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Old Aug 3, 2008, 3:34 PM   #1
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I've been told by someone that the crop factor on the Sony Alpha 300 is 1.5x, meaning a 50mm lens on it will effectively become 75mm and a 28mm will effectively become a 50mm.

Given the fact that in film SLR's a 50mm lens is optimal for the least distortion in portraits, should I get a 28mm instead of 50mm for my Sony?

Thanks!
Kimberley
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Old Aug 3, 2008, 4:18 PM   #2
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Gardenwife wrote:
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Given the fact that in film SLR's a 50mm lens is optimal for the least distortion in portraits, should I get a 28mm instead of 50mm for my Sony?
Actually, 50mm lenses have been the kit lenses on 35mm film SLRs because they were the easiest lenses to make fast and well, and that's still the case. (When was the last time you saw a 28mm f/1.8? Sony's 35mm f/1.4 is $1,400 and their 85mm f/1.4 is $1,300, but their 50mm f/1.4 is only $350.)

And longer focal lengths are better for portraits anyway. The typical "Portrait" lens on a 35mm flim SLR was in the range of 80mm to 120mm, and had a large aperture (usually at least f/2.8.)

If you want a lens to do portraits with on an APS-C image sensor, a 50mm lens would be a much better choice than a 28mm lens.

BTW, used Minolta 50mm f/1.7 lenses are available for about $100, which is only 1/2 f-stop less than Sony's 50mm f/1.4, but $250 cheaper.
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Old Aug 3, 2008, 4:28 PM   #3
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Gardenwife wrote:
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I've been told by someone that the crop factor on the Sony Alpha 300 is 1.5x, meaning a 50mm lens on it will effectively become 75mm and a 28mm will effectively become a 50mm.
Yes, because the APS-C size image sensor is 1/3 smaller than a 35mm film exposure, a 'crop factor' of 1.5 applies. And yes, a 50mm lens has about the same angle of view as a 75mm lens on a 35mm film SLR.

But a 28mm lens has about the same angle of view as a 42mm lens on a 35mm film SLR. A 35mm lens would be closer to a 50mm lens on a 35mm film SLR, at 52.5mm.
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Old Aug 3, 2008, 9:01 PM   #4
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Okay, thanks. So, it's a fast 50mm lens I need to add to my wishlist.

When I use my 28-105mm zoom, is 50mm where I want to hover when shooting people so as not to distort their features? Or is that distortion just inherent in a zoom overall?

Taking photos inside a church gymnasium-type sanctuary today was rough. I will be so glad when I can expand my lenses to include different ones for various situations. I'm happy my husband's on board with this, saying there's no point getting cheap lenses and not having quality.

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Old Aug 3, 2008, 9:55 PM   #5
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As someone here frequently says: "Good. Fast. Cheap. Pick any two!"

There isn't a magic focal length for portraits. It's just that as the focal length gets shorter, the natural perspective will distort objects inthe center of the frame that are close to the lens.

This was taken at 45mm:



This was taken at 22mm:



Here, it makes the wedge shaped 'Vette look like a pickup truck. If it happens to a nose, that's bad.

In general, the kit lens is a good one to start with, but I think it's biggest benefit is showing the photographer what other lenses he or she needs.
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Old Aug 3, 2008, 9:58 PM   #6
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Gotcha. Those two photos illustrate your point well. Thanks.
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