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Registered: ‎12-06-2014
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Effects of using EF in EF-S camera and lens crop factor calculations.

I have read a lot about APS-C sensors and the differences between EF and EF-S lenses.

 

I still have two remaining questions regarding how EF-S lenses are marketed.

 

1) Do EF-S lenses need to have the 1.6x factor applied for effective focal length or are they marked correctly since they can only be used in APS-C cameras?

 

E.G. My 17-40mm EF 4L lens is effectively a 27.2-64mm when used in a EF-S mount camera due to the 1.6x factor.

 

So would a 60mm EF-S prime lens actually be similar to a 60mm EF prime lens in terms of focal and "zoomed" level of the image? Or would it also apply the crop factor and be effectively a 96mm focal length?

 

2) Are there any other attributes of an EF lens that you must apply a conversion when using in an EF-S mount? F-stop rating?

 

Thank you in advance for any guidance you provide!!

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Esteemed Contributor
Posts: 2,363
Registered: ‎11-14-2012

Re: Effects of using EF in EF-S camera and lens crop factor calculations.

The naming is fashoned as it was for 35 mm film cameras, and the crop factor isn't considered in naming the focal length / range of the lenses whether they have an EF or EF-S mount. a 60 mm is a 60 mm.

"A skill is developed through constant practice with a passion to improve, not bought."
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Posts: 5,313
Registered: ‎06-25-2014

Re: Effects of using EF in EF-S camera and lens crop factor calculations.


@techjedi wrote:

I have read a lot about APS-C sensors and the differences between EF and EF-S lenses.

 

I still have two remaining questions regarding how EF-S lenses are marketed.

 

1) Do EF-S lenses need to have the 1.6x factor applied for effective focal length or are they marked correctly since they can only be used in APS-C cameras?

 

E.G. My 17-40mm EF 4L lens is effectively a 27.2-64mm when used in a EF-S mount camera due to the 1.6x factor.

 

So would a 60mm EF-S prime lens actually be similar to a 60mm EF prime lens in terms of focal and "zoomed" level of the image? Or would it also apply the crop factor and be effectively a 96mm focal length?

 

2) Are there any other attributes of an EF lens that you must apply a conversion when using in an EF-S mount? F-stop rating?

 

Thank you in advance for any guidance you provide!!


If you feel obliged to think in full-frame terms even when using an APS-C camera, then yes, the crop factor is applied equally to zooms and primes. But unless you routinely use both types of camera, the mental exercise is really rather silly. Better to simply get used to the idea that on an APS-C camera a 30mm lens is "normal"; a 50mm lens is a mild telephoto or portrait lens; a 17-55mm zoom is a typical "walking around" lens; etc. Once you start thinking in those terms, you're much less likely to select the wrong lens than if you have to constantly apply the correction factor. If you do use both APS-C and FF cameras, you'll quickly get used to selecting, for example, the right normal lens for either type of camera, because you already know, in each case, what that is. At least that's what I've found to be true.

Bob
Philadelphia, Pennsylvania USA
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Registered: ‎02-28-2013

Re: Effects of using EF in EF-S camera and lens crop factor calculations.

+1 to what Bob said.  To Summarize: don't worry about it, it doesn't mean anything.  The only use is if you routinely use both FF and APS-C, and even then it's of limited value IMHO.

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Posts: 17
Registered: ‎12-06-2014

Re: Effects of using EF in EF-S camera and lens crop factor calculations.

Thanks for all the response.

 

Given your answers that the markings on the EF-S aren't adjusted already for the crop, I agree it doesn't matter. It would have mattered if having EF and EF-S lenses in my bag meant that I needed to adjust the mm of one so I knew which lenses I didn't need to carry, etc. Since that isn't the case, much easier!

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Re: Effects of using EF in EF-S camera and lens crop factor calculations.

So I am coming back to this thread because I still have one clarification for this question.

 

My wife's studio is not deep. The room's longest dimension is 12 feet and the mannequin sits just off the wall, so the farthest she can really stand back is about 10.5 feet.

 

Questions:

- Will a 50mm EF lens and a 50mm EF-S lens have the identical framing when standing at the same distance or would the EF version have to stand farther back on a EF-S camera to get the same content in frame?

- I am thinking of getting the Canon 60mm EF-S macro lens for her, would that be able to get the whole mannueqin in frame at 10.5 feet? (the mannequin is about 5' tall)

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Posts: 1,735
Registered: ‎02-28-2013

Re: Effects of using EF in EF-S camera and lens crop factor calculations.

Will a 50mm EF lens and a 50mm EF-S lens have the identical framing when standing at the same distance or would the EF version have to stand farther back on a EF-S camera to get the same content in frame?

 

There would be no difference (if a 50mm EF-S lens existed), 50mm is 50mm, so long as they were stuck on the same camera.  It's the camera's sensor size (full frame vs APS or "crop') that changes the field of view, not the lens.

 

There's no difference between EF and EF-S lenses, other than EF-S lenses cannot go on an EF camera (but EF lenses can go on EF-S cameras). If you're using a camera that can use both mounts (EF-S), then a focal length on a EF lens will be exactly the same as the focal length on an EF-S lens.  Technically the EF lens does provides a wider field of view, but your sensor is too small to take advantage of it, so it 'crops' it out.  Hence the moniker "crop sensor" camera.  EF-S lens simply trim out this 'wasted light' by providing a smaller field of view to begin with, one sized to work with your camera.

 

 

I am thinking of getting the Canon 60mm EF-S macro lens for her, would that be able to get the whole mannueqin in frame at 10.5 feet? (the mannequin is about 5' tall)

 

No.  It won't be wide enough.  According to the calculator I link below, you'd need 46.6mm lens, and that's without adding in some extra room for the border.  I'd call it 40mm to be safe.  60mm is too long for such a small room, even on the diagnol.

 

I wouldn't worry too much about full sized photos like that, use the wide angle you have now, or even the kit lens will be fine.  It's too far away to really take advantage of that macro lens anyway.  I recommended the macro for closeup of smaller items.  You'll really see the difference there.

 

http://www.cambridgeincolour.com/tutorials/camera-lenses.htm

 

 

 

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Re: Effects of using EF in EF-S camera and lens crop factor calculations.

The Canon EF-S 17-55mm f/2.8 IS USM Lens would be a good fit for you.

EOS 1DX and 1D Mk IV and several lenses!
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Re: Effects of using EF in EF-S camera and lens crop factor calculations.

[ Edited ]

Thank both of you for the information.

 

My hope was that the 60mm macro would be a great product lens as well as do the jewelry and authenticity tag macro work with great sharpness. My wife has to work quickly tho and it is a deal breaker to have to switch lenses or cameras when in a shooting session.

 

We will probably either continue with the kit lens and maybe try to swap her studio to a different room in the house that is deeper.

 

The 17-55 EF-S lens that ebiggs recommends is very similar to the kit lens in focal range. I notice it is a "faster" lens with fixed F which seems nice. Is it higher quality even when speed is not an issue due to the generous light from the flashes? It is pretty expensive, even compared to the 60mm macro.

 

Edit: Also should remind that we do have the 17-40mm 4L lens. Wouldn't this be better and similar to the 17-55?

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Registered: ‎02-28-2013

Re: Effects of using EF in EF-S camera and lens crop factor calculations.


@techjedi wrote:

Thank both of you for the information.

 

My hope was that the 60mm macro would be a great product lens as well as do the jewelry and authenticity tag macro work with great sharpness. My wife has to work quickly tho and it is a deal breaker to have to switch lenses or cameras when in a shooting session.

 

We will probably either continue with the kit lens and maybe try to swap her studio to a different room in the house that is deeper.

 

The 17-55 EF-S lens that ebiggs recommends is very similar to the kit lens in focal range. I notice it is a "faster" lens with fixed F which seems nice. Is it higher quality even when speed is not an issue due to the generous light from the flashes? It is pretty expensive, even compared to the 60mm macro.

 

Edit: Also should remind that we do have the 17-40mm 4L lens. Wouldn't this be better and similar to the 17-55?


The 17-55 has much better image quality than the kit lens, in certain conditions.  However, much of the added price is because of the wider aperture - f/2.8.  You don't need that for your wife's work, in fact, you shouldn't even be close to it.  Since you have light, and you're on a tripod, you can stop down.  At f/8, assuming you're not printing high resolution copies, you're going to see very little difference in the results between the two lenses.  Yes, if you zoom in on the picture you're going to see the 17-55 is a bit sharper, more detailed.  But are you, or your client really going to do this?  If this is all for web photos, it'd be a complete waste of money, in my opinion.

 

The 17-40 f/4 is not as good image quality as the 17-55, but it's better than the kit lens.  It does have a bit of distortion, but that can be fixed in post.  But again, stopped down to f/8, you're going to see relatively little difference in a websized photo.

 

A dedicate macro lens will produce noticeably different results than any of the above mentioned lenses, when getting close for detail shots of small objects.   But again, at f/8 and 10 feet away, you're not going to see much of a difference.

 

I would start with the lights, and your 17-40, and see how it works.  If it's not satisfactory, come back and tell us why and we'll recommend something else.  But I'm going to guess you'll be fine with either that or the kit lens.

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