Filter Factors for B&W

[dustym]

What if any does a filter factor affect your DOF in a landscape photograph in lighting conditions that may be pushing your film to its failure limit, for example you may want cloud definition but may have to forgo definition in in your ground level scene oir a least try and equalise to a degree , or have I not yet grasped the filter idea yet.For instance I have read a few articles which favour an orange filter over red for landscape as it yields only a factor of 2 stops over the basic three for red and the use of a polarising filter for white cloud definition.

Any help or comments would be greatly received over this confusing matter for me

 

[photobackpacker]

Hi Dusty:

It depends on your exposure strategy. If when you mount a filter, you open up your aperture to compensate for loss of light, your DOF is diminished. If, on the other hand, you compensate with longer exposure, you have negated that impact.

In my personal use, I don't think in terms of reduced DOF - I become aware of subject movement from wind. There are times when I cannot execute the picture I would like to shoot because the movement of leaves, clouds or impact of wind on the tripod mounted 4X5 will not allow the exposure needed for the shot.

 

[marktweedie]

The filter won't affect depth of field unless the reduced amount of light entering the camera forces you open up your aperture (e.g. if you need for some reason to maintain your shutter speed.) The filter factor merely indicates how much less intense the light becomes once it passes through the filter. Hope that helps.

 

[dustym]

So if the scene allows compensate on shutter speed and maintain your apeture for the DOF, which landscape allows you to do unless you have moving elements in the frame which may cause an unwanted effect.

 

[Dave Parker]

So if the scene allows compensate on shutter speed and maintain your apeture for the DOF, which landscape allows you to do unless you have moving elements in the frame which may cause an unwanted effect.

Yes, normally this is true, DOF is a product of aperture adjustment, in the normal sense, if I needed to maintain a certain DOF, then adjust shutter speed to compensate for the filter factor, this will result in a longer exposure and if something were to move through the frame or the wind blew the grass in front of your lens, you would see that effect.

Dave

 

[Lee Shively]

The filter factor is actually a number divided into the exposure index of the film to determine the final exposure. This was handy when using a handheld meter. For instance, a filter factor of 4x used with ISO 400 film would mean you would adjust your handheld meter to read 100 instead of 400. For those of us who are mathmatically challenged, that gets confusing. It's also unnecessary (and sometimes inaccurate) when using the cameras build-in meter and reading through the filter.

You have the right idea, since you are determining the increase in exposure in stops instead of filter factors. If you're using a handheld meter, it's good to make a chart of the exposure increase of each filter you use and attach it to the meter.

When using a filter that increases exposure beyond the recommended range, you have to compensate for this by increasing the exposure. If, for instance, a certain film has an exposure index of 400 at shutter speeds from 1/2000 to 1/2 second, you will have to increase exposure if you use a shutter speed longer than 1/2 second. This amount of compensation varies over the period of exposure. The exposure compensation is usually on the information packed with the film or it can be found on the manufacturer's website.

If I'm understanding your question correctly, it has to do with this compensation in exposure. It can be due to using a filter or simply due to the low level of the light. Your depth of field will be affected only if you compensate by opening the aperture of the lens as opposed to using a slower shutter speed. Once you're into shutter speeds of 1/2 second or slower, you're out of the realm of stopping much action so increasing exposure by adding time is usually a reasonable act.

You also indicate you "may have to forgo definition in your ground level scene or at least try and equalise to a degree". You should consider a graduated neutral density filter. This filter is made specifically for such purposes. With the graduated filter, you make your meter reading of the "ground level" subject you indicated and use the filter to hold back the brighter sky. It's an in-camera way of burning in large bright areas within the frame.

Jeez...I've taken your straightforward question and babbled on too long. I hope my response doesn't confuse you further.

 

[Dave Parker]

I thought we were talking about DOF and Filter Factors?

 

[Lee Shively]

Photography, especially black and white photography, is a process. Each step in the process affects each subsequent step. The filter factor has no direct effect on depth of field but it does impact exposure. How the compensation in exposure is handled will affect depth of field.

The original question noted the poster was having difficulty grasping the use of filters and my response was intended to help. If it came across as off-topic or confusing, I apologize. But I don't think it's possible to address one step in the photographic process without considering other factors. Otherwise you're just exposing film and hoping for the best.

 

[Dante Stella]

Published filter factors are overstated

The two and three stop factors for orange and red are fictitious and designed around reproducing a middle grey tone (as far as I can tell) - start with ZERO filter factor and work your way up until your process gives you the clouds you want. You may find the factor so small that it involves no DOF loss.

What if any does a filter factor affect your DOF in a landscape photograph in lighting conditions that may be pushing your film to its failure limit, for example you may want cloud definition but may have to forgo definition in in your ground level scene oir a least try and equalise to a degree , or have I not yet grasped the filter idea yet.For instance I have read a few articles which favour an orange filter over red for landscape as it yields only a factor of 2 stops over the basic three for red and the use of a polarising filter for white cloud definition.

Any help or comments would be greatly received over this confusing matter for me