# "Normal" lens for 1.6x crop factor?



## fatsheep (Jan 14, 2008)

DSLR and 35 mm SLR seem to use the same lenses yet DSLR cameras have crop factors (like 1.6x in the rebel's case).  So your "normal" 50 mm lens is going to end up being a moderate 80 mm telephoto on a DSLR right (50 * 1.6 = 80)?   

If a "normal" lens ends up being a telephoto, do you have to employ a wide-angle lens to get a "normal"?  If you have to go to wide-angle lens to get a "normal" focal length then do you have to go to a fish-eye lens to get wide-angle-like focal length?  

I'm a bit confused here... 
Explanations are more than welcome.  Thanks in advance,

- sheep


----------



## Sideburns (Jan 14, 2008)

The only problem with a 50mm becoming an 80mm is that it still has the same distortion as the 50mm.

Say you use a 35mm...that's a bit closer when cropped...but it is wider, and may make the people look fatter.  Even though you get the field of view of an almost normal lens.


----------



## Mav (Jan 14, 2008)

Yep.  On 1.5x Nikon DSLRs the 35mm f/2 is what a lot of people use for a  "normal" walkaround lens, although it was originally designed as a slight wideangle for 35mm film bodies.  The widest angle lens I've seen for Canon 1.6x DSLRs is the EF-S 10-22mm which is equivalent to 16mm on a full-frame body.  That's pretty darned wide with about a 100 degree angle of view or thereabouts.  14 or even 12mm on a full frame body will still end up being a lot wider, though.  Sigma just came out with a fisheye lens for Nikon/Canon 1.5x/1.6x bodies that will give a 160 degree horizontal field of view and a 180 degree diagonal field of view on Nikons, and just a tad less than that on Canons.  But you're correct in your idea that you could also use a full frame 15/16mm fisheye on a crop body, but it won't be as wide as the fisheyes that are designed for crop bodies.  Not sure which would be wider, a 15/16mm fisheye on a crop body, or a 10mm rectilinear lens.  The angle of view formulas that apply to rectilinear lenses don't apply to fisheyes.  I'm sure if you Google around that somebody has tried it and you might be able to figure it out.  BTW I think Canon also has a 28mm f/2.8 prime lens that might give a bit more normal view on a 1.6x body, but it's not quite as quick as the 35mm f/2.


----------



## Ls3D (Jan 14, 2008)

In a related thought, does the 1.6 conversion factor apply to cannon's EFS lenses?

-S


----------



## Josh66 (Jan 14, 2008)

Ls3D said:


> In a related thought, does the 1.6 conversion factor apply to cannon's EFS lenses?
> 
> -S



I've always wondered about that too.  Since they know it's going on a crop body, is 18-55 really 18-55, or is it 28-85?


----------



## Peanuts (Jan 14, 2008)

I imagine an 18-55mm is perceived to be a 28-85mm.  I can't imagine the confusion they would introduce by stating the 'real' focal length.


----------



## omardxb (Jan 15, 2008)

Interesting enquiry and comments, it's true, the 18-55mm is actually a 28-85 lens, but for easiness sake (And marketing purposes probably) 
they still call them 18-55


----------



## ghpham (Jan 15, 2008)

hhmm...interesting discussion.  The thing that's really confusing to me is the crop factor.  Does it really mean "telephoto" or is it because the pictures got cropped, that it actually give you the feel of "telephoto" over the 35mm frame?


----------



## Mav (Jan 15, 2008)

The focal length of the lens is the focal length of the lens, which never changes.  The only thing that changes is the angle of view, which varies depending on the sensor size.  A bigger sensor will see wider.  Hence to get the same angle of view as 28mm on a full-frame digital or 35mm film, you need an 18mm lens on a 1.6x cropped DSLR to make up for the smaller sensor that doesn't see as wide.


----------



## jstuedle (Jan 15, 2008)

omardxb said:


> Interesting enquiry and comments, it's true, the 18-55mm is actually a 28-85 lens, but for easiness sake (And marketing purposes probably)
> they still call them 18-55




They are marked what they are. A 18-55mm lens is a 18-55 focal length no matter the crop factor. The crop factor makes it "look" like a 28-85 as compared to the full frame 35mm film or sensor camera. It's strictly a "field of view" issue. It's no marketing, it is what it is. (no I'm starting to sound like Bill Clinton, gotta work on that) Look at your point and shoot camera. It might have a lens marked 4mm-13.5mm that looks like a 35-115mm lens on a full frame 35mm camera. They just have a similar field of view, but the P&S does in fact have a 4-13.5mm lens.


----------



## Tighearnach (Jan 15, 2008)

Now im confused!

An 18-55mm EF-S lens for Canon is 18-55 yes but it is made specifically for a cropped sensor camera therefore it wont work on a full frame camera therefore it is not really 18-55 but  28-88....?????

Yes? No?


----------



## Big Mike (Jan 15, 2008)

> An 18-55mm EF-S lens for Canon is 18-55 yes but it is made specifically for a cropped sensor camera therefore it wont work on a full frame camera therefore it is not really 18-55 but 28-88....?????
> 
> Yes? No?


NO
Mav and jstuedle are correct.  The focal length listed on the lens is the actual focal length.  If it says 18-55mm, then that is the actual focal length.

Look at the EF 17-40mm lens, for example.  It will fit both full frame (or 35mm film) and 'crop factor' cameras.  The field of view (FOV) will be different though, depending on the camera it's mounted on.  So it's not the lens that's different, it's the camera.

The same thing applies of EF-S lenses.  They aren't any different...18mm is still a very short focal length...but because the camera 'crops' the image, the FOV is narrower than it would be on a full frame camera.

EF-S lenses are actually different from EF lenses.  They will only be used on crop cameras, so they don't need as big of an image circle.  Also, the rear element protrudes farther into the camera body, which is the main reason you can't/don't use them on full frame bodies....because the rear element would interfere with the movement of the mirror.

Just to say it again.  The crop factor is a function of the camera...not the lens.


----------



## fatsheep (Jan 15, 2008)

This makes more sense now.  A 50 mm lens will have less FOV on a crop factor camera than on a 35 mm but the image has the same distortion properties.  So a fish-eye lens will still have the same distortion, just less FOV on a crop factor camera.  

Thanks for the explanations,

- sheep


----------



## Big Mike (Jan 15, 2008)

> So a fish-eye lens will still have the same distortion, just less FOV on a crop factor camera.


That's correct.  
However, remember that with a fish-eye...there is more distortion at the edges than in the middle...so while you do get that distorted look...a fair amount of it will be cropped off of the edges (when using a full frame fish-eye on a crop body).


----------



## fatsheep (Jan 15, 2008)

Big Mike said:


> That's correct.
> However, remember that with a fish-eye...there is more distortion at the edges than in the middle...so while you do get that distorted look...a fair amount of it will be cropped off of the edges (when using a full frame fish-eye on a crop body).



Ack...  I'm not going to be buying a fish-eye lens in the near future but that doesn't sound too great for DSLR users.  I've heard of full frame DSLRs but they are usually extremely expensive right?


----------



## Big Mike (Jan 15, 2008)

> Ack... I'm not going to be buying a fish-eye lens in the near future but that doesn't sound too great for DSLR users.


I've heard about a fish-eye lens that is 8mm or something like that...which would probably be for crop bodies.  



> I've heard of full frame DSLRs but they are usually extremely expensive right?


There were a few older ones from Kodak, but let's not mention them.  Right now, there is the Canon 5D (fairly expensive) and the Canon 1Ds mk II and the 1Ds mk III (very very expensive).
There is also the new Nikon D3, which is also very expensive.


----------



## Mav (Jan 15, 2008)

fatsheep said:


> Ack...  I'm not going to be buying a fish-eye lens in the near future but that doesn't sound too great for DSLR users.  I've heard of full frame DSLRs but they are usually extremely expensive right?


http://www.sigmaphoto.com/lenses/lenses_all_details.asp?id=3337&navigator=6

http://www.bhphotovideo.com/c/product/535763-USA/Sigma_477_101_10mm_f_2_8_EX_DC.html

$649 seems like a good price.  I suspect this will be a hot item for Canon 1.6x DSLR owners since this is the first fisheye being made for those bodies.  Nikon's 10.5mm DX body fisheye came out in 2003 so most people who want one have one.  I have this lens and love it.  It's great for all sorts of things, and with the various software out there you can leave it full-fish or do a full rectilinear conversion or anything in between.


----------



## fatsheep (Jan 15, 2008)

Mav said:


> http://www.sigmaphoto.com/lenses/lenses_all_details.asp?id=3337&navigator=6
> 
> http://www.bhphotovideo.com/c/product/535763-USA/Sigma_477_101_10mm_f_2_8_EX_DC.html
> 
> $649 seems like a good price.  I suspect this will be a hot item for Canon 1.6x DSLR owners since this is the first fisheye being made for those bodies.  Nikon's 10.5mm DX body fisheye came out in 2003 so most people who want one have one.  I have this lens and love it.  It's great for all sorts of things, and with the various software out there you can leave it full-fish or do a full rectilinear conversion or anything in between.






fatsheep said:


> Ack... I'm *not* going to be buying a fish-eye lens in the near future but that doesn't sound too great for DSLR users. I've heard of full frame DSLRs but they are usually extremely expensive right?



  One word makes all the difference doesn't it?   I've done that many times before though so don't worry about it.  I'll make a note of the lens you recommended though.


----------



## dipstick (Jan 15, 2008)

It's about time we get a sticky about the big focal length confusion on crop cameras. People seems to be confusing the field of view with focal length. It is not only a problem among beginners, I even tried to explain this to professional photographers that doesn't seem to have a clue.

What I don't get though is why the confusion is so massive nowadays. For those of us who have been shooting film, we always knew that a 50mm would give a different angle of view on a 6x6 then on a 35mm camera. 

Instead of saying "this 18mm is really a 28mm", we should say "this 18mm lens  on a cropped sensor camera will give you the same field of view as a 28mm lens on a 35mm camera.

The strange thing though is that a lot of people haven't been using anything else than crop cameras, and they are still confused about the "real" focal length. Why bother unless you shoot two different formats? 

It is what it is...


----------



## fatsheep (Jan 15, 2008)

dipstick said:


> It's about time we get a sticky about the big focal length confusion on crop cameras...



I'd agree, a general beginner's sticky would be a good idea.  It could cover the issue discussed here as well as basics: exposure, shutter speed, aperture, ISO, depth of field, etc...  Then maybe a section about common problems and such. 

I'd be willing to write up a little explanation of exposure (shutter speed, aperture, and ISO) for the sticky.


----------



## Big Mike (Jan 16, 2008)

People rarely read stickies anyway.

All of these topics have been discussed many, many times before...all someone needs to do, is use the search function.


----------



## fatsheep (Jan 16, 2008)

Big Mike said:


> People rarely read stickies anyway.
> 
> All of these topics have been discussed many, many times before...all someone needs to do, is use the search function.



Sure, searching the forum works but the information is going to be spread out over many different topics.   We could make that search a lot faster by just making a sticky.  People could contribute to the sticky and revise to make it up to date, accurate, and easy to read.  Basic questions could be referred to the sticky instead of answered individually.  That would make things easier for the novice (as well as the people answering questions) in my opinion.


----------



## Josh66 (Jan 16, 2008)

What exactly is the difference between EF and EF-S lenses? They look the same to me.  The mount doesn't appear to be physically different...


----------



## Sideburns (Jan 17, 2008)

dipstick said:


> It's about time we get a sticky about the big focal length confusion on crop cameras. People seems to be confusing the field of view with focal length. It is not only a problem among beginners, I even tried to explain this to professional photographers that doesn't seem to have a clue.
> 
> What I don't get though is why the confusion is so massive nowadays. For those of us who have been shooting film, we always knew that a 50mm would give a different angle of view on a 6x6 then on a 35mm camera.
> 
> ...



I agree.  Unless you shoot both film/FF and digital/crop...then why does it matter...you don't know the difference anyway.



O|||||||O said:


> What exactly is the difference between EF and EF-S lenses? They look the same to me.  The mount doesn't appear to be physically different...



The back lens is closer to the sensor...it's smaller in diameter...and they're cheaper to make.


----------



## AmericanJesus (Jan 17, 2008)

Whats it meant by 1.6 crop factor?


----------



## Mav (Jan 17, 2008)

http://www.google.com/search?source=ig&hl=en&rlz=&q=crop+factor


----------



## Big Mike (Jan 17, 2008)

http://www.thephotoforum.com/forum/search.php?searchid=1061433


----------



## yeti (Jan 17, 2008)

O|||||||O said:


> What exactly is the difference between EF and EF-S lenses? They look the same to me. The mount doesn't appear to be physically different...


 
It was already mentioned that EF lenses have a wider image zone than the EF-S ones. It was also mentioned that EF-S lenses protrude a bit further into the camera.

I would like to contribute the following:

Wide-angle lens have to collect light from a very wide angle and then produce an image on a sensor or film of a fixed size. With a mirror moving back and forth you have to leave some space before the film/sensor for it. This is typically very hard to do and requires lots of expensive elements to collect light from so large an angle, bend it in all sorts of ways and then make it produce an image of certain size, distance and quality into the camera.

If you get closer to the film/sensor, however, you can shorten the focus distance of your lens, which means you don't need to bend light so much anymore to produce an image on your film/sensor. This translates into fewer and cheaper elements for your wide-angle lens, which translates into lower production costs for a good-quality lens, which finally directly translates into more $$$ in your pocket and happier parents/spouse. 

On film cameras there is so much you can do: you can't ask the world to change the film they use, and if you did, quality would suffer. Your film is 35mm, therefore your mirror has to be approximately 35mm as well. Well 35mm is 35mm and requires so much space to swing and that's that. With a digital cameras things are different: your CCD is as big or as small as you can make it (and still have customers buying your cameras). So, Canon, seeing that a 35mm CCD is currently so incredibly expensive to make (I assume because of all the noise it picks up and the purity of the silicon required), decided to do something about it and have two problems solve each other.

Telephoto lens are fine with EF: the larger the distance to produce image, the better as they tend to bend light THE OTHER WAY. Having them as EF-S is silly. Instead all Canon has to do is make sure EF-S and EF mounts compatible (read physically and electrically the same) and your telephoto lens would work just fine without being specially crafted for EF-S. However wide-angle lens, which benefit from cropped-sensor cameras, are cheaper as EF-S than they would be if they were EF. The same goes for the cameras that use them.

The bottom line is that EF-S is basically a way to cut production costs for both your lens and your camera, with the tradeoff that your not-so-expensive-lens-anymore will only work on your not-so-expensive-camera-anymore (or your camera's mirror will crash into the lens as it swings and your expensive camera would be ruined).

That's my take on things. Correct me if I am wrong. I hope it helps.


----------

