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05-22-2010, 09:51 AM   #1
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300mm f 2.8 sigma apo dg.

I have had a time with this lens. I need your input one more time. I appreciate all the help before.

You guys that have this lens?

I can get good results at 2.8 close up. No problem. But i mean really close 10-15ft. Then the image starts getting unusable.
It is better at f3.2. Even better at 3.5 and sharp at f4 and above until it starts dropping off at higher f stops.
My problem is i shoot birds in the jungle. I want the big glas for a light bucket and the fast 2.8 for usable shots. I cannot get it with this lens. If shooting over 10-15 feet. Even in good light it is very bad at f2.8. Better at f3.2 to f4.

My thought is buying fast glass should be usable at the lower f stop.. f2.8.

I reliaze the DOF changes alot. But the farther away you are the greater the depth of field. The good thing is closer at 2.8 the auto focus will give good results. With good light it is a snap. But close the DOF is very shollow.

At 2.8-f3.5 I cannot get usable images when croping at 50- 100 percent. It is very bad.

Also I bought the 1.4 and 2.0 converters with the lens. They follow the lens design to a tee. Same results but with farther usable points 1.4T.C. say 15-20 feet at f2.8-3.5, and 2.0T.C. 20-25 feet at f2.8-3.5.

My question is this a normal trait of this lens. Or should i send it in for repairs. It is very frustrating for me. Also it is the first fast glass i have ever owned. And i might add very expensive. Am i expecting too much?

This is at 10 feet. I focused on the seconds birds head. No problem. But after ten feet the lens just falls off very bad. To un-usable images.

Second I am focusing on the closest birds head. Hard to see but very sharp and you can see the very thin depth of field here also.

Thanks in advance.

Last edited by garyk; 05-22-2010 at 10:21 AM. Reason: spelling error
05-22-2010, 10:28 AM   #2
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Can you tell us more about the conditions of the picture? ISO, shutter speed, etc. Also, can you put an image of the closer-taken images?
05-22-2010, 04:47 PM   #3
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The issue is that you are shoring through branches. Theyy are so pit of focus that they appear somewhat invisible. This is a problem with long lenses, you don't see the little twigs but the lens does. Try some open field shots first to learn the lens
05-22-2010, 05:51 PM   #4
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1. keep at it: getting good photos with long lenses takes practice.

2. Lowell's right about invisible branches that soften photos.

3. Try to keep your shutter speed high. The rule of thumb is 1/effective FL (eg 1/450s for a 300mm on APS-c) Go faster if you can, slower if you must.

4. A solid tripod helps.


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