Filters Drive Me Crazy

Don Wallace said:

I have in my hand right now a b+w orange filter (040 - or perhaps you know it by some other number or letter) and written on the ring is "4x" which I am guessing is the filter factor. This means that I open up by two stops.

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B+W quote filter factors by how much extra exposure you need to allow - and show it rather neatly (IMO) on the inside of the filter ring

As you correctly say 4X = 2 stops

Almost every filter manufacturer gives this info in different ways - but each to their own

I find it a lot easier to stick with one Filter Manufacturer for this reason - saves confusion towards the end of the day when mistakes start to creep in.

Filter Factors are not an exact number - there are too many variables to make a hard and fast fixed value - but they are a good guess and tend to be on the safe side (ie extra exposure)

Martin

Filters are fun, but nearly always impractical in what I shoot. I prefer 100 speed film and filters KILL the light so horrificaly that you need a tripod for evey shot.

keithwms said:

Among these factors, what is important and is usually forgotten is that the cell in the meter has a sensitivity curve something like this...

http://www.cs.brown.edu/people/tld/courses/cs148/02/images/wavelength.gif

...and the deep red / IR stuff is cut out by a hot mirror over the cell. So there's no guarantee that the cell's response looks at all like your film's response curve!

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Keith

I'm interested. Where did you get this curve? What ceel type does it reflect? Is there more?

Doremus Scudder said:

Ralph,

I think we are really saying the same thing.

www.DoremusScudder.com

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Doremus

We only differ in one point.

I recommend against metering through colored filters, because in my tests it confused the meter and gave wrong exposure recommendations. Having done this with several meters, I know that some meters are better than others, but none performed well enough to recommend metering through filters. Normal metering plus filter factor gave better exposures in every case.

Hi Ralph, it's a typical silicon photodiode response. The CdS cells have less IR response but are nevertheless peaked in the red, as I recall.

Just to throw in one more variable I don't think has been mentioned; the time of day and/or smog and/or altitude. Well, more than one more variable. Early and late the light is much 'warmer', smog does weird things, and as I remember at high altitudes the light gets really blue. So I don't think filter factors are going to be very exact or fixed. Experience and bracketing seem to me the best way to go, whether one reads through a filter with a meter or uses the manufacturers number. Both in my experience get usable results, but often conditions are such that a bracket is in order.

Thanks a lot, as usual, for the great information and discussion. I went out and shot two rolls of 120 as follows:
- I metered the scene without any filters to determine the exposure
- I shot one frame with this exposure
- I shot the next frame with a filter, adjusting the exposure according to the filter factor
- I used my spotmeter to measure an area of sky with no clouds
- I then measured the same area through the filter and adjusted my exposure by the this difference, e.g., 1/3 stop difference with my yellow filter, as opposed to the full stop indicated by the filter factor
- I shot a frame with this adjustment

I developed both rolls and will look at them carefully tonight or tomorrow night.

And now for a related story. I have been getting streaks and blotches on some of my 120 negatives recently, including the two test rolls I just shot. Just before I posted this, I checked out APUG for some advice, and lo and behold, I found a great thread started by Thomas (who also contributed here) and I am now pretty confident that I will have that problem licked too.

APUG is the best. I have to renew my membership!

Ok, it is time for the obvious.

I have two Nikon slrs and a Hasselblad. All three have built in TTL meters, well the Hasselblad has the PME prism, and whenever I use a polarizer or a filter I am metering through the filter. Suprise, surprise, surprise! All the exposures are properly corrected for the filters and I never have to worry about the exposure compensation.

:munch::munch::munch::munch::munch:

Steve

Don Wallace said:

Thanks a lot, as usual, for the great information and discussion. I went out and shot two rolls of 120 as follows:
- I metered the scene without any filters to determine the exposure
- I shot one frame with this exposure
- I shot the next frame with a filter, adjusting the exposure according to the filter factor
- I used my spotmeter to measure an area of sky with no clouds
- I then measured the same area through the filter and adjusted my exposure by the this difference, e.g., 1/3 stop difference with my yellow filter, as opposed to the full stop indicated by the filter factor
- I shot a frame with this adjustment

I developed both rolls and will look at them carefully tonight or tomorrow night.

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Very good, but I wish you had done this with a red filter too. The yellow filter makes little difference. Take a look at the diagram Keith posted. It explains why. The meter 'see's all this red light, and the film does not.

Sirius Glass said:

Ok, it is time for the obvious.

I have two Nikon slrs and a Hasselblad. All three have built in TTL meters, well the Hasselblad has the PME prism, and whenever I use a polarizer or a filter I am metering through the filter. Suprise, surprise, surprise! All the exposures are properly corrected for the filters and I never have to worry about the exposure compensation.

:munch::munch::munch::munch::munch:

Steve

Click to expand...

Of course it will, with a pol-filter. Try this with a red filter and be prepared for a disappointment.

Not only that, try observing the meter readings as you rotate the polarizer. Bet you dollars to donuts that the reading changes as the amount of polarization varies. The difference usually doesn't add up to much, maybe 1/2 stop variance. Still, you have to ask, which reading is the "correct" reading?

RalphLambrecht said:

Of course it will, with a pol-filter. Try this with a red filter and be prepared for a disappointment.

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The only disappointment that I have had with the red filter when I have meter this way, is that the composition still needed some improvement.

See above for orange, yellow, and green.

Is there a filter that will improve the composition just as the shutter is being fired?

Steve

Sirius Glass said:

The only disappointment that I have had with the red filter when I have meter this way, is that the composition still needed some improvement.

See above for orange, yellow, and green.

Is there a filter that will improve the composition just as the shutter is being fired?

Steve

Click to expand...

No need. Your meter seems to do it all.

Sirius Glass said:

Is there a filter that will improve the composition just as the shutter is being fired?

Steve

Click to expand...

Yes, Harrison & Harrison.
They pulled it from the market when they began to get complaints that one picture pretty much looked like another.

So, I got a bunch of filters...

People on eBay often sell cameras with filter sets. My recent purchase of a Fujica ST605n came with a stack of 49mm filters, and recalling this thread, I decided to test them and show the results. Here sre the results:

http://www.wolfeyephoto.com/BW_Filter_Effects/filters.htm

Wolfeye,

Now please repeat the experiment with two subjects.

• Sky with clouds
• Portrait close up

Then you will be able to see what filters can really do.

Steve