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Old Feb 19, 2005, 3:25 PM   #1
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I'm ready to take the digital plunge! I'm a littleconfused about the 1.5x focal length on the DSLRs I've been researching. Could someone tell me how this works? Are images "cropped" when looking through the lens of a DSLR? Thanks for your help!


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Old Feb 19, 2005, 5:54 PM   #2
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The sensor on most DLSRs is smaller than 35mm film. This means that any given shot through a DLSR will cover a smaller area than the corresponding shot taken with the same lens and settings on a 35mm camera. The optics on the DSLRs is designed for this so you still see around 95% of the image that will appear in the final shot.
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Old Feb 19, 2005, 6:34 PM   #3
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The 1.5 (or 1.6 in some Canon cameras) crop acts like zoom. A 50mm lens acts like a 75mm (or 80mm in the 1.6 crop cameras) vs 50mm in a 35mm film or full frame digital camera. This is a plus in the telephoto range and a problem shooting wide angle shots.
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Old Feb 19, 2005, 7:11 PM   #4
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Imagine if you had a 1.5x teleconverter permanently stuck on a film SLR. Then all of your wide angle lenses would not cover as wide a field of view. Your 28mm lens would become the equivalent of 42mm and your 50mm 'Normal' lens would be closer to a 75mm 'portrait' lens.

Sure you would feel good that your 200mm tele is now 300mm so, what you lose on wide angle you gain on the tele end.

This is not different from the difference between Medium format and 35mm. In Medium format a 'normal' lens is closer to 80mm while in 35mm a 'normal' lens is 50mm and on a dSLR a 'normal' lens is closer to 35mm.
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Old Feb 19, 2005, 7:56 PM   #5
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Thanks for explaining! I understand the conversion now. Is there a way to get a "true" wide angle shot on a DSLR? My widest lens is 24mm... I may have to go wider?

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Old Feb 19, 2005, 8:20 PM   #6
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If you want to achieve the same field of view as your 24mm lens then you had better start saving for a 15mm fisheye. Canon has a nice one for only $580
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Old Feb 19, 2005, 8:34 PM   #7
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Ouch! That's what I thought----have to get a fish-eye. On the other hand, I could probably still use my film SLR in those cases...

Thanks!
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Old Feb 20, 2005, 5:43 PM   #8
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Ther other thing to check in to is "digital SLR only" lenses - they're smaller and lighter because of the smaller focal length, and they can have nice wide ends without a huge price tag. As an example, look at the new Sigma lenses at PMA:

http://www.dpreview.com/articles/pma2005/Sigma/

One is 10-20mm F/4.0-5.6 - equivalent to 15-30mm on a 35mm SLR; the zoom lens (look at how small it is!) is 18-200mm (27-300mm equivalent). Yes, it's a Sigma, but the point is, these "digital only" lenses will fill that wide-end gap for dSLRs nicely; as dSLR's become more popular, more of the manufacturers are starting to produce similar lenses for their cameras. I know Pentax is on board, as is Olympus; I think Nikon is planning to introduce something like these lenses as "kit" lenses with their upcoming (?) D50. Take a close look at the pictures of the new Canon XT350 - that kit lens is 18-55mm; with 1.6X focal length, it's equivalent to 29-88mm - not a bad general lens.

I think it's nice that the manufacturers are trying to make the "old" film SLR lenses work with their new digital cameras, but really, they're doing this so that their customers that have already invested in "big glass" aren't left out - or discouraged from upgrading.

If you're not heavily invested in film SLR lenses, you could look at the digital lenses instead for the size and weight savings. Downside, of course, is that you don't know what will happen in a few years; perhaps sensors are going to grow back to 35mm size - and then your digital lenses will be worthless..... OTOH, someone could invent a keyfob cam with infinite resolution and perfect color, and then ALL of this stuff would be obsolete!

ECM
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Old Feb 21, 2005, 7:21 PM   #9
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ecm--good info! Thanks! I hadn't even considered digital lenses. My current wide angle, is not my "best" lens (read: cheapest!), so I wouldn't be out a whole lot when it comes to replacing it. And, lucky for me, my film SLR is a Pentax and I'm planning to get the *istDS.

Thanks again!
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