Convert EF-S lens on an APS-C Camera (60D)?

[Justin]

Do you have to convert an EF-S lens on a cropped sensor camera (60D)? I have searched the forum and not gotten a very clear answer.

I am looking at 2 lenses: EF 28mm f/1.8 USM and EF-S 24mm f2.8 STM

At first glance they look very similar: only 4mm difference between them. However, since I am shooting with a Canon 60D and it is a crop sensor, then I assume that I must multiply the lens by 1.6 to get the correct size. So 28mm would be 44.8mm on my camera. Since the 24mm lens is an EF-S lens then would it still be 24mm on my camera with no conversion necessary? Or do I still have to convert it to 35.2mm?

Justin

[kvbarkley]

They always report the correct focal length, so you can directly compare EF and EF-S focal lengths.

[RobertTheFat]

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@Justin wrote:

Do you have to convert an EF-S lens on a cropped sensor camera (60D)? I have searched the forum and not gotten a very clear answer.

I am looking at 2 lenses: EF 28mm f/1.8 USM and EF-S 24mm f2.8 STM

At first glance they look very similar: only 4mm difference between them. However, since I am shooting with a Canon 60D and it is a crop sensor, then I assume that I must multiply the lens by 1.6 to get the correct size. So 28mm would be 44.8mm on my camera. Since the 24mm lens is an EF-S lens then would it still be 24mm on my camera with no conversion necessary? Or do I still have to convert it to 35.2mm?

Justin

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If you use only a "cropped" sensor camera or only a full-frame camera, you can ignore the conversion factor. Just learn what to expect of a lens with a given focal range on the camera you're using.

The conversion factor becomes useful when you're using two cameras (as many event photographers do), one of them cropped and the other FF, but only to ensure that you're not leaving an unwanted gap between the coverages of the two cameras.

[Tronhard]

First the EF lenses are designed originally for a full frame camera, but they can be used on an APS-C body.  EF-S lenses cannot - basically the smaller mirror of the APS-C body means that the EF-S lens can protrude further into the camera body - this allows the EF-S lens to be made much more cheaply without necessarily losing quality.  There is a misconception that EF-S lenses are somehow inferior, while in fact the glass is in the better ones is the same quality as the EF and even L lenses.

So to considering the focal length numbers...  First the physical functions of an EF lens will not be altered by placing it in a APS-C body, however what the sensor "sees" i.e. its Field of View has an impact.  It is this difference in image size and how the lens "sees" that is considered when we talk about Equivalence.

I recommend this article: https://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care

Also these videos on Youtube: 

Northrop:  https://www.youtube.com/watch?v=f5zN6NVx-hY

ImageIQ:  https://www.youtube.com/watch?v=lte9pa3RtUk       Equivalency is discussed around 10:55 into the video

So if you get the gist, lenses are always identified with focal lengths in terms of a Full Frame body, but since you are using an APS-C body you must multiply ANY lens by the crop factor (1.6) to get the Equivalent Focal Length or Field of View  So even though your EF-S says it is 24mm Focal length, it will behave or see like a 24 x1.6=38mm lens and the 28mm EF lens will behave and see like a 28x1.6= 45mm focal length lens.

As was correctly mentioned above there is not much difference between these two lenses in terms of their relative performance, the question is did you want a lens that actually performs with a FoV of around 24mm?  If you DO, then you want a lens with a focal length of 24/1.6 = 15mm (as you read it on the barrel of the lens) or something in the range of 15-17mm.  Doesn't matter if it is EF or EF-S.

[kvbarkley]

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@Tronhard wrote:

So if you get the gist, lenses are always identified with focal lengths in terms of a Full Frame body, 

No, the focal length is reported as the actual focal length of the lens, it has nothing to do with the format.

[Tronhard]

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@kvbarkley wrote:

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@Tronhard wrote:

So if you get the gist, lenses are always identified with focal lengths in terms of a Full Frame body, 

No, the focal length is reported as the actual focal length of the lens, it has nothing to do with the format.

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If you read my post carefully, you will see that I tried to say that the Physical properties of the lens remain constant (frankly to suggest anything else is absurd), thus its physical focal length remains the same, however it's Field of View makes it BEHAVE as if its focal length is longer - I clearly said that is was not the physical properties of the lens, but what it "SEES"  or delivers to the sensor - that is the whole point of  Equivalence!  And it's how the lens BEHAVES that is the most important.  I am backed up by the articles and videos I posted.

As far as the comment that lenses have their focal lenght described in terms of a FF 35mm format I enclose a screen shot of the Canon USA website indicating the focal length range of the Canon Powershot SX60HS.  It clearly indicates that the zoom range is 21-1365mm - which is not its PHYSICAL focal length range but its EQUIVALENT FL range (although this is not identified in the page) - the physical FL range is in fact 3.8 - 241mm.

DPReview at least mention that in their description of the same camera:

"The PowerShot SX60 HS has a gigantic 65X optical zoom lens. equivalent to 21-1365mm (naturally, it has image stabilization)"  (I emphasized the word in case you missed it...)

The point being that the numbers camera manufacturers put on their lenses are intended to give a value equivalent to that of a 35mm camera format.  BUT if the camers is NOT a 35mm format (as in the case of APS-C) then to get the same comparison of what the lens will deliver to the sensor one should apply the equivalence factor.   Absolutely the physical properties of the lens have not changed, but significantly what the sensor has delivered to it does.

The article and videos speak for themselves.

the OP wanted to know if he should multiply only the EF-S lens FL value and not the EF value.  I hope we can all agree that if he wants to get a true comparison between ANY EF-S lens and EF lens he must apply the same factor.   My question was still valied... Did he want to actually have a certain FL delivered to his sensor, then he must consider the crop factor in that,

[kvbarkley]

That is the marketing hype.

The specs say:

And I bet this is printed on the lens, too.

Again, the angle of view of a 50mm EF-S lens on an APS-C camera (if there was such a thing)is the same as the angle of view of an EF 50 mm lens on an APS-C camera.

[Justin]

Thanks for the info. I wondered why Canon would list the field of view for a full frame camera on a EF-S lens that can not fit on a full frame camera. This makes no sense at first, but after reading all of the replys, and watching the videos, it makes sense to have a standard unit of measurement for lenses, which is the full frame camera.

I was not aware of the conversion factor years ago when I bought my 50mm lens and was disappointed with its angle of view. It was like a telephoto lens and I couldn't fit anything in the viewfinder.

Now I am shopping for a small low light lens to use indoors in more of a close-up situation. So it appears that I am dealing with a 38.4mm (the EF-S 24mm f2.8 STM lens) or a 44.8mm (the EF 28mm f/1.8 USM lens). Any comments/reviews on these lenses are welcome. I have heard good and bad things about the 28mm f/1.8 USM lens.

[ebiggs1]

"...it makes sense to have a standard unit of measurement for lenses, which is the full frame camera."

The lens FL has nothing to do with a FF camera.  The lens is what it is. It relates to nothing but itself.  People are what confused to matter.

[ebiggs1]

Robert is correct with his statement, "Just learn what to expect of a lens with a given focal range on the camera you're using."

The FL of a lens can not change unless something mechanical happens to it.  It matters not what camera you mount it on.

A 50mm lens is a 50mm lens is a 50mm lens. It matters not what name you put on it.  The AOV ( angle of view) is what changes.  The smaller sensor sees less AOV than a larger sensor.  Example if you put the same lens on a larger medium format camera the conversion factor would be negative IE less than 1 to 1. 645 medium format crop factor is 0.62.

A 28mm lens has a 74 degree AOV on a FF camera. If you want a WA lens that has a 74 degree AOV for your 60D, you would select a 18mm lens. As you might conclude as the sensor gets even smaller, a P&S for example, WA lenses are no longer possible or at least none exist.

And, when you go towards the tele side of the deal, you can get into some serious FL when using a cropper. That is why some folks love them for wildlife work. There is an old saying with us old photographers, "You can never have too much FL."