This is not strictly true. Tripods are advisable, but not necessary. Use the 1/focal length rule. With film, this would simply mean making sure your shutter speed was faster than 1/320 (the closest corresponding shutter speed to a 300mm focal length).
But with DSLR it gets a bit trickier, in that the sensor is APS-C sized, not full frame 35mm. On Nikon, this gives you a 1.5x crop factor, meaning your lens when zoomed out to 300mm behaves like is 300 x 1.5 = 450mm. (Any other photographers reading this - I know that’s not strictly correct, but it’s fine for the purposes here).
So now your lens at 300mm is thinking it’s a lens at 450mm. So, using 1/focal length, a shutter speed of 1/500 or faster should result in an image that is free of shake. Providing you know how to hold a camera properly etc, that is.
If it’s daylight, but still not bright enough for 1/500, simply crank up the ISO until it is. I get usable (professionally) images out of my DSLR (Canon 20D with “L” glass) at ISO1600, so I see no reason why the Nikon D50 can’t produce good images at that setting.
If you’re using the macro feature on the lens, then you’ll have to use a tripod - in fact, for all lenses when shooting macro, a tripod is the best way to go.
Do realise that the Tamron 70-300 is a fairly cheap lens, and the quality, while not bad, is not terribly good. Stopped down (f8 or so) its good between 70 and 200, but even stopped down, between 200 and 300, images will tend to look a little soft.
Do you shoot in RAW or as JPEG? I’d recommend shooting RAW and doing the post process yourself if you’re not already. One thing about DSLRs, is that there’s an anti-aliasing filter in front of the sensor, and so RAW images (and JPGs if in-camera sharpening is turned off) will look a bit soft when you first view them on your computer. You will need to apply some sharpening in PS.
Anymore questions, feel free to ask.[/quote]
Anyhow, this is a whole other can of worms, but I disagree with your recommendation to shoot RAW. I know, the whole RAW vs. JPEG debate is one of the more obnoxious forum topics to argue about, worse than MS vs. Apple or Canon vs. Nikon. But you will not get any sharper pictures from RAW. Sure, with RAW files you have more control over color temperature, you can recover a half stop’s worth of blown highlights, you can avoid posterization that’s apparent when you’re printing at around 11 x 16 by staying strictly in 16-bit mode. But to put it bluntly, if you’re asking how to get sharp images out of a consumer-grade telephoto zoom, RAW is going to be much more of a burden than JPEG. Personally, I only shoot RAW when I’m shooting sunrises or sunsets.