Filtering for a deep red filter

[Drew Bedo]

I meter with a Minolta Autometer IV F, in incident mode or with a 5-deg spot attachment. I have had poor results in the past using a deep red filter and applying a filter factor . . .either I have a mental condition or too many fingers for counting with (while juggling the meter and fighting a dark cloth while choking on the loup's neck cord.)

Can I just meter the scene through the filter to arrive at a workable exposure?

[LabRat]

Reading dark filters through different meter cells is asking for trouble... Different cells have a different response than film or transmission at their extremes, and from experience readings and exposure can been off using a TTL SLR of good camera makes... The type of cell also makes a difference...

The easiest thing to do is to convert your ISO speed with your factor (in stops or etc) to new EI and just set to the new EI (like using your R25 filter with factor of 3 stops/your ISO 100 film becomes EI 25, and you enter that directly on your meter...

Just don't forget to change your meter setting later when you change or remove filter...

All of my filter cases are marked with the stop difference on label to ease some thinking too much while using...

Steve K

[Willie]

Easiest way I know of is to do some basic tests. Start with the published/suggested filter factor and then open up about a half stop at a time for a few exposures. Develop and check the negatives and you'll get there.

[Mark Sampson]

I used to have a Zone VI modified meter, and metering through the filter worked well, at least through the mild correction filters I used. I rarely used the really strong ones, like a #25 or #29 red, and when I did, I bracketed my exposures.
(Full disclosure- I lost that meter on a field trip some years back.)

[Kiwi7475]

I’ve always used the manufacturer’s factor … it’s always worked well…. This is b&w after all , you don’t need to nail it to better than 0.5 stop, even 1 stop in many cases. The manufacturer won’t be off by that much.

A red filter will be in the neighborhood of 3 stops. Just double the meter’s exposure 3 times and you’re fine….

[Robert Opheim]

I typically use 3 f-stops for my deep read filter (B+W brand) - I have not had any problems. Check with the specific manufacturer info for your filter to see what filter factor / f-stop correction needs to be applied.

[mpirie]

The easiest thing to do is to convert your ISO speed with your factor (in stops or etc) to new EI and just set to the new EI (like using your R25 filter with factor of 3 stops/your ISO 100 film becomes EI 25, and you enter that directly on your meter...

Wouldn't that be an EI of 12, not 25 for three stops from 100?

My B&W 25 measures 2⅔ stops.

Mike

[LabRat]

Wouldn't that be an EI of 12, not 25 for three stops from 100?

My B&W 25 measures 2⅔ stops.

Mike

Correct!!! My bad... Didn't count one of my fingers...

Steve K

[Kevin Crisp]

I have a Zone Vi modified meter, and my experiences reading through a deep red filter always resulted in significant underexposure. Adding 3 to 4 stops of exposure instead hasn't been a problem. Try 3 stops as a test, adjust if necessary, and you'll be good.

[Renato Tonelli]

I follow LabRat’s ‘method’:

Set the meter for the new EI and meter; it works, you don’t need to calculate anything. I put a stycky tape on the meter as a reminder that itis set for the particular filter I am using.
I have a modified Zone VI meter but this is simpler and quicker.

[Leszek Vogt]

If you don't want to test via use of film (+processing time), you could employ digital camera. But, it's good to know how film will behave. Case in point, I was at Bristlecone Forest and the bright area of the tree would change the dynamics; therefore, one has to adjust to certain subject/s or even bracket it. Yes, I was using the red filter (B+W).

[Drew Wiley]

Everything depends on the specifics. For example, what do you mean by deep red? 24A isn't as deep as a 25; 29 is deeper still, and some brands deeper than others. That variation could account for up to a stop and a half in filter factor variance.

Some pan films are extended red sensitivity, some average, and then there is orthopan like Acros, only partially sensitive to red and essentially blind to anything beyond what a 25 will pass. And metering through anything deeply colored is just looking for trouble. There just isn't any substitute for testing in advance with each specific film and filter combination, and ideally under the same kind of lighting conditions you intend to use it.

I got lectured all the time, even on this forum, why a deep red filter can't be used in the mountains at high altitude or all the shadows will go totally blanked-out black. Well, I've been successfully breaking that rule for the past 40 years, simply because I test for real-world filter factors and then place my shadow values appropriately during exposure. Works far better than conjuring Fred Picker from the dead and asking him about some film he never heard of, or trying to turn a digital camera into a light meter. I never bracket, except for testing new combinations. A little homework in advance saves a vast amount of headaches later.

[LabRat]

To conjure Drew, I'll add that factors can change due to prevailing conditions and subjects... Like using that deep red on a "blue light" day, in open shade etc... That red filter will cut anything blue more, or green trees will darken considerably... Experience will be your guide...

Even in sunny, bright SoCal, #25 and #29 filters take some care in use... And #47B also... The safest filters I find for general use are dark greens.... They put some tone in blank skies, lighten trees, and shadow areas are helped... Plus old lenses were generally well corrected to green in the ortho days, and film generally has great green sensitivity, so a good combo... :)

Steve K

[Drew Wiley]

Takes some experience. Wind was relatively calm yesterday and I shot 3 4X5 sheets of TMY400 at a glassy estuary. Two directions with a 25red, another direction deep green filtration. Might sound like hard differences, but it will all come out quite subtly different in the actual prints. True color separation filters like deep blue 47 or 47B almost blacken both red and green. But few things in nature as quite what they seem to the human eye. Green foliage reflects a whole lot more than green, as both bees and IR film understand quite well. Fun stuff, that's for sure. But I think in terms of nuanced control, and hate any kind of overdone look.

[Ben Calwell]

[QUOTE=Drew Wiley;1645129]Everything depends on the specifics. For example, what do you mean by deep red? 24A isn't as deep as a 25; 29 is deeper still, and some brands deeper than others. That variation could account for up to a stop and a half in filter factor variance.

Some pan films are extended red sensitivity, some average, and then there is orthopan like Acros, only partially sensitive to red and essentially blind to anything beyond what a 25 will pass. And metering through anything deeply colored is just looking for trouble. There just isn't any substitute for testing in advance with each specific film and filter combination, and ideally under the same kind of lighting conditions you intend to use it.

I got lectured all the time, even on this forum, why a deep red filter can't be used in the mountains at high altitude or all the shadows will go totally blanked-out black. Well, I've been successfully breaking that rule for the past 40 years, simply because I test for real-world filter factors and then place my shadow values appropriately during exposure. Works far better than conjuring Fred Picker from the dead and asking him about some film he never heard of, or trying to turn a digital camera into a light meter. I never bracket, except for testing new combinations. A little homework in advance saves a vast amount of headaches later.[/Q




Drew, I’ve often tried coming conjuring Fred Picker from the dead, but he never answers me.

[Drew Wiley]

Oh, just fill an old top hat with some water and Zone VI modified Dektol, point your modified Zone VI meter that direction, look through the finder, and chant, It ain't workin', it ain't workin, the filter factor is wrong...want my money back... and see if the Dektol is boiling yet or not.

[Ben Calwell]

If Fred Picker’s ghost ever showed up in my darkroom, he would tell me to find a new hobby.

[mpirie]

If Fred Picker’s ghost ever showed up in my darkroom, he would tell me to find a new hobby.

If he turned up in mine, he'd probably pass away again from laughter!

Mike

[Drew Wiley]

I'd hear the bottles rattlin' on his patent medicine wagon from a mile away, and just call the sheriff and a lynch mob before he fully came back from the dead.

[Alan Klein]

Changing the ASA setting on the meter is chancy when you forget to change it back after the shot and you change or remove the red filter.

[Bob Salomon]

Changing the ASA setting on the meter is chancy when you forget to change it back after the shot and you change or remove the red filter.

Just to be slightly picky, it hasn’t been ASA for decades. It’s ISO.

[Tin Can]

Yes it is, but I prefer as I first learned ASA as they are the same

While looking this up to be correct, I found a problem with Dentists

Dental Radiography: Doses and Film Speed (https://www.fda.gov/radiation-emitting-products/nationwide-evaluation-x-ray-trendsnext/dental-radiography-doses-and-film-speed)



Just to be slightly picky, it hasn’t been ASA for decades. It’s ISO.

[nitroplait]

From the Pentax Spotmeter manual:

"When taking black-and-white pictures of a colored subject, you know that the areas adjacent to each other having little difference in light reflection, although different in visible colors, will not be reproduced on the film in proper contrast. In such a case, a proper filter is selected and used to properly reproduce the contrast.

It is difficult, however, to select a proper filter to be used for that purpose. The Asahi Pentax Spotmeter helps select proper filters. Put the filter over the objective lens of the Spotmeter and read the difference in the L.L. readings.. . use different filters until the difference in the L.L. readings (contrast) of the picture areas in question will become greatest. Select that filter which gives the greatest difference in the L.L. readings to properly reproduce the contrast.

The Spotmeter will also help correct illumination not only in color but also in black-arid-white photography. The reproducible contrast of a picture area is limited within a certain range as stated earlier. The Spotmeter readings of the various important picture areas will indicate which areas should be additionally illuminated."

In other words, just put the filter in front of your meter.

If you happen to disagree from experience; then compensate accordingly.

[Drew Wiley]

nitoplait - that odd advice has little or nothing to do with conventional filter factors, but about manipulating overall contrast through specific filter selection. Perhaps there was some application in black and white movie or TV studio sets where that method was hypothetically used, but I've never heard of anyone doing it in still photography where simple development changes work best.

[Bernard_L]

Also depends on film type. Some have a response falling to zero ~650nm, some ~700nm. Just like for the light meter's response, a small difference when unfiltered, a large difference when restricted to "red".
227529
227530

[Alan Klein]

Just to be slightly picky, it hasn’t been ASA for decades. It’s ISO.
My meter is so old the settings are still tagged ASA :cool:

[nitroplait]

My meter is so old the settings are still tagged ASA :cool:

Mine are DIN.

[BrianShaw]

One of my favorites is in Weston. lol

And one of my favorite lens/shutter is in US stop.

[Drew Wiley]

A couple of time mine were in twenty-something degrees Fahrenheit, when I accidentally dropped the meter is snowmelt streams.