As you may have seen I dropped my lens on its head on Friday. It was the kit lens that came with the camera - a 18-55mm (without IS).
I took it to the local shop today and the guy said he could sell me a new lens for cheaper (£89) than it would cost to have it repaired (about £110) - which by looking online is pretty competitive (he said it was from a kit he had split).
However, @mejbronant has kindly offered me the loan of a lens that she used on her old SLR (not digital). By what I understand one of the differences with using an old lens on a DSLR body is the size of the film compared to the sensor (x1.6 for Canon). Can anyone let me know of any other potential differences/problems with using an old lens on a DSLR?
If I've understood this properly (and please correct me if I'm wrong), if the lens I borrow is 18-55mm, it will actually behave like a 29mm-88mm. Is that right?
If that is the case I understand that I will not be able to take photos at such a wide angle, but not having been using an SLR of any kind for long enough to be able to imagine the difference, I wonder if someone would be so kind enough to take two photos of the same landscape for me, one at 18mm, and the other at around 29mm. I don't care how pretty the landscape is, all I'd like to see is the difference I should expect when the old lens arrives. Obviously I won't be able to compare when it arrives, as my own is broken!
By knowing this I'll be able to make a better judgement on justifying spending £89 on a new one or not!
The 18-55 you would borrow will behave as your 18-55 mm on your camera, that is as a 29-88 mm, it doesn't change anything (if I understand well your question). To use a 18-55 as a 18-55 you have to use it with a film SLR or with a full frame DSLR. So to make it short, you will be able to take the same pics as before.
About the quality, using a lens designed for a full frame on a smaller sensor is usually not a problem. What could make a difference is that recent lenses are differently treated/coated for digital use.
Why don't you try it and see if you like the result?
@lluniau Probably the biggest drawback is that you will have to use the older lens in mostly, if not entirely manual mode. I am assuming that the older lens is the same brand as your camera, or is a third-party lens with the correct "mount". FOr example, a nikon lens cannot mount onto a canon body.
In terms of an older, "full frame" lens mounted on the DSLR body, that should not be a problem. It's like a 50 mm disk sitting on top of a 40 mm disk - it will cover it. If it were the other way around, i.e. a 40 mm disk sitting on top of a 50 mm disk, you would notice that there would be a black circle around your image.
Hope this helps!! IN the end, I would match a new lens to your DSLR body - eliminates a bunch of problems.
@lluniau You have a pretty good understanding of how crop factors work with DSLR sensors, but my question is: what camera were you using to begin with?
The crop factor is a crop factor regardless of whatever lens you use. It doesn't matter that you are potentially using an older lens. The 18-55mm you dropped and broke (sorry 'bout that) would have also been 29-88mm. It makes no difference whatsoever whether the lens was made for digital or film.
The problem you may have with Canon is the lens mount. Canon likes to change their mounts every 5-6 years to "improve" the lens functions. Sometimes, older lenses will not work on newer bodies, so you may want to check that out first.
Thanks all three of you!
It sounds like I may have misunderstood (or been misled by) the guy in the shop... At the end of the day he was a salesman, and tried to sell me a 17-200mm instead!
@emsabh Using only manual will probably improve my skills quicker! (although I've been trying to mainly use manual anyway). AF will still work though, yes?!
@jasonbarnette I'm using an EOS 500D. The older lens I'm hoping to have on Wednesday (Mam's) was being used with an older EOS (and film) but I'm pretty sure it'll fit as her telephoto lens off the same camera fits my brother's EOS 550D.
i doubt the autofocus will work... i have a canon 30d and use analog lens all the time... the exposure meter inside the camera still works and i rely on that a lot and the sunny 16 rule-- i tend to shoot mostly for hdr so i use the aeb function and bracket most all my shots... you will need a dslr lens mount adapter there is no way to put slr onto a dslr without that.
There are two lens types with Canon cameras, EF and EF-S. The EF-S type are specifically designed for crop sensor cameras and cannot be used on a full frame camera. The EF lenses are designed for full frame but can be used on either.
The 18-55mm you damaged would have acted as an 18-55mm as it would have been an EF-S lens. The SLR lens will be an EF lens and will appear to be a 29-88mm lens although in fact is is still an 18-55mm - it's just that the sensor can't 'see' all of the image the lens projects.
All Canon EF and EF-S lenses are fully compatible whether they were designed for film or digital so you'll be just fine with it :)
Finally, Canon have only changed their lens mount system ONCE in the last 25 years and that was from ED to EF. They don't change mounts regularly.
Beware of older Sigma and Tamron lenses as they reverse engineer the control signals to make them work and may not be compatible with newer Canon digital cameras.
@islander Urgh...so you reckon what I understood at the beginning was right then? And that as a result I won't have as wide an angle shooting with the older lens as I did with the broken (new) one?
Either way, I'll have a go and see what happens.
Thanks!
I think people have complicated the issue here. Although your broken kit lens states that it's an 18-55mm, on your camera it was always a 29-88mm. Getting another lens that states 18-55mm will cover the same focal length.
@jasonbarnette Canon have only changed their mounts ONCE in their recent history, as @islander correctly points out.
@lluniau Yes, that's correct - it'll behave as a 29-88mm and you'll lose some of the wider end but gain a bit on the long end. If you want an 18-55mm to act as such then you'll need an EF-S.
@vikdaddy The kit lenses supplied with Canon APS-C sensor cameras are EF-S lenses designed for crop sensors and don't need the crop factor applied . The 17-55 that lluniau damaged would have effectively been a 17-55mm on that camera. It's only the EF lenses (or the equivalent on 3rd party makes) that the crop factor applies to :)
@islander Thanks again. I wonder (if you have time at some point) if you could take an example shots at these focal lengths (18 & 29) so that I can see how much the difference of 9mm actually makes to the result? (not to worry if you can't...I guess I'll soon figure out what it can do).
@lluniau Yes - I'll take a couple of shots for you. I don't have a 17-55 but I do have a 10-20mm and a 17-40mm so I can cover those focal lengths easily :)
Rubbish pics because the light was fading lol but you get the general idea. The buildings are about 100m away.
18mm focal length
29mm focal length
There is a slight difference but it's not that much to be honest. It would probably be more noticeable with a closer subject - I'll take a couple more of something close for you.
@islander You're a star! Thank you very very much for going to trouble. I'm sure I can cope with that. Can't wait to see @mejbronant (and her lens) on Wednesday!
@islander That's not true - if the lens itself states 18-55mm, it'll be a 29-88mm on a crop body. It does't matter if it's an EF or an EF-S lens. Remember, it's the CAMERA that makes the lens a x1.6 - not the lens.
"It is important to understand that the magnification factor still applies to EF-S lenses, which is why an "equivalent" or "apparent" focal length is often provided in the lens description...
...Canon's Digital Rebels like the XSi (450D) or T1i (500D) are usually offered with the EF-S 18-55mm f3.5-5.6 IS zoom lens as a "standard" lens. The equivalent focal length of this lens is 28.8-88mm, making it a pretty useful standard zoom, with focal lengths from moderate wide angle to short telephoto. The lens is also image-stabilized, an added bonus particularly at the longer end, or when shooting in low light at all focal lengths."
@lluniau Please see above - if the lens states it's a 18-55 then it WILL cover the same focal length as the kit lens you used to use. Don't let others confuse you!
EF-S lenses are designed and compensated for APS-C sensor cameras so if they say 17-55mm then that's their effective focal length on that sensor. They cannot be used on full frame sensor cameras -mainly because of physical differences in the rear element mounts, but if they could then they would cause extreme vignetting.
EF lenses are designed for full frame sensors and will also work on crop sensor cameras. However, if they are used on a crop sensor camera then the crop factor (either 1.3 for APS-H or 1.6 for APS-C) has to be taken into account.
It's both the camera AND the lens (sensor on camera, EF or EF-S format on the lens) that makes the difference. :)
@islander That's not true - please see link above. Have you read it? I have both EF and EF-S lenses, and whilst you're correct that the EF-S lenses do not work on full frame bodies, the EF lenses do on crop bodies.
Canon have created what seems like unusual focal lengths (such as 18-55) in the digital world because when they're used on a crop body it works as a 29-88mm, which is a nice range. This covers a more standard focal length in the film world (such as the 24-85mm lens I have).
I use both EF and EF-S equivalent lenses in my 40D. My EF-S 10-20mm gives a true 10mm UWA view whereas my EF 17-40L gives a 27.2mm view at it's widest - which is why many professionals consider it to be a waste of time on a crop (I respectfully disagree with this POV ;) )
At the 20mm end my EF-S 10-20mm is STILL wider than my EF 17-40L.
"Manufacturers have responded to this “zooming effect” by offering a new type of lens specifically designed for crop cameras. Canon calls theirs EF-S lenses while Nikon refers to them as DX lens. In either case they are typically wider to compensate for the effects of the smaller sensor. Lenses such as the Canon 10-22mm would be considered almost a fisheye on a full frame camera, but on the crop camera is equates to 16-35mm or just a wide angle."
"It's for this reason that Canon has recently added a number of EF-S lenses to its range. These are specifically designed for Canon digital SLRs with the APS-C sensor and are aimed at countering the magnification factor on the wide angle side. A good example is the Canon EF-S 10-22mm f/3.5-4.5 USM, which equates to a 16-35mm ultra wide on a full-frame body."
@islander It doesn't - your 10-22 is effectively a 16-35. I have the same lens! Yes the 17-40 would cover a more 'standard' range (something like a 24-62), but that doesn't mean the 10-22 truly begins at 10mm. Please see above evidence. It says all over the Web!
I'll trust my own eyes. 17mm on my EF is NOT as wide as 20mm on my EF-S. Likewise my 100mm EF is longer than my rubbishy 100-300mm EF-S at the short end.
They are designed and compensated for the APS-C sensor giving a narrower field of view at the prime focus - try them on a FF and assuming that the short back focus (which is what the S stands for) doesn't wreck the mirror, and you'll have a badly vignetted image.
Use a 17-55mm EF-S and a 17-55 EF on an AP-C camera and you'll see a difference.
Perhaps we're talking at cross-purposes. What I am stating is that an EF-S lens that states 18-55 is NOT actually an 18-55 on a crop body, but something like 29-88mm. However if there was such a thing as an EF lens that was 18-55, it WOULD actually be 18-55 on a full frame body (but still 29-88 on a crop body).
So, in effect ANY lens she uses on her camera would be 'cropped'. Old or new, if it fits the mount she would need to multiply the focal length by x1.6.
An 18-55mm lens is an 18-55mm lens on an APS-C, APS-H or FF body. A focal length is a focal length is a focal length.
EF-S lenses have their field of view corrected for APS-C sensors so that they project the same(ish) field of view as the same focal length on an EF on a FF camera. Put an EF-S lens on a FF and you get vignetting. Put an EF on an APS-C and you only use a fraction of the field of view. Hence the crop factor for an EF lens on an APS-C or APS-H.
There's no misleading here whatsoever - the OP will notice a difference with an EF lens (which the film SLR lens will be) compared to an EF-S lens. They may have the same *real* focal length, but the effective field of view is different and it's noticeable.
Gah. As I said before an 18-55mm is an 18-55mm whether it's on a crop or a FF. The focal length remains the same for BOTH sensors. What changes is the field of view and on an EF-S lens, that is compensated for the smaller sensor in an APS-C crop to give the equivalent field of view to an EF lens on a FF camera.
Take an EF 18-55 and an EF-S 18-55 and put both on a FF camera (let's assume this is possible) both lenses are 18-55mm focal length but the EF-S will vignette very badly because of its compensated field of view whereas the EF will give a perfect field of view and behave as a normal 18-55 lens.
Now put both on an APS-C (1.6 crop) camera and see what happens. The compensated field of view of the EF-S lens now matches the sensor size and you get a normal 18-55mm field of view. Put the EF lens on and you only see a small amount of the field of view available at the same focal length - i.e. a *smaller* area because of the reduced sensor size.
The OP will notice a difference in the field of view available between the EF and EF-S lenses and that will manifest itself as an apparent loss of wideness at the low end and some apparent additional length at the high end. It's still an 18-55 though - there's no magical change in the real focal length.
I've now explained this in as many ways as I can think of. There is a difference in the field of view available at the prime focus of each type of lens (EF or EF-S) designed to match a particular sensor size and that makes a difference when a non-crop lens (EF) is used on a crop sensor. If EF-S lenses were suitable for FF bodies then they wouldn't be used anyway - unless you particularly like vignetting and the edge distortion that accompanies it :p
So you are saying that if I put "EF-S" 18-55 lens on 60D (APS-C cropped sensor) at the "18mm" end I will get the same image coverage area as I use a EF 16-35mm at 18mm on a 5D (Full-Frame sensor)?
I'll chime in, only because this thread is now annoying me. ;)
Vikdaddy is spot-on. EF-S lenses are optimised for APS-C sensors, but the focal lengths are measured the same way as for EF lenses. In fact, by removing just a gasket (and being very, very careful) you can mount the EF-S 10-22mm lens on a FF camera and, surprise surprise, it behaves exactly as a 10-22mm lens. The lenses do not affect the field of view - the sensors do that.
18-55, whether EF or EF-S, will behave identically on a crop-frame camera. The only difference between the two is the optimisation (typically, the rear element is too far back to mount an EF-S lens on a FF camera, as it will damage the mirror), and any extra vignetting caused by (the questionable logic of) mounting an EF-S lens on a FF camera is due to the positioning of said rear element and has nothing to do with the lens "cropping the shot".
They (Canon) do not print "effective" focal lengths on their lenses - they print the actual, physical, focal lengths. Effective focal lengths are caused by sensor size, and have nothing to do with EF or EF-S designations.
Photographic examples to hopefully remove any doubt:
I took a series of four images, using a tripod, of a static object. Each of the first three images make use of different lenses, all set at (or as close as possible to) 50mm, on a 400D (crop-frame Canon camera). The fourth image is with a different camera (full-frame 5D Mark II), but one of the same lenses, set to the same 50mm focal length.
This first image is on the 400D, taken with an EF 50mm f/1.4 lens. This is a prime lens, so the focal length is always 50mm.
The next image was taken with an EF 24-70 f/2.8 L zoom lens, set at 50mm. You can see from the metadata that it actually was 50mm, as marked on the lens. This shot is really just to show that 50mm on a prime is 50mm on a zoom. This lens is much heavier and the extra weight tilted the angle down slightly - you will notice the top of the frame shifted the same amount as the bottom of the frame, between shots.
The next image is taken with the same camera, having not removed it from the tripod nor having moved the tripod, but this time using the EF-S 18-55mm lens as described by the OP. There is no 50mm mark on the lens, so I had to guess it. I actually took several shots, adjusting the zoom very slightly, to try to hit the 50mm mark. I didn't get it, but I got 49mm which is plenty close enough.
This last shot was taken with the EF 24-70 f/2.8 lens, set at 50mm once again, but this time on my 5D Mark II full-frame (35mm sensor) camera. You will notice the wider angle caused by the physically larger sensor. You will also notice that the DOF and compression details are identical - sensor size does not affect DOF directly (the way you compose your shots with said larger format cameras is what does it, because you stand closer to your subject if using the same focal length as on a crop-frame camera).
I can't show you the effect of an EF-S lens on my full-frame camera because I am not about to void my camera's warranty (or damage it)! Suffice to say, it would still look the same at 50mm, if I managed it without wrecking my kit.
So, 50mm on an EF lens = 50mm on an EF zoom lens = 50mm on an EF-S zoom lens. 50mm is 50mm! It is the sensor that crops the image, regardless of the lens mount designation. That is because 50mm is a physical distance (how far the light travels within the lens). Any tiny variations are there either because I wasn't careful enough to not bump the tripod, or because there are slight variations between lenses (you can look up the lens patents to see what I mean - 50mm could be 49.3mm, for example, for a given lens, and 50.7mm on another).
Hey guys, please stop arguing on my account. I feel awful for this. Although I'm extremely grateful to all of you for taking the time to answer my query (and I can see that all of you have!), I wouldn't like to think that the matter has caused any ill-feeling between anyone.
I'm borrowing this old lens, so no one will be blamed for misleading me into buying anything. And if there is a difference between it, and the one I'm used to, through @islander 's photos, I can see that it isn't a difference great enough to be a problem for me at my level of photography.
I don't think we're arguing, I think it's just a vigorous debate. Anyway, the truth will out and you now know that the lens you use will work the same irrespective of whether it's an EF or EF-S lens.
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About the quality, using a lens designed for a full frame on a smaller sensor is usually not a problem. What could make a difference is that recent lenses are differently treated/coated for digital use.
Why don't you try it and see if you like the result?
In terms of an older, "full frame" lens mounted on the DSLR body, that should not be a problem. It's like a 50 mm disk sitting on top of a 40 mm disk - it will cover it. If it were the other way around, i.e. a 40 mm disk sitting on top of a 50 mm disk, you would notice that there would be a black circle around your image.
Hope this helps!! IN the end, I would match a new lens to your DSLR body - eliminates a bunch of problems.
The crop factor is a crop factor regardless of whatever lens you use. It doesn't matter that you are potentially using an older lens. The 18-55mm you dropped and broke (sorry 'bout that) would have also been 29-88mm. It makes no difference whatsoever whether the lens was made for digital or film.
The problem you may have with Canon is the lens mount. Canon likes to change their mounts every 5-6 years to "improve" the lens functions. Sometimes, older lenses will not work on newer bodies, so you may want to check that out first.
Make sense?
Thanks all three of you!
It sounds like I may have misunderstood (or been misled by) the guy in the shop... At the end of the day he was a salesman, and tried to sell me a 17-200mm instead!
@emsabh Using only manual will probably improve my skills quicker! (although I've been trying to mainly use manual anyway). AF will still work though, yes?!
@jasonbarnette I'm using an EOS 500D. The older lens I'm hoping to have on Wednesday (Mam's) was being used with an older EOS (and film) but I'm pretty sure it'll fit as her telephoto lens off the same camera fits my brother's EOS 550D.
The 18-55mm you damaged would have acted as an 18-55mm as it would have been an EF-S lens. The SLR lens will be an EF lens and will appear to be a 29-88mm lens although in fact is is still an 18-55mm - it's just that the sensor can't 'see' all of the image the lens projects.
All Canon EF and EF-S lenses are fully compatible whether they were designed for film or digital so you'll be just fine with it :)
Finally, Canon have only changed their lens mount system ONCE in the last 25 years and that was from ED to EF. They don't change mounts regularly.
Beware of older Sigma and Tamron lenses as they reverse engineer the control signals to make them work and may not be compatible with newer Canon digital cameras.
Either way, I'll have a go and see what happens.
Thanks!
@jasonbarnette Canon have only changed their mounts ONCE in their recent history, as @islander correctly points out.
18mm focal length
29mm focal length
There is a slight difference but it's not that much to be honest. It would probably be more noticeable with a closer subject - I'll take a couple more of something close for you.
Guitar was about 1m away.
18mm focal length
29mm focal length
The difference is more obvious with these two.
Hope this helps anyway :)
http://www.wildlife-pictures-online.com/canon-ef-s-lenses.html -
"It is important to understand that the magnification factor still applies to EF-S lenses, which is why an "equivalent" or "apparent" focal length is often provided in the lens description...
...Canon's Digital Rebels like the XSi (450D) or T1i (500D) are usually offered with the EF-S 18-55mm f3.5-5.6 IS zoom lens as a "standard" lens. The equivalent focal length of this lens is 28.8-88mm, making it a pretty useful standard zoom, with focal lengths from moderate wide angle to short telephoto. The lens is also image-stabilized, an added bonus particularly at the longer end, or when shooting in low light at all focal lengths."
EF-S lenses are designed and compensated for APS-C sensor cameras so if they say 17-55mm then that's their effective focal length on that sensor. They cannot be used on full frame sensor cameras -mainly because of physical differences in the rear element mounts, but if they could then they would cause extreme vignetting.
EF lenses are designed for full frame sensors and will also work on crop sensor cameras. However, if they are used on a crop sensor camera then the crop factor (either 1.3 for APS-H or 1.6 for APS-C) has to be taken into account.
It's both the camera AND the lens (sensor on camera, EF or EF-S format on the lens) that makes the difference. :)
Canon have created what seems like unusual focal lengths (such as 18-55) in the digital world because when they're used on a crop body it works as a 29-88mm, which is a nice range. This covers a more standard focal length in the film world (such as the 24-85mm lens I have).
At the 20mm end my EF-S 10-20mm is STILL wider than my EF 17-40L.
http://www.pixelatedphotographer.com/crop-factor-explained:
"Manufacturers have responded to this “zooming effect” by offering a new type of lens specifically designed for crop cameras. Canon calls theirs EF-S lenses while Nikon refers to them as DX lens. In either case they are typically wider to compensate for the effects of the smaller sensor. Lenses such as the Canon 10-22mm would be considered almost a fisheye on a full frame camera, but on the crop camera is equates to 16-35mm or just a wide angle."
http://www.wildlife-pictures-online.com/canon-crop-factor.html:
"It's for this reason that Canon has recently added a number of EF-S lenses to its range. These are specifically designed for Canon digital SLRs with the APS-C sensor and are aimed at countering the magnification factor on the wide angle side. A good example is the Canon EF-S 10-22mm f/3.5-4.5 USM, which equates to a 16-35mm ultra wide on a full-frame body."
They are designed and compensated for the APS-C sensor giving a narrower field of view at the prime focus - try them on a FF and assuming that the short back focus (which is what the S stands for) doesn't wreck the mirror, and you'll have a badly vignetted image.
Use a 17-55mm EF-S and a 17-55 EF on an AP-C camera and you'll see a difference.
@vikdaddy I think we'll have to agree to disagree on this one ;)
http://en.wikipedia.org/wiki/Canon_EF-S_lens_mount - Look at the table which shows the actual focal lengths
Perhaps we're talking at cross-purposes. What I am stating is that an EF-S lens that states 18-55 is NOT actually an 18-55 on a crop body, but something like 29-88mm. However if there was such a thing as an EF lens that was 18-55, it WOULD actually be 18-55 on a full frame body (but still 29-88 on a crop body).
So, in effect ANY lens she uses on her camera would be 'cropped'. Old or new, if it fits the mount she would need to multiply the focal length by x1.6.
EF-S lenses have their field of view corrected for APS-C sensors so that they project the same(ish) field of view as the same focal length on an EF on a FF camera. Put an EF-S lens on a FF and you get vignetting. Put an EF on an APS-C and you only use a fraction of the field of view. Hence the crop factor for an EF lens on an APS-C or APS-H.
There's no misleading here whatsoever - the OP will notice a difference with an EF lens (which the film SLR lens will be) compared to an EF-S lens. They may have the same *real* focal length, but the effective field of view is different and it's noticeable.
Note in the table from the link:
-Focal length 18-55mm
-35mm equivalent focal length (APS-C) 29-88mm
-Diagonal angle of view(APS-C) 74° - 27°
http://www.dpreview.com/lensreviews/canon_18-55_3p5-5p6_is_c16/
Take an EF 18-55 and an EF-S 18-55 and put both on a FF camera (let's assume this is possible) both lenses are 18-55mm focal length but the EF-S will vignette very badly because of its compensated field of view whereas the EF will give a perfect field of view and behave as a normal 18-55 lens.
Now put both on an APS-C (1.6 crop) camera and see what happens. The compensated field of view of the EF-S lens now matches the sensor size and you get a normal 18-55mm field of view. Put the EF lens on and you only see a small amount of the field of view available at the same focal length - i.e. a *smaller* area because of the reduced sensor size.
The OP will notice a difference in the field of view available between the EF and EF-S lenses and that will manifest itself as an apparent loss of wideness at the low end and some apparent additional length at the high end. It's still an 18-55 though - there's no magical change in the real focal length.
I've now explained this in as many ways as I can think of. There is a difference in the field of view available at the prime focus of each type of lens (EF or EF-S) designed to match a particular sensor size and that makes a difference when a non-crop lens (EF) is used on a crop sensor. If EF-S lenses were suitable for FF bodies then they wouldn't be used anyway - unless you particularly like vignetting and the edge distortion that accompanies it :p
I'm happy to let the OP decide for herself :D
So you are saying that if I put "EF-S" 18-55 lens on 60D (APS-C cropped sensor) at the "18mm" end I will get the same image coverage area as I use a EF 16-35mm at 18mm on a 5D (Full-Frame sensor)?
Vikdaddy is spot-on. EF-S lenses are optimised for APS-C sensors, but the focal lengths are measured the same way as for EF lenses. In fact, by removing just a gasket (and being very, very careful) you can mount the EF-S 10-22mm lens on a FF camera and, surprise surprise, it behaves exactly as a 10-22mm lens. The lenses do not affect the field of view - the sensors do that.
18-55, whether EF or EF-S, will behave identically on a crop-frame camera. The only difference between the two is the optimisation (typically, the rear element is too far back to mount an EF-S lens on a FF camera, as it will damage the mirror), and any extra vignetting caused by (the questionable logic of) mounting an EF-S lens on a FF camera is due to the positioning of said rear element and has nothing to do with the lens "cropping the shot".
They (Canon) do not print "effective" focal lengths on their lenses - they print the actual, physical, focal lengths. Effective focal lengths are caused by sensor size, and have nothing to do with EF or EF-S designations.
@islander Looks like you're in the minority... Not singling you out, I just want the person who started the thread not to be misled.
Photographic examples to hopefully remove any doubt:
I took a series of four images, using a tripod, of a static object. Each of the first three images make use of different lenses, all set at (or as close as possible to) 50mm, on a 400D (crop-frame Canon camera). The fourth image is with a different camera (full-frame 5D Mark II), but one of the same lenses, set to the same 50mm focal length.
This first image is on the 400D, taken with an EF 50mm f/1.4 lens. This is a prime lens, so the focal length is always 50mm.
The next image was taken with an EF 24-70 f/2.8 L zoom lens, set at 50mm. You can see from the metadata that it actually was 50mm, as marked on the lens. This shot is really just to show that 50mm on a prime is 50mm on a zoom. This lens is much heavier and the extra weight tilted the angle down slightly - you will notice the top of the frame shifted the same amount as the bottom of the frame, between shots.
The next image is taken with the same camera, having not removed it from the tripod nor having moved the tripod, but this time using the EF-S 18-55mm lens as described by the OP. There is no 50mm mark on the lens, so I had to guess it. I actually took several shots, adjusting the zoom very slightly, to try to hit the 50mm mark. I didn't get it, but I got 49mm which is plenty close enough.
This last shot was taken with the EF 24-70 f/2.8 lens, set at 50mm once again, but this time on my 5D Mark II full-frame (35mm sensor) camera. You will notice the wider angle caused by the physically larger sensor. You will also notice that the DOF and compression details are identical - sensor size does not affect DOF directly (the way you compose your shots with said larger format cameras is what does it, because you stand closer to your subject if using the same focal length as on a crop-frame camera).
I can't show you the effect of an EF-S lens on my full-frame camera because I am not about to void my camera's warranty (or damage it)! Suffice to say, it would still look the same at 50mm, if I managed it without wrecking my kit.
So, 50mm on an EF lens = 50mm on an EF zoom lens = 50mm on an EF-S zoom lens. 50mm is 50mm! It is the sensor that crops the image, regardless of the lens mount designation. That is because 50mm is a physical distance (how far the light travels within the lens). Any tiny variations are there either because I wasn't careful enough to not bump the tripod, or because there are slight variations between lenses (you can look up the lens patents to see what I mean - 50mm could be 49.3mm, for example, for a given lens, and 50.7mm on another).
I hope that helps.
I'm borrowing this old lens, so no one will be blamed for misleading me into buying anything. And if there is a difference between it, and the one I'm used to, through @islander 's photos, I can see that it isn't a difference great enough to be a problem for me at my level of photography.
Time out guys!
Elin xx