Exposing using a red filter.

[LifeIn35mm]

I am going to start using filters and was wondering if you expose the image any differently then what the meter tells you with a red filter? The one I will be using is a Hoya HMC.

 

[BrianShaw]

If using an in-camera TTL meter and the filter is attached, just meter and shoot. If using a hand-held meter, meter normally (without the filter in front of the meter) and open 3 stops to account for the filter.

 

[Old-N-Feeble]

It depends on how deep the filter is... #23, 25, 29. Even then, it also depends on the film's spectral sensitivity plus the subject matter. It's been so long for me that I can't remember but I suggest you state the Wratten number if you know it plus the film being used.

 

[Jeff Kubach]

Depends how fast your film is. If it is slow you might have to use a tripod.

Jeff

 

[LifeIn35mm]

It depends on how deep the filter is... #23, 25, 29. Even then, it also depends on the film's characteristic curve plus the subject matter. It's been so long for me that I can't remember but I suggest you state the Wratten number if you know it plus the film being used.

I shoot 400. It's 25a the website says.

 

[andrew.roos]

If you look at the ring around the filter from the front, you will probably see a number followed by "x" (for "times" as in multiplication). For example, my red filter has "5x" on the front. This indicates that the exposure when using the filter needs to be five times longer than without it, assuming the aperture and film speed are the same. This is called the "filter factor". The filter factor for a red filter will probably be in the region of 4x to 8x, depending on how dark a shade of red it is.

If you are using a camera with through the lens (TTL) metering - which includes most (although not all) SLRs that have meters - then the exposure meter will see the reduced amount of light coming through the filter and will base the exposure on that. So although the exposure will still be increased by the filter factor (for example, 5 times as long with my red filter), you do not have to change any settings on the camera to achieve this. Just meter and shoot normally, taking into account that with the longer exposure you may require a tripod.

If you are using an external light meter, or a camera that uses non-TTL metering, then you need to adjust the exposure to take account of the filter factor. Many external light meters have a scale for precisely this purpose - e.g. with my Gossen Luna Pro, I simply set the filter factor scale to 5 when using my red filter and meter normally. If it did not have a filter factor scale, I would calculate the exposure without taking the filter into account, and then multiply by the filter factor (5 for my red filter).

 

[andrew.roos]

The filter factor for a 25A should be 8x.

 

[Old-N-Feeble]

I shoot 400. It's 25a the website says.

What 400 film? The manufacturer's instructions or their website often have filter factors that are pretty close... at least under most daylight conditions and subjects.

 

[cliveh]

I am going to start using filters and was wondering if you expose the image any differently then what the meter tells you with a red filter? The one I will be using is a Hoya HMC.

May I ask what subjects you are photographing using a red filter and what you hope to achieve? This will help us give you good advice.

 

[LifeIn35mm]

May I ask what subjects you are photographing using a red filter and what you hope to achieve? This will help us give you good advice.

Rally cars. I would like to have more contrast.

 

[LifeIn35mm]

May I ask what subjects you are photographing using a red filter and what you hope to achieve? This will help us give you good advice.

I also photograph people. I would like more contrast on this too and darker skies.

 

[LifeIn35mm]

What 400 film? The manufacturer's instructions or their website often have filter factors that are pretty close... at least under most daylight conditions and subjects.

I will be sure to check out Ilford's site.

 

[Regular Rod]

If the filter is marked 8x then take the 400 ISO and divide it by 8 to get the ISO to set your hand-held meter at, i.e. 50 ISO.

So if your meter reading gave you an exposure for your rally cars of 1,000th of a second @ f6.8 then you will be needing 125th of a second @ f6.8. My meter is fairly simple so, when using a filter, I just change the ISO to the recalculated ISO and read the meter in the usual way and use the indicated exposure. It saves me from the ordeal of mental arithmetic...


RR

 

[Old-N-Feeble]

Filters don't add or reduce contrast. They only darken certain colors more than others.

 

[pentaxuser]

If it is shots like these with a white car I might not bother as the real subject, the car, being white shows up well.

A red lightens its own colour and related colours such as pale yellow grass so if the car is white then a red might lighten the grass as well and get it closer to the white car which is the opposite of what I think you are trying to achieve.

A filter won't alter the contrast in the sense that a higher grade of paper or a higher grade used with VC paper will alter contrast. However if it was a green car then a red will lighten the straw coloured grass slightly while darkening the green car so creating contrast between the car and the grass.

It is worth getting a book on filters or a general photography book where you will see examples of what each filter does to the same scene.

pentaxuser

 

[LJH]

I would suggest looking at your exposure/development/printing regime long before going to a filter.

Even if you decide to look at filters, I would not suggest starting with a red filter. Aside from the impact of a red filter on total transmitted light (i.e. in your case, shutter speed), you need to understand how a red filter effects shadows. I'd do a lot of reading before buying a red filter....

 

[Sirius Glass]

If using an in-camera TTL meter and the filter is attached, just meter and shoot. If using a hand-held meter, meter normally (without the filter in front of the meter) and open 3 stops to account for the filter.

That is what I do.

 

[pbromaghin]

For the skies you might want to try a polarizing filter. This works best when facing at right angles to the sun. You might be surprised to see what else it does to surrounding surfaces.

 

[cliveh]

I would suggest looking at your exposure/development/printing regime long before going to a filter.

Even if you decide to look at filters, I would not suggest starting with a red filter. Aside from the impact of a red filter on total transmitted light (i.e. in your case, shutter speed), you need to understand how a red filter effects shadows. I'd do a lot of reading before buying a red filter....

Good advice.

 

[LifeIn35mm]

Filters don't add or reduce contrast. They only darken certain colors more than others.

I thought that they did this. Am I wrong?

 

[LifeIn35mm]

I like the darker looks to images.

 

[Dr Croubie]

I thought that they did this. Am I wrong?

Red increases contrast, yes. But not directly and not always, only in scenes like this where it darkens the blue.
Where do you want the increased contrast? On that original shot on the first page, I saw no sky, it was just washed-out, I presume grey cloudy? Not much you can do about that with a filter.
What colour was the grass? You can darken that with a filter. Green grass will go darker with a red filter, yellow grass will go darker with a blue filter.

You can always underexpose and push, that'll get rid of all your shadow detail, increase contrast, and make it 'look darker'.

 

[pbromaghin]

Buy yourself one each green, blue, yellow, orange, red , polarizing or whatever filter and try them all out on more than one scene. Try to vary the scenes as much as possible. Put the camera on a tripod and take a shot with each one. Maybe also take a color shot with another camera for reference. I'm just learning about filters right now too, and I like to carry a couple in my pocket and just look through them now and then to get some idea of what they do.

 

[pentaxuser]

You are not wrong. That's a good example you posted of what a red does but you'll note that the red filter lightens the wheat/corn compared to the "no filter" shot and in the case of the car it would reduce contrast or as I thought you meant the differentiation between the car and its surroundings.

Great for skies but have a good look at what might happen to other colours in the scene before attaching the red.

If it is better to leave the colour difference as it is without a filter then a polariser will work much better than a red

A polariser darkens skies without actually altering any colours.

At some stage a set of filters will prove useful and if like me, in my "early days" of B&W photography, you have a "itch" to try filters then get a set and try them all out on scenes and note what happens

It's fun and you'll learn a lot.

pentaxuser

 

[LifeIn35mm]

Red increases contrast, yes. But not directly and not always, only in scenes like this where it darkens the blue.
Where do you want the increased contrast? On that original shot on the first page, I saw no sky, it was just washed-out, I presume grey cloudy? Not much you can do about that with a filter.
What colour was the grass? You can darken that with a filter. Green grass will go darker with a red filter, yellow grass will go darker with a blue filter.

You can always underexpose and push, that'll get rid of all your shadow detail, increase contrast, and make it 'look darker'.

It was actually just dust covering the sky from the car kicking it up. But still you can't do much for that anyway. I will do some research on underexposing and pushing.