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by Bart Arondson

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I see a lot of questions comparing full frame (e.g EF for Canon, FX for Nikon) and crop lenses (e.g. EF-S for Canon, DX for Nikon) but I can't find the answer to what would be the differences between the photos taken with say a 50mm f/1.4 EF and EF-S lenses both used with

  • same APS-C sensor sized camera
  • same ISO
  • same f/1.4 f-stop
  • same focal length
  • same shutter speed

What would be the resulting differences in the photos? Which one would

  • be brighter than the other due the EF-S lens concentrating the light more? no that's wrong. Both put the same amount of light from the same FoV on the sensor.
  • have greater depth-of-field? neither
  • less problems towards the edges? generally the full frame
  • more lens flare? generally the full frame lens unless there is, or you provide more shading
  • anything else? not really, unless you start down the road of which one is typically of better build quality.

Edit: Added the answers from what seems to be the general consensus from the multiple answers and comments.

Results: My desire to buy a fast medium-high quality lens compatible with both full frame and crop camera's doesn't have to be hampered by the APS-C sensor size of my current camera. This means I'm willing to part with more money to get a higher performance/quality lens as the performance/quality will be useful now and when I upgrade my camera. Though reading reviews of some full frame lenses with short focal lengths, look out, as some are really only made to perform well on crop cameras even though they fit on a full frame camera and will give you a full frame picture, the edge quality is very bad.

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Would you mind if I edited the question to remove the Canon-specific terminology? As I note in my answer, there's nothing system-specific here and I think that would make it a better question going forwards. –  Philip Kendall Jan 16 at 8:44
    
sure, I don't know the non-system specific terms for EF vs EF-S lenses –  BeowulfNode42 Jan 16 at 8:46
    
The EF vs EF-S terminology does allow a significant amount of 'shorthand' when discussing the issue. –  Michael Clark Jan 16 at 8:50
    
So would the FX/DX terminology. Both might be unfamiliar to beginners (I only recently became aware of Nikon's terms), so I think using the "proper" terms in the actual question plus the company specific terms is a better approach for this site. (And FF vs. crop isn't really longer.) –  Cornelius Jan 16 at 11:54

5 Answers 5

You can get more lens flare using a full frame lens on a smaller sensor when shooting close to the sun or other lightsources.

The reason for this is simply the APS-C lens has a narrower field of view and so a lightsource just out of frame has no physical path through the lens. If you're using a full frame lens with the same composition then there is a path through the lens, even though the light doesn't fall onto the sensor directly (since it's smaller than full frame), it can bounce off the inside of the camera, off the rear lens element and back onto the sensor where it will reduce the contrast of your image.

This only happens when the lightsource is very bright, e.g. the sun, or a strong nearby light at night. It can be avoided by shading the lens with your hand.

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This does assume the APS-C lens is shielded from out of frame light sources striking the front element that would fall within the FoV of the FF lens. That is not always the case. In general lenses designed for FF use include more effective coatings on the lens elements and other design features meant to inhibit flare. –  Michael Clark Jan 16 at 9:14
1  
@MichaelClark APS-C lenses aren't perfectly shielded from out-of-frame light, that's true, but they're a hell of a lot more shielded than full frame lenses which would let 100% of the light into the lens, and out the other side to bounce around the mirror box! –  Matt Grum Jan 16 at 12:43
    
@MichaelClark also, I don't think you can say in general that FF lenses use more effective coatings, or are more flare proof than APS-C lenses, there are good and bad examples for both formats. Certainly the difference in coating performance is much smaller than the difference in flare that results from the narrower angle of view! –  Matt Grum Jan 16 at 12:45
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As something of an exception to prove the rule, a few of Sigma's long lenses designed for 135-format sensors include hood extensions intended for use with crop-sensor cameras. –  mpr Jan 16 at 13:18
    
Perhaps 'in general' was not the best choice of words. But since EF-S/Dx/etc. lenses are almost exclusively zoom lenses, they are inherently subject to flare in a way practically no FF prime lens would be. And of the FF zoom lenses I own, which are admittedly not lower end consumer grade lenses, they perform much better with regard to flare than the EF-S zoom lenses I have owned. –  Michael Clark Jan 16 at 15:38

No. The only difference between a 50mm EF lens and a 50mm EF-S lens as it relates to the issues your question raises is the size of the image circle it projects. Assuming a similar optical design and use of materials of a similar quality, the portion of the image circle projected by the full frame lens would be the same as the image circle projected by the APS-C lens.

An EF-S lens does not concentrate more light into a smaller circle than an EF lens does. The EF lens collects more light because it collects it from a wider angle of view that is then spread over a larger image circle, but the same amount of light falls on an APS-C sensor with either lens because only the same angle of view is provided by the full frame lens when using an APS-C sensor.

If one were to use an EF and EF-S lens of the same focal length on the same APS-C camera set to the same ISO and using the same aperture there would be absolutely no difference in terms of brightness or depth of field (or angle of view). The amount of edge sharpness would depend on the comparative optical quality of each design. If the elements of each lens that contribute to the part of the image projected onto the APS-C sensor were identical, there would be absolutely no difference.

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less problems towards the edges?

The full frame lens will have better edge performance on the crop sensor relative to the crop lens on that same crop sensor. This is due to the full frame performance is designed to be spread across a larger sensor, thus you are get more of the inner sweat-spot, when using a full frame lens on a crop.

But you are also carrying heaver glass, and it was cost more to purchase in the first place.

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I think the last point depends a lot on the type of lens you're talking about; for example, the vast majority of both the weight and the cost of telephoto lens is in the front element. Even if anybody made a crop-specific (say) 400mm f/2.8 it wouldn't be significantly cheaper or lighter than the full-frame version - which is of course why it's not made. –  Philip Kendall Jan 16 at 10:32
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Actually the largest cost is usually in the front group, but not the front element. The corrector lens that is most often made of the most exotic/expensive material is usually the next to last lens element in the front group. –  Michael Clark Jan 16 at 12:21
    
Simeon, you nailed it. –  TFuto Jan 16 at 13:21
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You can't say "The full frame lens will have better edge performance relative to the crop lens on that same crop sensor" without knowing the properties of both lens designs. –  Marco Mp Jan 16 at 14:52
    
@MarcoMP your correct, you cannot say anything in life. But on the whole most crop lens performance at the edge is falls off like those of the full frame, but given the full frames edge is beyond the crop sensor, you end up with "better" results. –  Simeon Pilgrim Jan 16 at 20:08
  • be brighter than the other due the EF-S lens concentrating the light more?

No. For any given exposure, the light intensity at the sensor is identical and independent of anything to do with sensor size or lens format.

  • have greater depth-of-field?

No. Depth of field is determined by the size of the sensor, not the size of the lens.

  • less problems towards the edges?

Yes and no. In general, using an lens designed for a full-frame camera (e.g. EF for Canon, FX for Nikon) on a crop camera results in less aberrations and vignetting in the corners, because what you're looking at is just the central part of the image projected by the lens, and it's been designed to be not too bad even in the corners of the full-frame image. However, your original premise ("using 50mm f/1.4 EF and EF-S lenses") is broken here because they would have to be two different lenses and therefore designed differently.

Note that there's nothing specific to Canon about your question other than the EF / EF-S terminology. The same answers would apply to any other system where you can mount full-frame lenses on a crop sensor, most notably Nikon FX lenses on a DX camera.

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since f-stop is the ratio of entrance pupil aperture and focal length, doesn't this mean all 50mm f/1.4 lenses will have the same entrance pupil aperture, but the EF-S puts all of that light on a smaller area? if so wouldn't that be brighter? –  BeowulfNode42 Jan 16 at 8:46
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The angle of view that the light projected onto the smaller sensor is collected from is also correspondingly narrower as well. –  Michael Clark Jan 16 at 8:53
    
No. An EF-S 50mm lens captures less light than the EF version in the first place as it's got a narrower field of view. If you compared a (50/1.6) = 31mm f/1.4 EF-S lens to a 50mm f/1.4 EF lens to get equivalent framing, then that's a different question. –  Philip Kendall Jan 16 at 8:53
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@PhilipKendall - I believe that you're mixing two different things in your comment - FoV is determined by both Focal length and sensor size. Both 50mm lenses, mounted on an APS-C camera will generate the same FoV, and gather the same amount of light. –  ysap Jan 16 at 10:16
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Suffice it to say that the sensor sees the same amount of light from the same FoV with either lens. –  BeowulfNode42 Jan 17 at 3:38

EF-s lenses do not concentrate light any more than an EF lens, they simply crop the area of light that they take in and put out. An EF-s lens takes in less light than an EF lens because it does not need to paint a full image circle. While I'm oversimplifying a bit, an EF-s lens is basically just taking the center portion of an EF lens but otherwise not altering it at all, so light intensity, depth of field, etc, all stay the same.

You may get differences in the edge quality because lenses since lenses tend to be designed such that you get the most distortion near the edges, however that also depends on the relative quality of the lenses. If you took an EF lens on a FF camera vs that same EF lens on a crop body, you'd almost always have less edge distortion, but with different lenses, it is entirely possible that the EF lens could be sharper on the edges than the EF-s lens is in the center.

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How is an EF-S lens more complicated optically? If anything the opposite is the case. Assuming the same focal length, the smaller the diameter of the entrance pupil, the less correction needs to be made for CA, distortion, vignetting, etc. –  Michael Clark Jan 16 at 15:45
    
@MichaelClark - whoops, multiple possible meanings to what I was saying. I meant that what is actually going on is more complicated than simply cutting the edges. I changed the phrasing to hopefully make it more clear. –  AJ Henderson Jan 16 at 15:49

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