Filter Factors

Jorge · Jan 6, 2003

Ok here is my problem, years back I had done testing with a color chart and each filter by exposing the film with the filter. From the negative of the color chart I picked the best "factor" that gave me a Zone V. So in the move I lost the color chart and I lost the list with the factors I had made.
Not having a way to test now I was following the reccommended factors with less than satisfactory results. So unpacking my old issues of View Camera I came accross about an article by Simmons about the filter factors and how Hutchins uses the "meter through the lens and add..." So I am wondering has anybody used this method?
I understand that meter cells are not color corrected, but I would like to know how close this method can take you to a correct exposure.

Donald Miller · Jan 6, 2003

I am unsure if you are working in color or black and white...but here is my experience. I have a Zone VI modified Pentax digital meter and I work exclusively in black and white. I always meter the scene through the filter with this meter and it is much more consistant, in my experience, then using filter factors. I don't know how an unmodified meter would react in similar circumstances. Good luck.

Regards,
Donald Miller

lee · Jan 6, 2003

my experience is that the unmodified and tbe modified give the same reading within acceptible margin of error. Like a third of a stop. I have tested this with several meters including my own.

lee\c

Jorge · Jan 6, 2003

But how about adding the "extra" factor Hutchings reccommends? for example from the article the chart indicates:

For a medium orange filter #16 meter through the filter and add 1 stop. Does that work?

SteveGangi · Jan 6, 2003

Maybe this is wrong, but Hutchings may have been talking about the effect filters have on objects that are shaded (and so have a bluer cast to them). Personally, I never used his adjustment factors since there is enough to remember already, and the changes to me would be so minor as to not be noticeable at least by me. It's easier to just meter through the filter, or use the generally accepted filter factors.

Les McLean · Jan 6, 2003

A few years ago I spent a couple of hours and a couple of rolls of 120 film testing my filters to determine my own factor. The procedure I used is as follows. I chose a landscape subject with a full range of tones and using my spotmeter metered and exposed for the shadows in my normal way with no filter in place. This negative is my reference. I metered the scene through the filter being tested and made a second exposure and then underexposed by one stop and over exposed by one stop. Obviously the last three exposures were made with the filter in place. I followed this procedure using 5 filters, red, orange, yellow,green and polariser. When the film was processed I selected the negative showing the shadow detail that matched the reference negative.
This method may not be the most scientific and does not take into account the effect that the filter has on the cells etc., but it works for me. If I replace a filter I carry out the same test on the new one.

Jorge · Jan 6, 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Les McLean @ Jan 6 2003, 01:27 PM)</td></tr><tr><td id='QUOTE'>A few years ago I spent a couple of hours and a couple of rolls of 120 film testing my filters to determine my own factor. The procedure I used is as follows. I chose a landscape subject with a full range of tones and using my spotmeter metered and exposed for the shadows in my normal way with no filter in place. This negative is my reference. I metered the scene through the filter being tested and made a second exposure and then underexposed by one stop and over exposed by one stop. Obviously the last three exposures were made with the filter in place. I followed this procedure using 5 filters, red, orange, yellow,green and polariser. When the film was processed I selected the negative showing the shadow detail that matched the reference negative.
This method may not be the most scientific and does not take into account the effect that the filter has on the cells etc., but it works for me. If I replace a filter I carry out the same test on the new one.</td></tr></table><span id='postcolor'>
That is a good test, at least you know you will get shadow detail.

bmac · Jan 6, 2003

Les, doesn't the polarizer transmit different amounts of light depending on the amount of rotation of the filter + direction of the light?

Les McLean · Jan 6, 2003

Brian,

Yes it does, well spotted I'll give myself a slap on the wrist for not making the point. I only use the polarising filter in B&W when I'm looking for a really dramatic sky so I combine red and polariser. Therefore when I test I set it to fully polarise the light and make sure that the sun is at rightangles to the camera to maximise the effect.

Ed Sukach · Jan 6, 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (lee @ Jan 6 2003, 07:29 AM)</td></tr><tr><td id='QUOTE'>my experience is that the unmodified and tbe modified give the same reading within acceptible margin of error.  Like a third of a stop.  I have tested this with several meters including my own.

lee\c</td></tr></table><span id='postcolor'>
The manufacturing tolerances applying to Photographic Light Meters are most probably the limiting factors here. Gossen only claims an accuracy of +/- 1/3 "stop" for their UltraPro.

The manufacturers do not provide easy access to that information. Many years ago, I calibrated a Honeywell "1 degree/ 21 Spot" meter (an attempt to use it in an industrial application) and after a monumental struggle, found that the manufacturing tolerance was only +/- 1/2 "stop".

Given all the variables in the process; film speed tolerance; shutter speed and aperature tolerances; and sundry others, I would not really be too concerned over *exact* exposure.

lee · Jan 6, 2003

HI Ed,
I agree that the light meter is just one step in the exposure chain. I tend to error in the + area anyway for black and white film.

lee

Nige · Jan 6, 2003

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Les McLean @ Jan 6 2003, 10:27 AM)</td></tr><tr><td id='QUOTE'>A few years ago I spent a couple of hours and a couple of rolls of 120 film testing my filters to determine my own factor...</td></tr></table><span id='postcolor'>
simple but practicle

Will try this soon.. thanks for the tip!

Aggie · Jan 7, 2003

Aggie · Jan 7, 2003

Jorge · Jan 7, 2003

Hey Aggie great help....so it does work? have you found out any gross errors? like say your negative was underpoxed by 1 or 2 stops, or does the system work close enough. I mean 1 stop to 1/2 stop error, who cares....but 2 stops would have me worried.

BTW I can tell you that the B+W filter factors are very unreliable. These are the filters I have and they consistently underxposed the image. I hate that, I rather overexpose and work in the darkroom than have that morass (emphasis on the last syllable) of featureless black.....

Aggie · Jan 7, 2003

Donald Miller · Jan 7, 2003

The problem that I have discovered for myself is that the meters as they are manufactured do not see in the same way that panchromatic film does. In fact they will tend to give evergreen (pine) tree foliage too little exposure. The reason is that the evergreen foliage radiates a great deal of IR radiation. The meter sees it but the film does not. At the other end of the extreme these same meters will tend to give red too great exposure. Which is all good once we determine that is what is happening. For instance if one were to place the aforementioned green foliage at a zone III placement with even a brand new meter the negative and consequently the print will be more akin to a I 2/3 placement. The modification that Zone VI did to the Pentax meters went a long way to solving this problem through the use of sharp cutting filters as well as UV and IR filters and baffling. I have used several meters over the years and have found nothing aside from the modified meters that sees light in the same way as the film does. For that reason if one were to meter through filters with a unmodified meter the result would probably not be as accurate as one would hope. This has all been verified in my experience.

Jorge · Jan 7, 2003

dn that is my feeling also, I think I am just going to go with Les's test. At $5 a shot for a 12x20 I cant be fooling around with " close but no cigar" methods.

dr bob · Jan 8, 2003

Many of my photographs require no filters but when I have had to use them I have found that my equipment (mainly a Mamiya C330f and a Speed Graphic) with TX, or HP5 (both rated at ISO 200) require at least one more stop increase than those listed in the Gordon Hutchings listings. Also, they do not seem to agree with the classical listings in general.

Anyone know what equipment and procedures were used by Hutchings in composing this listing?

There's nothing so satisfying as personal testing, providing you don't let it take over your life.

Truly, dr bob.

Aggie · Jan 8, 2003

Tom Duffy · Jan 13, 2003

Jorge,
I found that Gordon's recomendations are in line with my observed results. When I first got my zone VI pentax meter, I bought some 40.5 mm filters to mount on the spotmeter and metering through the filter, expecting, as per Picker, that my meter readings would be correct, using this procedure.

Empirically, I found my pictures using red, orange and yellow-green filter were under exposed by 2, 1 and 1.5 stops respectively. yellow meters accurately.

also be aware that this meter will underexpose by 1 to 2 stops when metering in tungsten light.

Take care,
Tom

Filter Factors

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