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? .

[jazzman1]

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@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? .

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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.

[RobertTheFat]

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@jazzman1 wrote:

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@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? .

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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.

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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.

[ScottyP]

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.

[ebiggs1]

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.

[amfoto1]

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 

[ebiggs1]

"...  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.

[MegLo]

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...

[kvbarkley]

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.

[ebiggs1]

"... 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?