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Frequent Contributor
Posts: 33
Registered: ‎12-29-2012

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

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

Esteemed Contributor
Posts: 3,466
Registered: ‎02-17-2016

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

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

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Posts: 5,040
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Re: Convert EF-S lens on an APS-C Camera (60D)?


@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


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.

Bob
Philadelphia, Pennsylvania USA
Reputable Contributor
Posts: 543
Registered: ‎10-18-2016

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

[ Edited ]

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.

"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
"I have never been able to enlarge a photograph... I am just interested in the shots" Henri Cartier-Bresson
Esteemed Contributor
Posts: 3,466
Registered: ‎02-17-2016

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


@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.

VIP
Posts: 11,491
Registered: ‎12-07-2012

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

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."

EOS 1DX and 1D Mk IV and several lenses!
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Posts: 543
Registered: ‎10-18-2016

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

[ Edited ]

@kvbarkley wrote:

@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.


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.

 

SX60HS zoom range.jpg

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,

"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
"I have never been able to enlarge a photograph... I am just interested in the shots" Henri Cartier-Bresson
Esteemed Contributor
Posts: 3,466
Registered: ‎02-17-2016

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

That is the marketing hype.

The specs say:

 

Untitled.jpg

 

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.

Reputable Contributor
Posts: 543
Registered: ‎10-18-2016

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

Yep that was clearly explained in my post and for me has never been a matter of debate..

The 50 mm example is an excellent one as it would be regarded as a "normal" lens on a FF body. But my point has been that the AoV of either lens on an APS-C body won"t be the same as for a FF. The AoV of both lenses will be Equivalent to that of an 80mm on a FF camera which is a telephoto performance.

Now if one wanted whatever the 50mm lens provided it wouldn't really matter, one would just take what it offered: i.e. a telephoto performance. The lens has not changed in any way whatsoever physically, but because of the crop format what it delivers is received differently. In essence it behaves differently eithout chaning its physical attributes.

But what if one actually specifically WANTS the AoV of a 50mm i.e ."normal"lens on the APS-C body. Well one would divide 50 by the crop factor of 1.6, coming out with the result that to get that AoV one would by a lens labelled as around 32mm.

Generally on talks about AoV using focal length not degrees of angle , so my point has been that when comparing the output performance of a lens across different sensor sizes one cannot take just the physical focal length (as written on the lens) at face value. That is the whole point of Equivalence.

In the end it's what the sensor receives that counts.
"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
"I have never been able to enlarge a photograph... I am just interested in the shots" Henri Cartier-Bresson
Reputable Contributor
Posts: 543
Registered: ‎10-18-2016

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

I think that on brochures the actual focal length should be printed along with ithe clearly identified Equivalence values. That might satisfy everyone! :-)

I think using Equivalence values is absolutely valid as long as it is understood for what it was intended.
"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
"I have never been able to enlarge a photograph... I am just interested in the shots" Henri Cartier-Bresson
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