IS, shutter speed and sharpness

birdfromboat wrote in post #8594572
we were already willing to pony up big bucks for larger apertures, so they equated the IS to stops of light, a commodity they could count on us buying.
Somehow, adding 25% to the price of a lens to add 25% to its ability to capture images in the hands of shakes the clown just doesn't sound as justifiable.
Of all the ingredients of good photography, stability of the camera can be left pretty much up to the operator. Lots of money can be spent on this art. Spend it on stability if you want, but I think that part of it is kind of up to me.

Well, the one time so far I've had to use IS because I didn't have my tripod available and the light was low, it literally paid for itself.

But in a way, it is about light.

If I decide that I want the shot to be taken with f/4 the light meter suggests what time I need. If that time is too long for me to hold still, I may have to bumb the ISO one or more stops. If the IS can make me take the shot without bumbing the ISO two stops, then it has gained me two stops. Obviously under the condition that the subject will be still for the additional time.

There's some good information here. I had not thought of testing my various lenses in a controlled setting to see what the absolute maximum sharpness is and then comparing to hand held shots. It sounds like a neat experiment that I hope to get to soon.

I'm not so interested in debating the actual merits of IS. IS is a technology that without doubt has those in favor and those against. Those that need it certainly appreciate it being there for sure. I also understand that the 1/focal length is a very generalized rule, thus the term rule of thumb. There are certainly photographers so steady holding a camera that the idea of limiting themselves to such guidelines is preposterous. On the other hand there are probably those with hand shake so bad they very rarely get a clear shot regardless of the settings. In between I have to believe the 1/focal length recommendation is at least a very good place to start.

The question is more this: let's say I am taking a shot at 50mm and I want an aperture of f/8. My meter tells me I need a shutter time of 1/30s to get correct exposure. Will I get a sharper shot bumping my ISO up to give me an exposure time less than 1/50s (or if you prefer to an exposure time less than my known hand shake factor) or am I better off relying on the "extra stops" from the IS system? Does it even matter? From what I have seen I am better off bumping up the ISO, but this is just from looking at past photos and certainly not a controlled experiment. I realize that subject matter makes a huge difference, so let's just assume we are talking a stationary object with a hand held camera.

In practice, it's pretty much a combination of doing what works for you. If you are happy with your IS performance, use it, but if your shutter speed is going to mess up your shot, then bump the ISO to get the faster shutter speed. Just know that the tradeoff there is getting a darker base exposure (less light) which leads to more noise in the image, so it's important that you really nail the combination so that you don't have to amp up the exposure in post processing -- if possible, get the exposure a bit to the right so that you can lower the level in post processing, but that is most effectively done if you are shooting Raw.

The IS doesn't stop subject movement at lower shutter speeds. It increases the chances of a good shot at lower shutter. You'll need lower aperture to be able to capture at increased shutter to freeze motion.

With today's cameras, you lose far less quality going up in ISO than you do risking motion blur. In a borderline shutter speed situation, I would have no problem going up to ISO 400 for nearly any purpose. Then I'd depend on IS, and I'd still prop myself or lean on something to take the picture.

As I said before, the thumbrule presumes an enlargement no greater than 8x10. If you're enlarging more than that, you automatically must start at higher shutter speeds.

A "higher" aperture, actually.

Remember that the f/stop number is the denominator of a fraction, so a larger denominator is actually a smaller quantity. So f/4 is "higher, faster, larger" than f/8, which is "lower, slower, smaller."

Thank you for pointing that out.
Yes, what I meant was a lower f-stop which means a larger aperture.