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DPChallenge Forums >> Hardware and Software >> Whats the actual size of 17-40L on an APS-C sensor
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Showing posts 1 - 13 of 13, (reverse)
AuthorThread
 05/30/2008 12:47:51 PM · #1
The canon 10-22mm on an APS-C is 10-22mm, so what would the actual size of a canon 17-40mm be on an APS-C sensor like the rebel xt?
 05/30/2008 12:54:29 PM · #2
always multiple the given mm by 1.6

10-22 is actually 16-35

17-40 is 27-64
 05/30/2008 12:59:00 PM · #3
Bad terminology: the "actual" size is 17-40mm. The equivalent focal length for both lenses sre as Hopper states them; multiply by 1.6 for APS-C sensors.

R.

Message edited by author 2008-05-30 12:59:55.
 05/30/2008 01:01:59 PM · #4
The focal lengths of the EF-S lenses and the "made for digital" lenses but other manufacturers get multiplied by 1.6 like the EF lenses when talking about APS-C sensors on the Canon bodies ;)

-dave
 05/30/2008 01:03:33 PM · #5
is'nt the 10-22 lens designed for and aps-c sensor? Hence should'nt it be actually 10-22 on an aps-c sensor?
 05/30/2008 01:07:06 PM · #6
Originally posted by dmadden:
is'nt the 10-22 lens designed for and aps-c sensor? Hence should'nt it be actually 10-22 on an aps-c sensor?


This is a common misconception. The lens focal length is 10-22, regardless of what camera it is on or designed for. On an APS-C sensor, the range is effectively 16-35.
 05/30/2008 01:07:43 PM · #7
Originally posted by dmadden:
is'nt the 10-22 lens designed for and aps-c sensor? Hence should'nt it be actually 10-22 on an aps-c sensor?


You would think that but they still use the 35mm equivalent even on their ef-s lenses.
 05/30/2008 01:07:43 PM · #8
"made for digital sensors" just means the diameter of the glass doesn't have to be as large. Film lenses used on a digital sensor (non full frame digital sensors) have wasted glass, so to speak. Think of a rectangle inside of a circle. For digital lenses, the rectangle fits just inside the circle, for film lenses - the circle is larger than the rectangle.

clear as mud
 05/30/2008 01:13:37 PM · #9
So technically a 17-40mm could be a step up from a 10-22 on an aps-c sensor. In other words i wouldnt be duplicating the range on the 10-22, not sure if that makes sense.

Bear with me, i'm a little slow :)
 05/30/2008 01:19:09 PM · #10
correct: 10-22mm and 17-40mm only overlap from 17-22mm


05/30/2008 01:19:46 PM · #11
Originally posted by hopper:
"made for digital sensors" just means the diameter of the glass doesn't have to be as large. Film lenses used on a digital sensor (non full frame digital sensors) have wasted glass, so to speak. Think of a rectangle inside of a circle. For digital lenses, the rectangle fits just inside the circle, for film lenses - the circle is larger than the rectangle.

clear as mud


this makes it a lot clearer. My mind was getting to that stage, like when u try to imagine there is absolutely nothing that exist's. Even nothing :)
 05/30/2008 01:29:02 PM · #12
The focal length of a lens is defined by the lens design itself. It's totally independent of the camera.

When people talk about "equivalent" focal lengths, they mean that a lens placed on an APS-C camera has the equivalent field of view of a longer lens on a 35mm camera.

Look at the lens on your itty bitty PnS camera, the focal length probably starts at about 4.5 mm or so. OTOH for a 4x5 view camera, a 180mm gives the same image as a 50mm lens on a 5D.
 05/30/2008 03:08:38 PM · #13
The thing that really confuses the issue is that some P&S cams actually list the 35mm equivalent instead of the actual focal length on the lens itself. Pretty much *all* the P&S cams use the 35mm equivalent focal length information on their marketing info, but few of them state that it is "equivalent."

Example: My Nikon Coolpix 995 has an 8-32mm lens, which has a 28mm to 112mm equivalent field of view in 35mm terms. But the lens is marked as 8-32mm. But as I recall the marketing materials did mention the equivalents.
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