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Sharp Focus

Tue May 26, 2009 12:13 pm

I need help.

I use a canon 350d with sigma 70-300mm lens. I just don't seem to get sharp focus. I use 5.6 aperture mostly at telephoto range. Manual focus and auto focus seem more or less the same.
I try to get shots of planes passing over my house. Obviously I use no tripod for this. Can anybody give me some pointers?

Thank you
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RE: Sharp Focus

Tue May 26, 2009 12:26 pm

use aperture 8-11 and auto focus and the problem is solved

[Edited 2009-05-26 06:02:53]
A boy learn's much more at the airport then he do at school
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RE: Sharp Focus

Tue May 26, 2009 12:37 pm

Getting good pics of planes passing is hard, and that Sigma is rather soft at 300mm which also affects your images. As Othic said, keep the aperture at 8-11. And it's also hard to keep that small dot that the aircraft is, in the focus point (use center focus point only). I find it a little easier to hunt the contrail just behind the aircraft. And shoot series, odds are one is good if you shoot a series of 6-8 shots. Crew-Head Support
5D Mark III, 7D, 17-40 F4 L, 70-200 F2.8 L IS, EF 1.4x II, EF 2x III, SPEEDLITE 600EX-RT
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RE: Sharp Focus

Tue May 26, 2009 3:31 pm

Especially relatively cheap lenses are best at medium apertures of 8-11, 5.6 is completely open aperture, I guess, just forget about that if it's not a really good, which sadly means really expensive lens.
Another idea: Is your lens maybe dirty or scratched? Or maybe dropped the camera, so the focussing is maladjusted (don't know if this is the correct word, but you might know what I mean).


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RE: Sharp Focus

Tue May 26, 2009 3:56 pm

I totally agree, I have the Sigma 55-200 and it is the sharpest in the area of f/8-f/11, I liked the Sigma so well that I recently bought the 28-105, very good medium range zoom, great walkaround.
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RE: Sharp Focus

Wed May 27, 2009 12:37 am

From my experience the budget Sigma 70-300 is a particularly soft lens, especially above about 200mm. Closing the aperture down (making sure to shoot in Av mode) to F8 or smaller (higher as the numbers go) as others have said will improve things but if you want super-sharp images you're going to have to invest in better glass (I'm afraid!).

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RE: Sharp Focus

Wed May 27, 2009 1:46 am

When I was starting out I too was wondering why the images from my 100-400 f/4.5-5.6 Canon lens would come out soft. It's a professional series lens and I was dumbfounded at the results I was getting.


I realized I was gripping the lens at the focus ring! On this lens even if you have it set to autofocus the ring will still adjust the focus. So when I'd pan or zoom in or out (it's a telescoping lens) I would bump the focus off enough to create a less than sharp image. Once I started holding it properly (not on the focus ring) I was able to get amazingly sharp images out of it....

So, you might want to see if maybe you're running into a similar situation.

And yes, I'm embarrassed by this.
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RE: Sharp Focus

Wed May 27, 2009 2:57 am

Actually that is a good point not to touch the focus ring. Along those lines, keep a steady hand. I'm at fault often slightly moving the camera when I shoot!
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