Green shade in Velvia in low light

[anis]

Helo,

I am a newbie (Got my first SLR in march) and I used velvia for some

architecture shots. Most of the pictures were beautifyl, I but I

found that some of my long exposure shots (15 sec shots) had grren

shaded (Ligt sources turned green).

I have heard that this is something to do with reciprocacity

failure. I have no clue what that means? Is this normal?

Should I do something in order to prevent it?

Here is one of the picture

http://www.madhan.net/gallery/AnisVelvia/Night%20Pillars.html

 

The gallery is http://www.madhan.net/gallery/AnisVelvia/

:)

 

As always, I highly regard this forum's advice.

Thanks in advance

Anis

[jonathan_ratzlaff]

It's the lighting. The buildings with the greenish cast are being lit by mercury vapor lighting which looks almost normal to your eye but the film sees it as green. You need to add magenta filtration to improve it. The other images on your page do not show the green colour.

[david_henderson]

Don't have a lot of time but I've looked at one of your images and:

 

Reciprocity failure occurs with long (or extremely short)

exposures when the film doesn't respond to a reduced amount

of light in a linear fashion. Simply put , you need to add extra

exposure when things get very gloomy with velvia and correct the

colours by use of magenta filters. If you don't do this you get

dark slides with a greenish colour cast. You can get advice from

Fuji about what to do to avoid the consequences of reciprocity

failure on the film packs I think, or certainly on the Fuji Film web

site as a PDF. For 16 sec we're talking about +2/3 stop

exposure and a weak magenta filter. Incidentally Provia 100F

suffers scarcely at all.

 

That said, I don't think the example I looked at was the result of

reciprocity failure, or at least only reciprocity failure. There are

certain types of street light that will produce an exaggerated

green -or orange- effect irrespective of the length of exposure.

Looking at just this one slide gives me the impression that street

lighting type is a bigger contributor than reciprocity failure.

Equally you say that some of your long exposures are affected.

Reciprocity failure isn't usually selective; but the type of lighting

may well vary from one shot to another. You can buy filters to

compensate for different types of street lighting, but sorry I don't

have time to look that up right now.

[anis]

Thanks guys. Just noticed my horrible spelling. (Believe me... I am not *that* bad! ). I got more clear information about in just two posts that all of my google searches. The problem is that, I have been reading quite a lot of books and I just get the know the phrases without knowing their actual meaning.. This definitely clears up a lot. Incidentally, These are the first batch of scans from my new Canon FS4000 Scanner!

Thanks again

Anis