# Filters



## PlasticSpanner (Oct 27, 2005)

OK I've finally got myself some colour negatives!  (Original problem was oxidised developer?) but I don't yet have a colour control box for my Paterson enlarger.

It does however have a filter drawer.  So what filters do I need to print in colour with a single light bulb (what are they called too!), what can I also use them for & what is possibly the better set?  I went into Jessops today for new chems but they didn't know what filters I was on about except contrast filters for B&W and lens filters for cameras. 

Also does anyone know a good place to shop for these things in the Stockport/Cheshire area?

Any help appreciated as I'm off shopping again tomorrow!


----------



## Hertz van Rental (Oct 28, 2005)

Are you going to be printing by the Additive or the Subtractive method? 
The usual set of filters consist of magenta, cyan and yellow in 0.5 increments.
These are the subtractive filters, if memory serves, and the easiest ones to use.
You put in filters of the opposite of what you want to remove. For example: to remove a blue cast you put in magenta and cyan filters (I think. It's more than 20 years since I've done my own colour printing).
It takes quite a while - every time you change your filtration you have to do another test strip for exposure. You're doing well if you can produce 6 good prints in a day.
If you are serious you would do better to get a colour head and an analyser. You should be able to pick them up second hand and they will pay for themselves in saved time and paper.


----------



## PlasticSpanner (Oct 28, 2005)

Thanks Hertz (again!:thumbup: )


I have a colour head for the Paterson but no colour control box!  I should be able to sort that out though!

Just a quick question, how do the analysers work?  I was considering getting one of the filter viewers you look through at the test print until you see what you want & it tells you what filter to use.  Does using an analyser mean I won't have to do a test print?


----------



## Hertz van Rental (Oct 28, 2005)

You have to calibrate the analyser first but once it is set up it's usually close enough to do away with a test print. Most analysers work out the exposure too.
Analysers are used in the printing machines at photo centres (like the ones at Boots and Tescos) so that should give you some idea of accuracy.
You need to remember to recalibrate every time you get a new box of paper. Batches vary.
Kodak should do a test neg - but if not it's easy enough to produce one yourself.
It's a bit like the old tv test pattern. You need a grey scale, a magenta scale, a cyan scale and a yellow scale as well as an 'average' picture. Makes for easier calibration.


----------



## DocFrankenstein (Oct 28, 2005)

I don't wanna start a new thread on this.

But what would happen if I "just expose" the negative paper in a BW head? I'm going to get a really weird colorcast, wouldn't I?

I want to experiment with color film printing sometime...


----------



## PlasticSpanner (Oct 28, 2005)

Yes.  I've just done exactly that to see the result and there is a strong magenta colour cast over the whole print which I suppose the filters will correct.


----------



## Hertz van Rental (Oct 28, 2005)

The magenta cast is due to the yellow/orange base colour of the film. The paper reverses the colours so you get their opposites.


----------



## DocFrankenstein (Oct 28, 2005)

So, I need a magenta filter to compensate for that?


----------



## Hertz van Rental (Oct 29, 2005)

Correct.
The top layer on the paper is sensitive to green light - which when processed produces magenta die. The cast means it's getting too much light so you use a magenta filter.
The rule of thumb is to add filters the colour of the cast you want to remove.
Remember that if you put in 100M + 100C + 100Y you actually produce a neutral density filter that just reduces the light. Remember to always remove the filters that cancel out to keep exposures to a minimum.

110M + 100C + 50Y = 60M + 50C 
...and so on.


----------

