Red Filter and B/W Film

[markus_muller]

<p>I bought a Heliopan red filter (25) for my sinar 4x5.( http://www.foto-mueller.at/shop/pd48783797.html?defaultVariants=search0_EQ_28%20x%200,75%20mm_AND_{EOL}&categoryId=210 )<br>

Is it correct to open the aperture 3 stops more for a proper exposure?<br>

I don`t want to mess up a box of film (again)</p>

[jim_norman4]

<p>Not all Red 25 filters are the same. Generally, for that filter, somewhere between 2 and 3 stops will be "right." You can check by using your spot meter, but there are differences relating to the type of film you're using. Each film has different sensitivities to different wavelengths of light. Your best bet is to do some testing, using your film and your filter and decide what you like best. Take good notes! On top of all that, the scene itself may affect what you want to do. You didn't mention whether you're just trying to darken the sky or perhaps something else. The red filters (25 and 29) produce a very evident effect. If the sky darkening is your aim, you might think about an orange filter. </p>

[markus_muller]

<p>thanks jim,<br>

yes, darken the sky is my aim. I had a shooting with the filter yesterday. I used an efke 25 b/w film.<br>

I opened the aperture 1 stop more- unfortunately i badly underexposed about 10 sheets. All shots without the filter are proper exposed.<br>

So I will repeat the shooting tommorow. I think I`ll try 3 stops...</p>

[tim_ludwig2]

<p>Markus,</p>

<p>Just to throw another thought into the works.....if you want really dramatic skies, run some tests with both the red filter and a Polarizer (adding another 2-2.5 stops for the Polarizer over the red alone. Blue skies will go nearly black and separation from clouds is wonderful. It is a very dramatic effect and not for every scene, but when it's right, it's incredible.</p>

[ron_miller5]

<p>Meter through the filter and add 2 stops.</p>

[markus_muller]

<p>Yesterday I took some test shots. With the filter I need to add 4-5 stops (!)</p>

[oistrakh]

<p>That doesn't surprise me, it depends on what you are metering and how you want the scene to look. For example, I regularly use a #29 filter. When I meter, I spot meter what I want at zone III and close down two stops. But because i shoot a lot of landscape, what I want at zone III is frequently dark green leaves. The filter reduces those far more than a neutral gray color, so simply adding three stops for the filter is not enough. In practice, I have found that I have to open up four stops in order to compensate for the effect of the filter, if I want my zone III to come out correctly.</p>

<p>It all depends on what you like to shoot and how you are metering your scene.</p>

[vinny_walsh]

<p>He's using efke 25 film which has a sensitivity to red that many other's don't. I don't use (and wouldn't recommend) anything stronger than a orange 21 with this film. That's why you're needing to add 4-5 stops to get properly exposed negs.</p>