Ef-s focal length

Hello all, I am a little confused.

The local seller here said me that when you have a EF-s lens, it can only fit on croped boddys, so the focal length of these lenses is allready converted. So, the 18 to 55 would be not a 29 to 88.

Neverteless when i watch the internet, they still talk about convering these lenses.

So, can you guys help me out, and tell me the real truth about the focal length in EF-s lenses.

Thanks in advance

Telhma

The dealer is correct. Either an EF or EFS lens stated focal length is the same. The equivalency/conversion you see in conversations only applies to angle of viewing compared to full frame cameras.

Some old crop cameras do not accept EF-S lenses (cameras prior to 20D).

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Olga

This issue comes up over an over again.

The focal length of a lens is fixed property of the lens and is independent of camera format.

But, the angle of view yielded by a lens of a given focal length will vary with camera format, so lots of folks talk about full frame "equivalent" focal lengths.

So, an 18mn lens is an 18mm lens on either a full frame or a crop. But, an 18mm lens on crop will yield an angle of view equivalent to what you'd get with a 29mm lens on a full frame camera. As such, an 18mm lens on a crop is a wide angle, but if you put an 18mm lens on a full frame, it's an ultra wide angle.

okej, but what i wanted to know is, if you have a EF-s lens focal length 100mm, will it give the same result as i usse a EF lens focal length 100mm.

greets

If you use an EF-S 100mm lens on a crop, it will yield the same angle of view as an EF 100mm lens on a crop.

The difference between an EF-S and EF lens is that the EF-S lens produces a smaller image circle since it only needs to cover the smaller crop sensor. Most EF-S lenses also protrude further into the camera than EF lenses and could interfere with a full frame camera's mirror if you tried to use them on a full frame.

60 f2.8 - great EF-s lens will only work on 1.6 crop.  It has a field of view of 100mm FOV when compared to a 100 L EF lens on a FF camera.  EF lenses work on both crop and FF cameras.  Just multiply by 1.6 when lenses are put on crop cameras to do the comparison with FF cameras.

This is interesting. As a relative beginner, I understood the crop-FF conversion figures to mean an increase in FL. What you are saying, is that, as far as FL [not FOV] is concerned, a, say 100mm EF lens on a FF, will give the same magnification [apologies if that is not the correct term] of, say a bird, as a 100mm EF-s lens on a crop body. Hence only the FOV is affected?which means the amount of the scene in the frame is greater with the FF? So if I "cut out" the 1.6, from the FF image, the bird would be the same size as the same shot taken with the 1.6 crop camera? I am sorry if I am not explaining this correctly, but I thought a 100mm lens on a crop made the subject appear closer than a 100mm lens on a FF body. Sorry, it would be so much easier for me to express myself face to face or over the phone than in written form. Thank's for being patient, if I have this right, it is a "Eureeka" moment for me in photography.

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lee uk.
There are old pilots, & there are bold pilots, but there are no old bold pilots.

If you are a beginner and have gotten through all the discussion of this topic and have come to this understanding you are doing really well, and you are correct.

The difference between sensors on FF cameras, vs APS-C in the case of Canon, is simply cropping.

Think of it this way-A lens is simply "projecting" an image onto the sensor. Using the same lens to subject distance a 100mm lens will project the same size image on any body. If you aimed it at a coin, and the coin image measured 1/4 inch on the sensor, it would measure 1/4 inch on any sensor.

The FF body has a bigger sensor so there is more room around the coin; the crop body has a smaller sensor so there is less room around it.

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Ross Attix

Thank you Ross. I am cellibrating this with a glass [or 2] of Jim Beam, neat, no ice. Feel I deserve it!!!!

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lee uk.
There are old pilots, & there are bold pilots, but there are no old bold pilots.

Read the following thread and you'll be an expert:

http://forums.dpreview.com/forums/post/50644089

to summarize equivalency principles -

- the distance between the photographer and the subject remain the same- ie, you can't be in two places at one time. You are asking yourself what would it be like to photograph with a FF camera and a good lens and get the same picture with a 1.6 crop camera.

- you must achieve the same frame- field of view (FOV).

- usually people use 17-55 vs 24-105 to compare as in the above thread, but I'll use 60 f2.8 EF-s on crop to compare with 100L on FF.

- think multiply crop by 1.6.

- 60 macro on crop camera times 1.6 becomes 96 FOV as compared to a 100mm L lens on a FF camera. Both are seeing about the same frame size in the scene from the same position from the subject (same perspective).

- now multiply the 60 macros F2.8 by 1.6 to get F4.5 - DOF. So crop is deeper dof than FF 100L F2.8. So F2.8 is not F2.8 for equivalency purposes. F2.8 FF is F4.5 Crop

- now to keep the shutter speeds equal, you must raise the iso on the FF camera. You must raise it by 1.6 squared. So 1.6x1.6= 2.56. So if your crop camera is ISO = 100, you must raise the FF camera to ISO 250.

there you have it - equivalency summarized.

btw I have both a 60 F 2.8 macro on my T4i and a 100F2.8 L on my 5D and love both setups.

-

Thank's for the link & explanation. I think the confusion arises when posters say things like, "This 200mm is equivalent to 300mm on FF". Beginners like myself tend to think only that the 300 is a longer FL [obviously] so therefore brings the subject closer, in telescopic terms anyway. The more experienced realise that it's the FOV that is being compared, not the FL, which, naturally doesnt change. It has taken 15 months & reading dozens of threads & posts, for this to finally sink in! "Knowledge, I love it" [Slight twist on Lt. Commander Data's "Humour, I love it" line in Star Trek Next Generation.]

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lee uk.
There are old pilots, & there are bold pilots, but there are no old bold pilots.

Already converted? No. He is wrong, does not understand it. The 18-55mm is not converted in any way. it is exactly the same as a 18-55mm EF lens would be, focal length wise.

Focal lengths are focal lengths, if you put an EF-S lens on the camera or an EF lens, it makes no difference. Nothing gets converted.

If you compare it with what a focal length means on FF, the 18-55mm lens on APS-C is equivalent to a 29-88mm lens on FF. But that has nothing to do with EF or EF-S.

The only difference between EF and EF-S is that EF-S lenses are designed for a smaller image circle, contain less glass because of that.

They talk about it when comparing field of view between FF and APS-C.

Okej, thanks for the information.

I was looking for a wide angel lens, and he said me i did not needed to buy a EF lens then on my croped camera, he said i needed to buy a EF-s, or some tamron he adviced me, because there the minimum focal length was giving the same wide feeling on a croped sensor then a EF on a full frame.

But, after reading all these posts, i think i found out, that when you wanna go realy wide, only a full frame sensor can do the job and whatever lens i use, the crop sensor will only capture center parts of the image.

thanks for the help

greetings

you are welcone

the F2.8 lenses for 300 and 400 mm are very expensive.  so to use a 1.4 TC on a 200 mm F2.8  or 70-200 F2.8 is an option some consider  to spend less money, though it is no longer F2.8,  so they use for example a 1.6 7d to get the reach way out there  - 7d + 200 f2.8 + 1.4 ext = 448 FOV

You are wrong there too. There are lenses specifically designed for APS-C that go really wide too.

There is the Canon EF-S 10-22mm f3.5-4.5 USM, which goes to an equivalent of 16mm on FF... 16mm on FF is really wide!

Then there is the Sigma 8-16mm lens... It goes even wider: 8 x 1.6 = 12.8mm FF equivalent. That is super ultra wide!

If you want to go even wider, then uncorrected "fisheye" lenses are the way to go. Tokina has a 10-17mm zoom, Sigma and Samyang have special APS-C fish eye primes.

yep, and love my Toki 10-17 FE

Okej, yea, I mean, a full frame will always be possible to go wider then a croped, just because i lose the outside of my picture.

And i think 30 percent on each side is a lot, that's why i said that if you want to go realy wide, you need a full frame.

greets

By this reasoning you would get an even wider shot with a medium format camera or an 8x10 view camera.

If you only have a 24mm lens, then you will get the wides field of view by using the largest compatible format.

This means you will get a wider field of view on a full frame 5D vs. a crop factor 7D.

On the other hand, it's easier to build high quality wide angle lens for crop factor bodies.  You don't need as large an image circle, and you can recess the rear element further into the body without interfering with the mirror.

Thus if you have a limited source of money, you may be able to get wider shots with an $680 EF-S 10-22 on a 7D, then a $700 EF-17-40.

Keep in mind that the average consumer does not understand aperture, shutter speeds, or many other technical aspects of photography.  All they know is that a bigger focal length brings things "closer."   If you tell this person that a crop factor body makes his 100mm lens a 150mm lens, he will understand you.  After all, the only difference between 100mm and 150mm is how "close" they bring the subject.

The focal length of a single element lens is simply how far it needs to be from the sensor in order for an object at infinity to be in focus.   This has nothing to do with sensor size.  The aperture is the diameter of the hole expressed as a fraction of the focal length.  On a 100mm lens, f/4.0 would be 100mm/4.0 or 25mm (the "f" in f/4.0 stands for "focal length")

If you want to start talking exposure, depth of field, and other actual details of photography, then you need to realize that a 100mm lens is always a 100mm lens, regardless of the camera body.  What the sensor size does affect is "Field of View".  A 100mm f/2.8 lens on a crop body will have a similar field of view as a 150mm f/2.8 lens on a full frame.

Not true... the widest corrected lens you can buy for FF is the Sigma 12-24mm lens. The widest lens you can buy for APS-C is the Sigma 8-16mm lens. The FF equivalent of the 8mm is 12.8 mm, so both are more or less of similar width.

Also, the normal UAW lenses like the Canon 17-40mm f4 and 16-35mm f2.8 for FF are about as wide as the Canon 10-22mm  for APS-C.

So, basically, FF and APS-C go just as wide, but you have to choose the lens that gives you what you want.

FF will only go wider with the SAME lens.

Not true, see above.

Well, I want to get a fish eye, but i do not realy need the black parts in my image, so i do not need the circle vieuw