Reciprocity Failure ?

I know this may be a silly question but I want to try some night shots with the D in Lincoln. Does it suffer from reciprocity failure in the same way film does?

Kim

I've asked the same question of many people, and so far nobody has known the answer.

You can of course test it very quicklyin the field by looking at the replay and then adjusting exposure accordingly.

When I did night shots I didn't become conscious of any great degree of reciprocity failure, but exposures did not generally exceed 30 seconds.

Hi Kim,

A quick browse through the web seems to suggest that RF doesn't apply to digital, but long exposures do increase noise, which you obviously don't get with film. The D seems to handle this okay though, when noise reduction is switched off.

I did some 1 minute exposures a while back, as well as 4 and 16 seconds, and didn't notice any great variations in exposure.

Best thing though is just to try it out!

And don't forget to wrap up warm.

Dan

I will try it and find out. Will probably take the LX as a backup.

Kim

remember also, that in the dark, your lcd will appear much brighter than you'd expect. severe underexposure will result if you use it to gage your shots. check your histogam and highlights carefully.

Well, I can give you a very definative answer and a reason for it, but I don't know how good I am at describing it...

I assume you understand that film reciprocity failure occurs because film exposure works on a logarithmic curve (note: same as film characteristic curve). When something is recorded on film at it's minimum recording ability (the toe) exposure takes longer than typical exposures we are used to (taken at the straight line section). Never mind about the upper section (the shoulder) for this description...

In digital cameras, the sensor records information in a linear curve, i.e. no curve at all. As soon as light reaches the sensor, it records it at the same rate regardless of whether it's 1/1500000000th of a second or 1500000000000 minutes. Hence no reciprocity failure in digital cameras.

Of course as mentioned, digital noise becomes a problem. As with any electronic gadget, heat occurs when it's running for a long time.

Noise isn't just a result of photo sites being placed close to each other, or their size, but when heat occurs, more disruption is made to the signal, and that is the reason for noise occurring more at longer exposures.

Hope that helps.

That's why in high end imaging applications such as photospectrometers which use CCD's the CCD's are often cooled by a peltier element and in more exotic systems even with liquid nitrogen.
Heat can do strange things to all electronic components.

I have read somewhere that someone used a cooling element which you use in your coolbag or coolbox when you go to the beach. He attached it to the back of the camera to cool it down. This was for astronomy pictures with very long exposures. The problem with cooling this way is the risk of condensation.
Ideally you should have an active cooling system which takes into account the dewpoint and such, but that will be impossible to use on a portable system like a camera...

So on the fabled K1D we want a big heat sink?

well now that they got dust/moisture sealing on the lenses, I see no reason they can't stir up a little cyclonic windstorm inside the camera with a miniture fan...to cool the sensor and collect the dust.

So will we see a note in the manual acknowledging technologies from Dyson ? If so, I just hope Pentax never produces a yellow bodied digital SLR

Cheers,

What, like this?

Oh but Peter, think of the possibilities...








Dan

With digital you may be better off creating a "stack" by combining many reasonable exposures together. More work in PS, but the noise is easier to control that way. (Do a Google for astronomical stack and you should find a few ideas)
Matt

Haaaaaaaaaaaaaaaaaaaaaaaa!! ROFLOL

I'd have to go for the purple one to go with my Dyson. Although that's got more turquoise on it. Who thinks up these colour schemes???

Dan