Use of Tripods

Hi guys,

just a quick question at what shutter speed do you start to use your tripods for porraits?

The general rule is that you can't hand hold at slower shutter speeds than the reciprocal of your focal length. That is, if you have a 300mm lens, you shouldn't handhold unless youa re shooting at 1/300 second or faster. A 50mm lens needs a shutter speed of 1/50 or faster. Any slower than this and you need to use a tripod, or image stabilisation.

Don't foget to take into account the crop factor, as this multiplied the apparent focal length of the lens. So on a Canon 350D Rebel XT, it has a 1.6 crop factor. This means that a 50mm lens will give results like an 80mm lens. So on this camera you should use a 50mm lens with a shutter speed of at least 1/80 second.

The general rule is that you can shoot 1/(focal length x crop factor) hand held. That makes 1/80 about the slowest I can shoot with 50mm on my XTI. Some people can do much better, others much worse.
When people talk about the number of effective stops on an IS lens this is what they are talking about also. The 17-55 set to 50mm I should be able to get down to about 1/20 seconds or so.
If you are just doing portraits you might want to use a tripod anyway though just out of convenience.

can you explain what the crop factor is?

adamfromperth wrote in post #5557097
can you explain what the crop factor is?

Yes, but its easier to find someone who has already done so.
Words and pictures at http://en.wikipedia.or​g/wiki/Crop_factor

Adam, the #1 definition (the others are often misleading) is that 1/1.6x the length (and width) of the 35mm size frame is 'cut off' with the APS-C sensor. It captures a frame image that is the same as if you shot on 35mm film and trimmed off that much of the negative!...a 'crop'. The #2 definition is that on APS-C camera, the APS-C framed area is equivalent to the framed area if you shot with 35mm film camera and mounted a lens on it which is 1.6x the FL...for example 50mm lens on APS-C is similar in the framed area to using 80mm on 135format body.
Since the image on the sensor is smaller, it has be magnified 1.6x more to make the identical final size print. And it is the 1.6x increased magnfication which is responsible for the handheld speed to be stated as 1/(1.6 * FL).

Any time I want repeatable images, regardless of shutter speed. Lets me talk etc without recomposing each shot. Keep the remote release hidden, and blast away.

Shutterspeed is not just what decides wether or not to use a tripod.
I sometimes shoot handheld at just manageable shutterspeed, I sometimes shoot of tripod using studio flashes...