# Digital SLR question



## thebeginning (Apr 7, 2005)

I have been wondering this for quite a while...when you get a 17mm lens (say 17-55 or so) how come it doesnt seem to really be 17mm?  I mean, on my film camera, my 28mm lens is more wide angled than the 17mm.  Why is this? and can you get ultra wide angle lenses for dSLRs or do you have to just get a .45x adapter or something?


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## Unimaxium (Apr 7, 2005)

I hope this answers your question...  With most digital cameras (except for really high end ones like the Canon 1Ds MKII), the digital sensor is smaller than a standard 35mm frame. In fact, most are the size of an APS frame. Because of this, there is a cropping effect which makes the lens effectively longer than it would be on a film camera. Most DSLRs tend to have a magnification factor of 1.6 or 1.7, so a 17mm would end up being like a 28mm and a 28mm would be about a 45mm.


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## thebeginning (Apr 7, 2005)

oh. that's a bummer. 

so would a 200mm lens be like a 300mm and a 300 would be like a 510? hey, im kind of liking that


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## walter23 (Apr 8, 2005)

thebeginning said:
			
		

> oh. that's a bummer.
> 
> so would a 200mm lens be like a 300mm and a 300 would be like a 510? hey, im kind of liking that




Yeah, exactly.  You gain some length at the telephoto end of things but lose out if you want ultra-wide or fisheye.  Some manufacturers are making ultra-wide lenses for digital now - or at least Canon is.  There's an EF-S 10-22mm (which is about a 16-35mm in 35mm equivalent) for digital only.  It's way too expensive in my opinion, but I suspect there will be more lenses like this around in the future.

There are 35mm-sized sensors in some high-end cameras that remove this issue (e.g. the ~$9000 canon 1ds mkII).


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## catweh00 (Apr 8, 2005)

Yeah, nikon and sigma are making some wide angle lenses now too.  I own the nikon d70, and the kit lens has an 18mm rating (around 27mm or so standard SLR), and I cannot complain.  I love their DX sensor, or whatever its called.  I like the idea of the smaller sensor size and the 1.5x crop factor.  For my 300mm, its now a 450mm lens.  Also, if I add I teleconverter to that, its now a 630mm lens.  

True, it does suck if you need a wide angle lens, but I love getting more out of camera in terms of tele capability.  And I rarely would need anything wider than the kit lens.  

I enjoy it, thats all I can say.
Craig


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## Artemis (Apr 8, 2005)

The reason the sensors are smaller is because unlike film, digital cant handle the bits at the side as they become blurry and out of focus, and thats why the dfs lenses are flat, because with a curved lens the light strikes the sensor of film on the side and thats where the bluryness comes from


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## bobbyandrews (Apr 8, 2005)

Artemis said:
			
		

> The reason the sensors are smaller is because unlike film, digital cant handle the bits at the side as they become blurry and out of focus, and thats why the dfs lenses are flat, because with a curved lens the light strikes the sensor of film on the side and thats where the bluryness comes from




Im sure thats  not the reason. the 1ds mkii has a fulll frame sensor and the images are not out of focus at the sides.  Or are they??


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## Big Mike (Apr 8, 2005)

Artemis said:
			
		

> The reason the sensors are smaller is because unlike film, digital cant handle the bits at the side as they become blurry and out of focus, and thats why the dfs lenses are flat, because with a curved lens the light strikes the sensor of film on the side and thats where the bluryness comes from



This sounds a little fishy to me...but I'm no expert :roll:

I've always heard that the large sensors cost more...and that's the main reason that a 1Ds Mark II is $8000 and a Rebel XT is $900.  (Well, it's a different, more complicated sensor as well).  When the first APS sized sensor DSLR cameras came out...a lot of us thought that cheap full frame DSLRs were just around the corner...after all, if they mass produced the chips, wouldn't they be cheaper?  Maybe it would be...but the Camera companies are happy to have created a whole new market segment...complete with it's own new style of lenses.  Who knows...


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