I agree with the width - exactly 50mm.

I make my image height as first displayed 33.5mm.

Then if I zoom in on any part of the image, it becomes 50 x 37.5 as Robin says.

Is this actually true?

Or does the 'charge' arising in the CCD occur only when the sensor is exposed to light?

Several of the articles I've come across describing how CCDs work are pretty technical, and I don't pretend to fully understand them, but they all talk about charge arising due to the incident light, and that charge then being collected and converted into an output voltage and amplified.

I haven't seen anything saying that as well as this, the CCD is charged whenever the device is on (whatever that means).


Another thought that occurs to me is the dust removal cycle. If a static charge is helping to make the dust stick, you'd think they'd remove it before trying to shake it off, wouldn't you?

Ah, but this is the thing. It may involve a risk, but it may prevent other risks.

I probably change lenses about as often as every 20 shots too. So in a year, I've saved something close to 1000 off switch operations by not switching off for a card removal or a lens change. (I never turn SR off on the tripod either. )

Who can say whether if one of my cards dies, it's actually related to my lack of good practice, or something else. And maybe the 1000-odd switch operations would result in an earlier failure, and a more expensive repair than the replacement of the odd card.

I don't think the actual probability of any particular failure mode is high enough for a definitive answer to this one.

As risk of incurring much derision from those here that do do all this, I don't.

In 8500 shots, with an average of about 20 shots between each image harvest, I've never once switched off the camera or ejected hardware before pulling the card. I don't switch off between lens changes either.

So far (famous last words ) I've never had a card problem, either, and I don't get the impression I suffer from sensor dust any more than average.

I may well have just been lucky, but I suspect the likelihood of things happening if you don't take these precautions is a lot lower than the occasional scare might suggest. I also suspect that when problems do occur, they're attributed to not taking such precautions, without much actual evidence for this being the cause.

I do, however, treat all these things extremely gently, never forcing, never bending, never applying any more pressure than required to just get lenses, card doors, cards in readers, etc, to 'click home'.

The thing that makes this topic excellent in my view is that although the brief is broad, it's broad in a way that lets us relate very easily to it. The double meaning (light as in weight) is clear, and we've all got experience of seeing photos that capture something special about the light in the scene.

I note that whereas every single one of the 'My day' entries, AFAIR, had a title explaining how the photo related to the theme, out of 24 entries so far this week, only one title explains anything about how light relates to what's going on in the picture.

30,000 shots they claim for its life ISTR.

I unscrewed mine to see what was inside - it's just a standard cell so it would be easy to replace.

For about £20 you can get a genuine Pentax remote control F, which definitely does work for Bulb exposures. You just hold the button down for as long as you want the shutter open.

I suppose an almost new one might have loose bits too. I don't know - I'm only speculating. You were probably just unlucky.
Ah well, sure, but you didn't say that. We were all talking in the context of shifting muck from the sensor. Sure - a blast at the end of the lens is probably no bad thing just in case it's picked something up.

You'll probably never know what caused it, so no point worrying.

Or in the blower, if you use it every time you change lenses. Maybe the plastic is breaking up inside. Or maybe it's a chunk of grit from all the burning.

Doing it that often is excessive, IMHO, though. There's no point taking the risk of blowing something on to the sensor as often as every lens change.

Just do it when you notice a bit of crap on there, and clone it out of the images it affects.

Yes, absolutely. I guess I get the nozzle to within about 1cm of the sensor, so a bit further in than the mirror. That's about as close as I dare go, and I haven't needed to go any closer.

I can't imagine it could be done more cheaply than replacing it.