Long exposures during the day

[mox]

I want to take long exposures during the day.

There is many solutions like changing the f-stop to something like f/22 but still I can only do ~1-2 secondes at ISO100

I've been told to use a Neutral Gray Filter (+8) wich is doing EXACTLY what I want

But I was thinking.. what if I use two Polarizing filter ? You know, when you put a polarizing filter in front of an other one.. if you turn one of them, you change the 'transparency'... can this gives the same effect as a Neutral Gray Filter ?

 

[ksmattfish]

A polarizer blocks about 2 stops of light, which would adjust your 2 sec @ f/22 to something like 8 sec @ f/22, or even more time with reciprocity failure (see your film manufacturer's website for long exposure adjustments). You could stack filters, or choose a lower ISO to get even more time.

 

[mox]

btw, I have a DSRL Canon 10D and the minimum iso is 100

 

[tr0gd0o0r]

You may run into some noise problems w/ a DSLR with longer shutter speeds like that.

more time with reciprocity failure

I just had a thought about this. Is recprocity failure and issue with digital cameras? I thought the reason it happened was a breakdown of the chemical reactions with film. Does that still happen w/ digital, or is it built in somehow?

 

[Digital Matt]

You may run into some noise problems w/ a DSLR with longer shutter speeds like that.

You will have no noise problems at ISO 100 on a 10D and several seconds of exposure. You can do exposures of probably 10-15 minutes with no real problems, and noise can be dealt with in a longer exposure.

 

[ksmattfish]

I just had a thought about this. Is recprocity failure and issue with digital cameras? I thought the reason it happened was a breakdown of the chemical reactions with film. Does that still happen w/ digital, or is it built in somehow?

Good question. I think it would be different.

 

[j_mcquillen]

I don't think using two polarising filters will be the best option for you here...

Yes, it will cut out a lot of light to the lens, but with 2 polarising filters stacked up, you'll risk vignetting as the edges of the filters intrude into your image, and increased lens flare as light bounces around between the multiple surfaces - far better to use a single flat Neutal Density grey filter - you can buy types that will probably cut out more light than 2 polarisers anyway.

Remember with photographic polariser filters, the effect you describe (of changing the 'tansparency' - darkening skies, and cutting out reflections)occurs with only one filter neccessary.

 

[Unimaxium]

Regarding film, I thought reciprocity only breaks down when you get up closer to 1 minute, but not as short as 8 seconds (and on the other end, faster than 1/10,000th). I could be wrong, as I've never really had experience with long or fast exposures, but I thought that was what I heard.

 

[Hertz van Rental]

Regarding film, I thought reciprocity only breaks down when you get up closer to 1 minute, but not as short as 8 seconds (and on the other end, faster than 1/10,000th). I could be wrong, as I've never really had experience with long or fast exposures, but I thought that was what I heard.

The exposure durations at which reciprocity effects occur vary with the type of emulsion. Reciprocity is not normally a problem with 'normal' b&w films* but is much more of a problem for colour film.
Always refer to the manufacturers data sheets.


*Kodak recommend that development and exposure compensation is made for exposures shorter than 1/2000 of a second or longer than 1/2 of a second.