mrbass111 wrote in post #5563119
the main reasoning is shooting birds under low light. even useing iso 1600 early in the am i am still at 60 shutter speed and my pics come out blurry. it sound like left exp. might be usefull early then adjust to normal ap. as light permits. thats just what im getting out of all this. but my other problem would be as light gets better am i better off going iso 800 then 400 to get better pq?
and if i do lower my iso. i would think that i should use negative exp. to get faster shutter speeds. am i right on this?
I'd say underexposing should be a last resort (rather than a "helpful technique"), but there will be times when you really don't have a meaningful choice -- like you've said, the shutter speed will be so slow that any animal movement will cause blur.
I'm assuming that in this scene you're using a tripod, right? So that the only blurring would be from the bird?
At any rate, when you underexpose, you are stuck with a low signal to noise ratio, meaning that you collect less light relative to the amount of inherent noise that lurks in the system, so that when you amplify the exposure in your software, you amplify the noise as well as the light and the noise becomes more of a problem. The higher ISOs will also have more noise, so you get hit by a double whammy when shooting in this kind of low light.
Shooting in RAW gives some help because you can fine-tune things in your RAW developer whereas with jpegs you have frozen and shrunk your image to fit the jpeg format, but still with RAW you'll be faced with the noise and will need to work with your RAW noise reduction tools.
A lot of times the noise is more in darker backgrounds than on the actual birds, so you can also consider bringing a shot into Photoshop and separating the bird from the background in layers and then applying different amounts of techniques to soften noise and sharpening to the different layers.
One other bit of advice: consider using a good flash, such as the 580 EX, and a flash extender such as the Better Beamer. Many people get good results using these with birds in low light. They are made to be used with telephoto lenses of 300mm or more in exactly these kinds of situations.
Lastly, if you are serious about all of this, you might consider a body with better high ISO performance such as a 40D, which will give you cleaner images at 1600 and will allow you to go to 3200. Also, I've never used the Sigma lens, but you might do some tests as to how the lens performs at the widest aperture, which I assume is f/5.6 at 500mm. Some lenses are noticeably poor performers at their longest reach and widest apertures. If you see this with your lens you'll have another factor you'll have to deal with in choosing your exposure settings. When I saw that problem with my first telephoto lens (the EF 70-300 IS) it prompted me toward the inevitable "L word"
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yes, and i do use negative exposure settings
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