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Old Sep 18, 2003, 7:56 AM   #11
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Yeah, I saw that 300-800 on eBay. I guess it goes for around $2200 on there new.

That 50-500mm sigma was pretty nice I do say. But I wanted to play around with the big fstop. Never had a f/2.8 The lowest Ive owned so far is a f/4. Im sure Ill be pleased with it. I hope :?
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Old Sep 18, 2003, 11:22 AM   #12
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Wow $2,200 NEW???? That is hard to believe. Gotta be a scam. That lens is twice that at reputable places.

I'd love to get a long f4 lens. I have the 50mm f1.8. That fstop sure comes in handy. But my only choice at f4 is the 500mm or 600mm (I guess sigma makes a f4.5 500mm.) Those are very expensive (more than that 300-800) and the 500 isn't much more reach than what I have now.

Difficult choice, especially at those prices.

But the reality is that I need to do more shooting in more locations. I need to learn how I shoot. I so often go to places where you are on walkways surounded by water. Where it is just imposible to get closer, so longer lenses are the only answer. Period. I need to spend some time in other places and see if an 80-200 f2.8 with TC or 300 f2.8 wouldn't be a better, lighter, cheaper choice.

Eric
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Old Sep 18, 2003, 2:17 PM   #13
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with regret the history on the sigma 17-35 has a history of softness. the sigma 70-200 is an excellent lens though for the $$$
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Old Sep 18, 2003, 8:29 PM   #14
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wow, dont I feel like a newbie cameraman... :roll: :?

I finally found out what DOF really does with different fstops. The bigger the fstop ie: 2.8 the more blurred for/background is which what I wanted 8) I totally got it backwards. Yeah I want the background to be blurred as much as possible.

But questions are now:

1. Bigger fstops 1.4-2.8, etc seem to focus very fast? Is that
just me or is something going on I dont understand? The only
thing I can think of is the amount of light that enters the lens
the large fstop helps the camera AF?

2. If a large stop makes for/backgrounds blurry, what about say like
animal shots of there face? Is it going to blur details ie: wiskers, ears
etc? Or do I just use a smaller fstop?

Man, if I fully understood this stuff (I felt pretty sure I knew what DOF was and how it was effected by fstops)... I may have bought a different lens... but its all part of learning and now I know its completely backwards from what I thought it was. Man I luv photography.
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Old Sep 18, 2003, 10:36 PM   #15
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oh, depending on the lighting, apeture, and the lens, wides have greater DOF and longs less so, you could have the front end of the head in focus and the back end of the head out of focus. yeah photography is cool.
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Old Sep 18, 2003, 10:42 PM   #16
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It is possible that with more light it will focus faster. I believe that the 10D uses a contrast detection system for AF (anyone?). If you don't have enough light, it will have trouble detecting contrast. Maybe the opposite is true; if you have a lot of light contrast differences get easier to detect and it lockes into focus faster. Obviously it isn't "faster" in the sense that the motor is not working faster. It's that it detects the contrast faster and stops trying to focus (no hunting.)

Taking pictures of animals with large apertures (low fstops) is difficult because parts of the animal will be in focus and parts won't. It's difficult. Add into it that the smaller aperture (larger fstop) means less light... but larger DOF. So you need lots of light, and a reasonable fstop (f8 or so.... maybe more.) And, of course, if the animal is moving, you need a high shutter speed. This is just part of the reason why taking pictures of animals hard. You really need to focus on the eyes/head... but you want the rest in focus too.

This is something I have not mastered yet.

Most 35mm lenses are also better when stopped down a bit. Not when you shoot wide open (small fstop.) So another thing you get is that f4.5 on a f2.8 lens will probably be better (all other things being equal) than f 4.5 on an f4.5 lens.

Eric
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Old Sep 19, 2003, 12:32 AM   #17
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The range of the DOF in which the picture is still considered sharp, is dependent on the focal length and the distance to the subject, as well as the f-stop. The higher the focal lenght, the shallower the DOF. The closer the subject, the shallower the DOF. The higher f-stop (lower number) the shallower the DOF. Thus there are three factors that come into play with DOF. Personally I think that is cool, but it takes time to learn and master.

Play with the DOF calculator at http://www.photozone.de/bindex3.html (bottom of the page). It can give you a good feel about what would be in focus, or not.

Barthold
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