Grad filters and film...

ChrisR

ChrisR

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I'm planning to replace my charity shop Cokin A filters with P size, for a bit more flexibility. AFAICS the SRB holder looks good (I'll check it out at The Photography Show). They also sell P size filters at not unreasonable prices (so also do Kood, as well as Cokin). I noticed that SRB sell grad filters in 1, 2, 3 and 4 stop densities. Currently I think the grads I have (A120 and A121?) are 1 and 2 stop, and I almost never use the 1 stop. I was thinking, with the flexibility of film, would it make more sense to buy a 2 stop and a 4 stop? The latter would reduce the need to stack filters, reducing colour casts...

Is there anything else I should be thinking of, with the expected use including 35mm cameras (49mm filter thread and up), MF (currently only a Minilta Autocord, so not really relevant, but who knows with the encouragement of the F&C collective?) and the forthcoming Chroma, perhaps with a 90 and 150mm lens?
 
When I used to be well organised :rolleyes:, I made a list of filter sizes for all the lenses I had at the time. A quick look at the LF ones shows the Caltar 150/f5.6 as 49mm, the Nikon 300/f9 as 52mm, the Schneider 210/370 convertible as 58mm and the Nikon SW90/f8 being biggest at 67mm, so you'll probably be fine with 84mm P size filters as your format size goes up.
 
I'm pretty sure stacking 2x 2 stop grads will produce the same cast as a single 4 stop. This is because the grads are dipped in the same solution for different times to achieve different densities. Therefore to achieve the same optical density there has to be approximately the same amount of material (dye), and hence because the spectral response will be the same you'll get the same cast. This is governed by the Beer-Lambert law. I'm conveniently ignoring the increased number of interfaces and the (small) losses associated with each. As such I'd recommend getting a 2 stop and a 3 stop. If you broadly generalise and say that print film has roughly ten stops of dynamic range, using a 4 stop grad would imply that a scene has ~14 stops of dynamic range... When was the last time you saw a scene with that much contrast short of metering off the sun :D ?

Personally also, get soft graduation filters rather than hard as they are way more versatile.

For LF, screw in cable releases are a must IMO, if you've not got any already that is. Prodding the lens right at the moment you're exposing an expensive piece of film is a bad idea.
 
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Peter B said:
When I used to be well organised :rolleyes:, I made a list of filter sizes for all the lenses I had at the time. A quick look at the LF ones shows the Caltar 150/f5.6 as 49mm, the Nikon 300/f9 as 52mm, the Schneider 210/370 convertible as 58mm and the Nikon SW90/f8 being biggest at 67mm, so you'll probably be fine with 84mm P size filters as your format size goes up.
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Thanks Peter. P size adapters go up to 82mm so there's still a bit of room to spare.

Woodsy said:
I'm pretty sure stacking 2x 2 stop grads will produce the same cast as a single 4 stop. This is because the grads are dipped in the same solution for different times to achieve different densities. Therefore to achieve the same optical density there has to be approximately the same amount of material (dye), and hence because the spectral response will be the same you'll get the same cast. This is governed by the Beer-Lambert law. I'm conveniently ignoring the increased number of interfaces and the (small) losses associated with each. As such I'd recommend getting a 2 stop and a 3 stop. If you broadly generalise and say that print film has roughly ten stops of dynamic range, using a 4 stop grad would imply that a scene has ~14 stops of dynamic range... When was the last time you saw a scene with that much contrast short of metering off the sun :D ?

Personally also, get soft graduation filters rather than hard as they are way more versatile.

For LF, screw in cable releases are a must IMO, if you've not got any already that is. Prodding the lens right at the moment you're exposing an expensive piece of film is a bad idea.
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I was just going by the persistent internet rumour that colour casts seem to show up particularly when filters are stacked... mind you, I think I've read as many posts saying nay, no trouble mate! (On second thoughts, this might refer particularly to NDs rather than grads... the latter are often used for eg golden hour shots where the colour contrast is already pretty extreme!)

BTW I'd have thought the 5 stops (or so) on transparency was more relevant to the calculation than print film (I presume you mean negative film... and I thought that was 7 stops?)?

However, a 2 stop and a 3 stop means I could buy both as Kood filters which I think have rounded corners, allegedly making them easier to slide in! I was thinking of soft grads, which is what I think I have in the A size.

I do have a cable release, with a locking collar, not very long but probably enough.
 
Some time ago, I came across a remark by Joe Cornish (who uses/used Velvia). He'd seen the landscape work of another photographer who used colour print film, and said photographer found no need for graduated filters. I'll admit that my position is one of profound practical ignorance with grads, having never actually used one in my life. So I'd say it's going to depend on the film.
 
joxby said:
coloured grads for b/w ?

I have one for bostin sky, but then, b/w is 99% of what I shoot


:coat:
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I was planning on getting some coloured square filters for black and white, but hadn't thought of coloured grads for that purpose. (I do have a tobacco grad in the Cokin A set, but I've never used it and I suspect it doesn't really do the same job as a yellow grad... which I've never seen!)
 
I've got a red and an orange, though I've parked the red pretty much.
It makes for interesting exposure calcs and framing, on one hand you want to account for the stop/stops, but on the other you don't wanna blow highlights in the areas not covered by the grad.
All in all, it feels like you're over complicating the situation, so you just ignore the calcometer part of your brain and toss a coin...:D
 
I've thought about what I just wrote, and the reason its like that is because I'm not using a coloured grad for the same reason I'd use an nd grad
 
@ChrisR
I have a couple of Kood Pro filters you can have if you want. Don't think I ever used them.
Non grad unfortunately but there's an ND2 and an ND4 if they any good to you.

Free of course.
 
desf said:
@ChrisR
I have a couple of Kood Pro filters you can have if you want. Don't think I ever used them.
Non grad unfortunately but there's an ND2 and an ND4 if they any good to you.

Free of course.
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If that's P size, I'd be grateful, thanks, maybe pick them up next time I'm in Edinburgh? (That's probably a small enough transaction not to worry about classifieds, isn't it? If the mods object, we should do it that way.)
 
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