*%@!ing Red filters!

[Joe VanCleave]

I noticed this same problem when I tried a deep red on my Lumix G1. Then I tried the polarizer, and found that it works very well, here's an example:

 

[RalphLambrecht]

Ralph, my comments below are just my opinion so I'm not saying that it's wrong as I realize I may be missing something from your post, but this is my thinking as it relates to your graph. I have my own simple graphs to illustrate my point, right or wrong.

I believe the discussion of a film's exposure latitude ends when we have to resort to development modification to keep the highend luminance values of the subject to within printable densities on the negative. IMO, at that point, we have exceeded the latitude of the film, that is why we have to modify it's development to maintain printable densities. Your graph indicates that latitude extends to beyond Zone XII (Log E 3.6). IMO, a film's exposure latitude is strictly within the context of how much exposure variation can be given the film (in low contrast subjects) and still keep the high end values easily manageable given normal development.

High contrast scenes do not allow much, if any, exposure latitude. I can make use of my film's latitude with important densities that lie between Zone I and Zone V, because I know that I may also provide exposure from between II to VI; III to VII; IV to VIII, an V to IX for that same subject, provide normal development, and have printable densities through IX (IX being just like I in that it has tonality but no real texture). I may provide plus development in a low contrast scene which is a development modification, but that modification itself has its results still within easily printable high end densities.

As soon as I have to resort to modification in development just to be able to print Zone X densities or higher, latitude is a mute point it seems to me. There has to be a limit to latitude and to me, your graph does not indicate one. You obviously know what you're doing and you have some awesome photographs, perhaps my thinking on film's exposure latitude needs a make over.



Very much agree.

Chuck

Chuck

Nothing wrong with what you're saying, but overexposure latitude was not the point of discussion. Let me rephrase my statement to include it:

There is NO underexposure latitude. Overexposure latitude depends on the subject brightness range but can be modified through development.

 

[RalphLambrecht]

I noticed this same problem when I tried a deep red on my Lumix G1. Then I tried the polarizer, and found that it works very well, here's an example:

Polarizers don't have a uniform filtration. The filtration depends on the angle towards the sun as one can see in your picture. The sky is much brighter on the left than on the right. Red filters don't have this issue.

 

[RalphLambrecht]

Back in the dark ages when as a young photographer, I couldn't accept any result that wasn't over dramatized, I started using a red filter and was very disappointed that even with the three stop factor, I still lost detail drastically in the shadows.

I think your question is a very important one. I think that we can safely presume that the manufacturer uses a neutral gray, not just a mid value, but also one with no deviation in hue from neutral. Beyond that, I wouldn't guess.

It's more complicated than that, I think, which makes it harder to apply in individual circumstances. My loss of shadow detail puzzled me, but to compensate I began to give four stops filter factor, and alter the development accordingly. Worked much better.

Here's what I came up with:

Shadows are shadows because direct sunlight is blocked by a solid object. The filter darkens anything blue/cyan/green. The sky is blue (didn't you know?) or may tend somewhat toward cyan. Anything illuminated exclusively by skylight, then, is lit with blue/blue-cyan light. So, as the filter darkens the sky, it also darkens the shadows, which are lit with only the light coming from the sky. As landscape painters discovered long ago, shadows don't look right if they aren't a bit on the blue side.

Good point. Shadows are inherently rich in blue light, and so is some foliage. Hence the loss of shadow detail with red filters.

 

[Joe VanCleave]

You're correct, Ralph, about the directionality of polarizers. However, when I tried the red, the polarizer and also both filters simultaneously on my G1, I could only get a significant darkening of the sky with the polarizer; that is, applying the red filter with the polarizer did not visibly darken the sky any noticably additional amount from the polarizer alone. FYI, this was using a circular polarizer.

I also captured some red-filtered color images and toyed with them in PS at home into B/W conversions; I could not get the sky darkening effect nearly as evident as these in-camera JPEGs using the circular polarizer. This somewhat surprised me, given my past experience with film cameras and red filters. It may have something to do with the G1's sensor bandwidth not extending as far into the IR as does B/W film.

~Joe

 

[Q.G.]

Film doesn't extend into the IR band at all. Sensors do.
But that's moot, since blue isn't red, let alone infrared. A red filter should have an effect, no matter if sensor or film.

A red filter has a greater effect than a polarizer. A polarizer will be able to darken the sky too, but only a small part of it. The red filter will darken every bit of it, as long as it is blue.

That adding a filter to another filter that already blocked the light the second filter would block has no effect is to be expected. You should have compared a red filter alone to a polarizer alone.

(By the way, circular or linear doesn't make a difference.)

 

[photomem]

Film doesn't extend into the IR band at all.

My SFX, Tech Pan, and Rollei IR film would beg to differ.

 

[RalphLambrecht]

My SFX, Tech Pan, and Rollei IR film would beg to differ.

Kodak TechPan has no spectral sensitivity beyond 700 nm. Hence, it's not sensitive to infrared radiation.

 

[photomem]

Ok, so IR film goes up to 890 nm, and infrared looks to start around 1000 nm.. maybe we are both correct?

 

[RalphLambrecht]

Ok, so IR film goes up to 890 nm, and infrared looks to start around 1000 nm.. maybe we are both correct?

Infrared radiation is >700 nm.

 

[Q.G.]

My SFX, Tech Pan, and Rollei IR film would beg to differ.

Good.
Just about any other film would not.
The FP4 and Delta used by the OP certainly wouldn't.

Tell you what, let's now assume an orthchromatic film has been used, and continue discussing the use of red filters.

 

[Vaughn]

Good dark tones with that combo, man...

 

[Q.G.]

Would you think adding a polarizer would do much to improve on it? And if so a linear or a circular polarizer?
...

 

[Vaughn]

If the direction of this discussion is a clue, I would have to say circular...

 

[Q.G.]