Using filters

[jimbobuk]

I just received a set of Hitech filters, a holder, various adapter rings to suit different lenses, and a Heliopan Käsemann Circular Polariser which will also fit it..

I've got the "Using the View Camera" book which talks about metering through the filters and then using the Hutchings Filter Factor, but it says this is only for when shooting black and white film.

I think buying a book on how and when to use filters wouldn't be a bad idea but i thought i'd check with you guys as well..

To be able to meter through my filters is going to be quite arkward, especially if i use graded ones as it'll be hard to hold the gradient in the right place relative to the scene to filter through the different points... The circular polariser does have a scale on it to judge the amount of rotation you have applied so it will at least be possible to do this by eye set it to what i would like, meter through it and then connect everything onto the camera, if the polariser moves during attachment i'll be able to hopefully check on the scale and reset it to where it was.. having said that i can see the scale, its not totally clear where the mark is to read against this scale!!

Having done all this though i'd have to check things are all still ok, focus wise having attached the filters.. i'm just a bit worried at light changing during all this time.

Is it possible to meter seperately of the filters and then just apply filter compensations for each filter in use... i dont have any information with the filters, though i think possibly the polariser has it written on it.. certainly the gels themselves just have their identification written on this.. i'm assuming these other filter factors are written down somewhere though for referencing.

Just wondered if someone could clear up the best way to go about using the filters, I've just found this page

http://www.largeformatphotography.info/filters.html

which is helpful but i dont think fully helps answer all my questions.. glad to hear the names of hitech and heliopan mentioned on there, seems that they are quite good after all.

[SteveL]

Spend an hour metering through your filters and note down the correction (filter factor) to be made for each one. Then apply the required correction(s) for each filter fitted when you meter for the scene.

FWIW my filters have the following factors;

81A & B = - 3/10 ths of a stop
81C & D = - 1/2 stop
Polariser (Heliopan) = - 2.0 stops
The strength of graduated filters is generally marked on the filter. I do check them though.

For example, if I have a Polariser and 81C fitted, I add 2.5 stops to my exposure. These corrections are independent of the lighting in the scene. HTH

[Gordon Moat]

Hello jimbobuck,

I once noticed a good book on filters at the local Border's Books, written by Lee Frost. Unfortunately, I cannot recall the name at the moment. Sometimes all you need is the number and letter designation on the rim of the filter, which can give you an indication of how much exposure compensation would be needed. You can often find that on the manufacturers website, or at a vendor like B&H Photo or Adorama.

Gradient filters are a little tougher. The general idea is you want to clear area to not affect the exposure, but the darker area to cut down exposure. Often used to reduce exposure in the sky and leave it unaltered for the ground. As far as what method you might like better, I think you need to try some different approaches. On the rare times I use a gradient filter, I expose the film as if there was no filter on the lens; the idea I have is to only darken the sky enough to get some cloud details, or to keep from overexposing the sky (I mostly use transparency film).

A polarizer is a little tougher. I have tried metering through the polarizer, and it helps if there are marks on the rim to keep the setting the same. I also once read someone suggesting 1 1/3 stops compensation, though I have not tried that yet. I think it can sometimes be tougher to see this effect on a ground glass than when simply looking through the filter, so I tend to adjust the polarizer prior to putting it on the lens.

Ciao!

Gordon Moat
A G Studio

[jimbobuk]

Thanks guys.. real big help... just one query.. semi related... the shutter dial on my only lens so far just seems to have full stop marks on it.. its not clear if trying to put the dial between written shutter speeds if it would actually perform the shutter at this half stop speed..

Do any large format lenses support finer shutter speed control, or are most restricted to full stops only.. its related as the filter factors you discuss seem to sometimes be in something < 1 stop that would never be selectable on my lens..

I did try timing between 1 and 1/2 a second but even that one was too quick to really tell if it was accurate, and changing at the mid (half stop) settings.

[Gordon Moat]

Thanks guys.. real big help... just one query.. semi related... the shutter dial on my only lens so far just seems to have full stop marks on it.. its not clear if trying to put the dial between written shutter speeds if it would actually perform the shutter at this half stop speed..

Do any large format lenses support finer shutter speed control, or are most restricted to full stops only.. its related as the filter factors you discuss seem to sometimes be in something < 1 stop that would never be selectable on my lens..

I did try timing between 1 and 1/2 a second but even that one was too quick to really tell if it was accurate, and changing at the mid (half stop) settings.

Hello jimbobuck,

It is actually easier to do this with aperture control than shutter speed control. As far as I know, all the newer Copal shutters common on many lenses only work in full shutter speed increments on their marked dials. Probably a good thing too, since being a mechanical shutter they can be a little off anyway, though the best assumption is that the speed you selected is accurate.

To do a filter exposure compensation with aperture setting, you can set the aperture between the numbers. Some lenses have an aperture scale with two marks between the numbered marks, others have only one slash between the numbered marks, while a few have only the numbered marks. While it can seem very error prone to move the aperture between numbers without any slash marks as reference, it is something you can eyeball and guess at with reasonable accuracy. If you have a lens that included the two slash marks between numbered marks, then those equal 1/3 stop difference.

In practice, suppose you metered and it indicates 1/15 second at f16.0. Then suppose for some reason you want to use an 82A light blue filter. The 82A needs an additional 1/3 stop of exposure. So when you look at a marked lens aperture scale, you move the aperture lever between the f11.0 and f16.0 marks onto the slash mark closest to the f16.0 numbered mark. An 82B medium light blue filter requires 2/3 stop extra exposure, so that would require a different aperture setting than the lighter 82A. Hopefully that explanation makes sense.

One of my lenses only have numbers, without any slash marks. While the aperture lever has a nice arrow shape to it, I need to guess a bit that I am on the proper mark. It is fairly easy for me to guess at a 1/2 stop setting between two numbers, but tougher to get those 1/3 stop settings. Since I shoot transparency films, it might seem like a disaster to figure this out. In reality, if it looks close to what I want, the results turn out fine. Usually there is enough room for error in modern films that you can be just slightly off and still get really nice results.

Ciao!

Gordon Moat
A G Studio

[Brian Ellis]

"Do any large format lenses support finer shutter speed control, or are most restricted to full stops only.. its related as the filter factors you discuss seem to sometimes be in something < 1 stop that would never be selectable on my lens.. "

I think it's more or less a waste of time to worry about filter factors in less than full stops. Filter factors are not very precise because the actual effect of a filter on exposure is heavily dependent on the colors in a scene. For example, the light actually transmitted through a red filter will be very different when photographing say the side of a red barn than when photographing green foliage. Fortunately black and white film is sufficiently forgiving that an exposure error of a stop or even more isn't usually fatal so we just apply the factors as best we can, rounding off fractions to whole stops, and things usually work out fine.

FWIW, I'm a believer in the John Sexton theory that with b&w film it's best to keep use of filters to a minimum. On the rare occasions when I use them it's almost always just to create separation in cases where two distinct important colors have the same EV and so would merge unless a filter was used (e.g. red apple against green foliage). But most of the time the colors in a scene are sufficiently varied that the exact effect produced by a given filter will be sufficiently unpredictable that they can do as much harm as good. Just my opinion of course.

[SteveL]

I think it's more or less a waste of time to worry about filter factors in less than full stops.

That's ok for B&W, but when using colour transparency I work to +/- 1/2 stop. There's too much variation in the other factors (light, metering, shutter, aperture, processing, my eyes! etc) to be more accurate than this.

[jimbobuk]

Thanks a lot guys.. i've dabbled with doing an aperture compensation as i noticed it was continuously adjusting.. good to know.. this information i think should be on the page that describes large format lenses as i think its VERY important, and not completely obvious that it WONT work between the shutter speeds.

I'm at a loss with the filters.. the one i plan to use the most will be the polariser, and the ND grads.. perhaps some straight NDs... I'll perhaps experiment with the filters on my digital SLR first to get a taste for free. (an experience i assume where i can just rely on the TTL metering to be right through the filters, with no filter factors to worry about?)

Thanks a lot though guys, your help as ever has been appreciated.

[Ken Schroeder]

In my opinion, Brian's posting is the most logical thing I have ever read about filtration. It has the ring of common sense in an overmanipulated world.

[Gordon Moat]

In my opinion, Brian's posting is the most logical thing I have ever read about filtration. It has the ring of common sense in an overmanipulated world.

Hello Ken Schroeder,

I agree with that, and Brian's post, if and only if one is not using colour transparency films. It seems that many of the LF photographers on this forum are heavily B/W imaging biased. The procedures for B/W imaging and use of filters do not always apply to colour transparency film usage.

When I do night imaging, I could be using Tungsten balanced film, though my choices are usually Kodak E100VS or Fuji Astia 100F. My preference is to use an 82A, 82B, or 80A blue filter for night shots. I suppose that would seem to be overmanipulated. In daytime shots, I rarely use a warming filter, and usually just shoot the film straight. While it is possible to be a little off in exposure, it is better to be fairly accurate when using transparency film; certainly not as much room for errors as one can get away with with colour negative films or B/W films.

Ciao!

Gordon Moat
A G Studio