Are they anything like this:




This was with a 5MP Sony DSC-T3; several others were similarly afflicted.

It wasn't gunk on the lens, or condensation (the camera had been at room temperature for hours, and other shots taken shortly before and after were not affected.

Never got to the bottom of it, haven't seen it since.

Ah yes. Here we agree again. That's twice in the same thread - whatever next

My budget, sadly, is not unlimited. So I have to make do with what I've got. A 400mm lens is the best I can do for shooting the moon - so without a telescope, adaptor, tracking motor thingy, I just have to do the best I can, which to date is this:

http://i162.photobucket.com/albums/t244/chris5gd/Public/IMGP2385-1b.jpg

I tried getting a bit closer, but it wasn't any better from the bedroom window than the front garden...

(PS that's the Sigma, not the Pentax, for those that have been following my other thread. I'll see what I can do with the Pentax when I get a chance)

Well yes, absolutely.

But let's change just the one variable at a time, shall we?

Agreed. I've never disputed this, in any of the ways you've expressed it. If I've appeared to, then I'm sorry.

This is where we differ.

Because if I do crop, from the tip of his nose to the tip of his tail, which is what I was after in the first place, I'm getting the same number of inches of squirrel in both situations; they take up the same space on the sensor and on the film, and I enlarge them to the same size. This is the same picture - the same print, anyway.

And if I use the same shutter speed, the visible shake will be the same too.

As Matt says, it's a rule of thumb. All I'm adding is that you need to know how to use it.

If my squirrel was Ok with film with that exposure at 6x4, it still will be with digital - I just chuck away more of the original frame with the film than I do with digital.

George, I understand this perfectly, but with respect, you keep saying effectively the same thing, and not addressing my point.

If some shutter speed with some lens (say 1/400s with a 400mm lens) is enough to render a picture of a distant squirrel enlarged to say, 6x4, shake free on film, surely the same exposure on digital, with the same lens, will be enough to render the same squirrel at the same size on the print also shake free, since the size of the squirrel is the same on either film or sensor, and is enlarged to the same size.

I don't see why I need 1/600s when the image of the squirrel is the same size, and it's being enlarged the same amount.

Granted, it's a different percentage of the frame, but I don't want the whole frame.

I hate it when people say "it really is very simple", since even if you're less paranoid than I am, it's not hard to hear, or at least imagine, the sigh in their voice, and the unstated "you fool" at the end.

I absolutely understand the enlargement issue.

With long focal length lenses (which is when you have to worry more about shake), however, at least in my experience, the intention is often to photograph something a long way away, not to compose for the whole frame.

So if I want to take a picture of a distant animal, for instance (or Dan's tennis ball example), I'll want to choose the longest lens I have, and then enlarge the animal part of the image to a suitable sized print.

In this case, the image of the animal in the camera will be the same size whether it's film or a digital sensor. If I then want the animal blown up to a 12x8 print, it seems to me that the amount of shake will be the same.

Ok, so far, this is exactly as I had it.

Yes, absolutely. You've made a bigger enlargement of the ball, by blowing up a smaller angle of view (with digital) to the same size print as the larger angle of view (with film). So any shake will be more visible because it's a bigger enlargement.

However, if you enlarged the ball on the film negative and the ball on the sensor image to the same size, by this argument the visibility of the shake would be the same, which is what I thought.

I think I understand. If this was George's argument as well, then it boils down to the fact that if you make two different enlargements of the same sized image, you'll see anything that's out of focus more easily on the larger enlargement.

Sure. If you're aiming for the same sized print, off the whole of the available frame from digital and film respectively, you need to get the same angle of view, so that means different lenses.

In this case, the print from the 200mm on digital has been enlarged more than the one from the 300mm on film. Comparing the shake in these two situations is much harder, since with two lenses, you have two lengths, and two masses, so it's harder to know which one is going to shake more.

I thought I'd understood all this

Is it not the case that if you take a picture with the same lens of the same thing at the same distance, the image of that thing is the same size, regardless of the sensor?

I realise you won't get as much of it on to the digital sensor as you would with the film, but I thought the image itself would be the same size, and thus similarly susceptible to shake.

What am I missing?

Supplementary question: is the sensor the same distance back as the film plane was?

Fair enough... here's one back...

Strangely, I won a Mars bar once, at school, as 1st prize for compiling one in French. I haven't done any since, though, nor does it interest me.

I wasn't expecting, or even hoping to win this one, with that little snap. It's not a good photograph, I'm not claiming that it is. But if you intended your comment to be as disparaging of the ideas as it sounds, it's a little disappointing that there's so little room in composition for the offbeat. My apologies if I've misinterpreted you.