4i can use any EF or EF-S lens, as well as any "crop only" or "full frame" lens for Canon made by a third party manufacturer. (If you instead bought a full frame camera such as a 6D or 5D-series model, you'd be limited to only EF/full frame capable lenses.)

Hope this helps!

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER

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

ebiggs1 — Tue, 14 Jul 2015 20:45:53 GMT

"... the lens for a bigger image format would need to be larger and heavier, and likely more expensive. But it's still 50mm, ..."

Excellent point. 50mm does not state the diameter of a lens. It is the focal ratio. Another point is no lens makes a square or rectangular image. They all produce circles. A 50mm lens that was specificly desgined for a crop type body would not look like the the 50mm f1.4 or 50mm f1.8 you commonly see.

Another reason folks should think in the terms of Angle of View. AOV does not change no matter what format it is used on.

Here is a chart.

Angle-of-view is opposite of the way manufacturers describe lenses as being 'equivalents of a such-and-such millimeter lens on a 35mm camera'. By letting go of the 35mm reference points you can start thinking of lenses in terms of their respective (and easier to reconcile) angles-of-view regardless of the optic's millimeter ranking.

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

MegLo — Fri, 08 Mar 2019 17:59:36 GMT

These answers still confused me because this did not work out the way I thought the EF-S lenses worked in terms of the focal lengths ON an APS-C camera. But now I know.

Anyway, I used my kit EF-S 18-185mm telephoto and set it to 28mm - took a picture.

Then switched to my EF 28mm prime lens - took a picture.

Both gave the same range of view.

All this time I thought the whole point of EF-S on an APS-C was that you get a full-frame effect with the 2 together as opposed to an EF lens on the APS-C where you lose more of the edges. Gonna need to do more reading...

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

kvbarkley — Fri, 08 Mar 2019 19:58:37 GMT

It depends on the *camera* not the lens. Your EF 35mm will have a different field of view on a FF camera. A 35 mm lens is always a 35 mm lens.

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

ebiggs1 — Fri, 08 Mar 2019 20:17:25 GMT

"... I used my kit EF-S 18-185mm telephoto and set it to 28mm - took a picture.

Then switched to my EF 28mm prime lens - took a picture."

28mm is 28mm no matter what lens you use. If it says 28mm it is 28mm. A lens can not change its physical characteristics once it is constructed. Crop factor is one of the most misunderstood photographic phrase. And, it is totally not needed. Medium and large format cameras and photographers do not think or even consider crop factor.

Who cares what a lens looks like on a FF camera? Especially if you don't and won't ever have one? You only care what it is and how it works on your camera. Right?

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

MegLo — Mon, 11 Mar 2019 01:47:19 GMT

I drew it out and finally understand. I wish Canon explained this differently for their lenses. All this time I was miscalculating/misjudging my lenses. I uploaded a (slightly) cleaned up version of what I sketched in the hopes that it'll help someone else.

I wish Canon would just describe it as "angle of view" or something - agree as others have noted that "crop factor" is WAY too confusing. In the beginning I guess it made sense to refer to 35mm to serious photographers. But it really wasn't clear to me (or others, it seems like) that the EF-S lenses did not adjust - I always thought the focal lengths on them referred to how it would look on a full frame camera and was doing all this calculating for my EF lenses. Now I understand why my pictures didn't always come out the way I thought they would on my EF ones. Anyway, hope this helps someone else visualize it.

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

ebiggs1 — Mon, 11 Mar 2019 14:35:14 GMT

"In the beginning I guess it made sense to refer to 35mm to serious photographers."

I was there! It never made sense. No other camera format group, I.E. medium or large etc. format are this involved and so infatuated with the crop factor or lack there of. A medium format guy typically doesn't go around thinking, lets see how does this lens 'factor' on my 35mm FF camera compared to my 120 film size camera.

I guess it must have something to do with being smaller. Because you see the P&S guys doing it, too.

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

kvbarkley — Mon, 11 Mar 2019 14:55:20 GMT

It came about because none of the original DSLR's were FF. The mfg's needed some way to inform the public that the field of view for a Non-full frame camera DSLR was not the same as the 35mm film cameras they were replacing, even though the form factor - and the lenses! - were the same. Other formats used different lens mounts, so there was no reason to make a direct comparison.

Canon complicated things even further by having both APS-C and APS-H size cameras.

So crop-factor was born. Field of View does not help, since to make it apply to every lens you would need a "Field of View factor" which would be just a different name for the crop factor.

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

ebiggs1 — Mon, 11 Mar 2019 15:30:59 GMT

""I was there! It never made sense.""

"Canon complicated things even further by having both APS-C and APS-H size cameras."

Exactly and the H sensor never fell into the crop factor concept like the C sensor did.

"Other formats used different lens mounts, so there was no reason to make a direct comparison."

They use equivalent to 35mm FF, crop factor, on P&S's even if they don't have a removable lens. It is totally unnecessary.

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

kvbarkley — Mon, 11 Mar 2019 15:53:34 GMT

APS-H had a 1.3 crop factor:

https://www.dpreview.com/forums/thread/4216745

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

kvbarkley — Mon, 11 Mar 2019 15:57:57 GMT

"They use equivalent to 35mm FF, crop factor, on P&S's even if they don't have a removable lens. It is totally unnecessary."

How else do you get a handle on a "4.5 to 18mm" lens on a '1/2.3"' sensor other than with a 35mm equivalent?

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

ebiggs1 — Mon, 11 Mar 2019 16:15:37 GMT

"APS-H had a 1.3 crop factor:"

So..........?

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

ebiggs1 — Mon, 11 Mar 2019 16:19:14 GMT

"How else do you get a handle on a "4.5 to 18mm" lens on a '1/2.3"' sensor other than with a 35mm equivalent?'

I don't! Most people that use a P&S don't care either. They don't even know what a 35mm FF camera is. They never had one and never intend on getting one. They don't care. Just another confusing number that is meaningless to them.

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

MegLo — Tue, 12 Mar 2019 00:54:51 GMT

Yeah for people like me who started off in the digital world (yes I knew what 35mm film was but I only ever used it with point-and-shoot, never tried to actually "compose" pictures as the wanna-be amateur I am now), none of that ever made sense. And yeah I'm glad kvbarkley pointed about the APS-C vs -H. WHY???? Anyway, I hope Canon reads some of these and works on a simplification.

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

kvbarkley — Tue, 12 Mar 2019 01:04:52 GMT

APS-C vs APS-H:

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