Which lens for my Sony a200

audiobomber

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Another inherent drawback of Sony cameras that effects Sony's (and others) market share, is in-body image stabilization and it's associated limitations when compared to in-the-lens image stabilization.

You keep saying this, do you have any evidence? Any review I've ever read lists in-body stabilization as a pro, not a con.
1. In-the lens IS can be seen working in the camera viewfinder, so the photographer can know when the image is stable and can release the shutter. In the body IS cannot be seen in the viewfinder.

2. In-the-lens IS can correct for larger movements than can in-the-body IS.

I agree with those, but you do get an indicator that says the stabilizer is ready. In-body works for every lens and you only pay once. That's more important to me.

I just received a Sigma 150-500mm with OS. I should do some testing vs in-body on my K20D. The K-5 would be a better test, because it corrects for rotational motion, which the K20 and in-lens systems don't.
 

AUZambo

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The OP has a Sony crop sensor, so divide everything by 1.5.
Actually, you MULTIPLY by 1.5. :p

It depends on which way you're converting. You divide by 1.5 to convert from 35mm focal length to cropped. The suggested portrait lens was a 70-200mm f2.8. The equivalent focal length for a 1.5X crop sensor would be a 46-135mm lens. Sigma has a 50-150 f2.8 for A-mount.

The traditionally recommended FL for portrait is 85mm, which translates to a 56mm lens on a 1.5X sensor.
I'm 90% sure you have it backwards, unless I'm just misunderstanding you. The focal length designation on the lenses and boxes indicates the focal length if used on a 35mm camera. Since the sensor in most DSLRs is smaller than a 35mm frame, the camera essentially crops the image, ignoring the outer parts that would have been captured on a 35mm or full frame DSLR. Since you are cropping it, it's as if you're zooming in a tad bit....so a 70-200 mm lens would act like a 112.5-300 mm on a sensor with a 1.5x crop factor.
 

table1349

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Actually, you MULTIPLY by 1.5. :p

It depends on which way you're converting. You divide by 1.5 to convert from 35mm focal length to cropped. The suggested portrait lens was a 70-200mm f2.8. The equivalent focal length for a 1.5X crop sensor would be a 46-135mm lens. Sigma has a 50-150 f2.8 for A-mount.

The traditionally recommended FL for portrait is 85mm, which translates to a 56mm lens on a 1.5X sensor.
I'm 90% sure you have it backwards, unless I'm just misunderstanding you. The focal length designation on the lenses and boxes indicates the focal length if used on a 35mm camera. Since the sensor in most DSLRs is smaller than a 35mm frame, the camera essentially crops the image, ignoring the outer parts that would have been captured on a 35mm or full frame DSLR. Since you are cropping it, it's as if you're zooming in a tad bit....so a 70-200 mm lens would act like a 112.5-300 mm on a sensor with a 1.5x crop factor.


Focal length is Focal length. Physics and characteristics of a lens do not change because of sensor size. A 50mm lens is a 50mm lens no matter what body you have it on. You are confusing crop with magnification of focal length. They are not the same thing.
Understanding Camera Lenses
DSLR Magnification
 

audiobomber

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Actually, you MULTIPLY by 1.5. :p

It depends on which way you're converting. You divide by 1.5 to convert from 35mm focal length to cropped. The suggested portrait lens was a 70-200mm f2.8. The equivalent focal length for a 1.5X crop sensor would be a 46-135mm lens. Sigma has a 50-150 f2.8 for A-mount.

The traditionally recommended FL for portrait is 85mm, which translates to a 56mm lens on a 1.5X sensor.
I'm 90% sure you have it backwards, unless I'm just misunderstanding you. The focal length designation on the lenses and boxes indicates the focal length if used on a 35mm camera. Since the sensor in most DSLRs is smaller than a 35mm frame, the camera essentially crops the image, ignoring the outer parts that would have been captured on a 35mm or full frame DSLR. Since you are cropping it, it's as if you're zooming in a tad bit....so a 70-200 mm lens would act like a 112.5-300 mm on a sensor with a 1.5x crop factor.

What I said is exactly correct. You're trying to go the other way and state what a 70-200mm lens would look like on a cropped sensor, but that's not what we're after. If you have a full-frame camera, you would use a 70-200mm 2.8 as an ideal portrait zoom range. If you use that lens on a cropped camera, it will be slightly too long. A Sigma 50-150 f2.8 would provide the (roughly) equivalent FOV on the OP's Sony.
 
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AUZambo

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It depends on which way you're converting. You divide by 1.5 to convert from 35mm focal length to cropped. The suggested portrait lens was a 70-200mm f2.8. The equivalent focal length for a 1.5X crop sensor would be a 46-135mm lens. Sigma has a 50-150 f2.8 for A-mount.

The traditionally recommended FL for portrait is 85mm, which translates to a 56mm lens on a 1.5X sensor.
I'm 90% sure you have it backwards, unless I'm just misunderstanding you. The focal length designation on the lenses and boxes indicates the focal length if used on a 35mm camera. Since the sensor in most DSLRs is smaller than a 35mm frame, the camera essentially crops the image, ignoring the outer parts that would have been captured on a 35mm or full frame DSLR. Since you are cropping it, it's as if you're zooming in a tad bit....so a 70-200 mm lens would act like a 112.5-300 mm on a sensor with a 1.5x crop factor.


Focal length is Focal length. Physics and characteristics of a lens do not change because of sensor size. A 50mm lens is a 50mm lens no matter what body you have it on. You are confusing crop with magnification of focal length. They are not the same thing.
Understanding Camera Lenses
DSLR Magnification
Thank you for correcting me. The second link you provided is exactly what I was trying to say...I just wasn't saying it correctly.
 
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