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04-10-2007, 03:28 AM   #1
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White Balance: A Poor Man's Exposure Disc

Following up on dmdctusa's pondering in another thread, I filled an idle two minutes at work today by making an exposure disc out of a coffee filter.

Materials:

A 52>58 step-up ring that I'm not currently using
A Skylight 1A filter that was serving merely as a front element protector
A white coffee filter

Tools:

A ballpoint pen
A pair of scissors


I cut the filter and laid it out flat. Then placed the step-up ring on it and traced around it with the pen in order to get the approximate size. Then I cut it out, test-fitted it, and trimmed it down just a bit to fit inside the step-up ring. After that, it was just a matter of screwing the skylight filter down over it.

It doesn't give 100% perfect results, but I think that may be because the skylight filter only looks 100% clear. I tried it again with a regular lens guard filter and it works just fine.

I'm so glad I didn't give in to the urge to plunk down a hundred bucks for an ExpoDisc the first time I learned about them.

04-10-2007, 04:37 AM   #2
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QuoteOriginally posted by Mike Cash Quote
Following up on dmdctusa's pondering in another thread, I filled an idle two minutes at work today by making an exposure disc out of a coffee filter.

Materials:

A 52>58 step-up ring that I'm not currently using
A Skylight 1A filter that was serving merely as a front element protector
A white coffee filter

Tools:

A ballpoint pen
A pair of scissors


I cut the filter and laid it out flat. Then placed the step-up ring on it and traced around it with the pen in order to get the approximate size. Then I cut it out, test-fitted it, and trimmed it down just a bit to fit inside the step-up ring. After that, it was just a matter of screwing the skylight filter down over it.

It doesn't give 100% perfect results, but I think that may be because the skylight filter only looks 100% clear. I tried it again with a regular lens guard filter and it works just fine.

I'm so glad I didn't give in to the urge to plunk down a hundred bucks for an ExpoDisc the first time I learned about them.
I do not have a 1A filter here to check but I assume they have a slight pinkish cast from what I found on a quick Google search.
As you found with your first test the setting the white balance is true ONLY if you mount a 1A filter for the following images - without this filter the images will be slightly cold as the white balance has been set to compensate for the faintly pinkish light that was measured through the filter.

As you found, this technique is best done with with a neutral protector or even cheaper a Pringles lid plus coffee filter or a Pringles lid alone in the days of their earlier translucent lids.

Rod
04-10-2007, 05:08 AM   #3
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Actually, there was an ever-so-slight bluish tinge...although it did perk up the saturation and make grass look nicer. If I hadn't been shooting the same scenes (outdoors) and comparing between AWB and the 1A I would have been hard pressed to tell the difference. It wasn't until near dusk (and again indoors) that the bluish tinge really stood out. Subsequent indoor tests with the lens guard filter showed that the skylight filter was definitely the culprit.

The really nice thing is that I can always unscrew the thing and use my step-up ring for its original purpose. Fortunately, it is a size that I don't have much use for right now, as most of my daily-use lenses are 49mm.

The really, really, really nice thing is the money I didn't spend in order to gain this neato functionality.
04-10-2007, 06:18 AM   #4
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Mike,

In my post re coffee filters, I did not mention the fact that I had a Heliopan UV filter on my 18-55. Since I always have a UV on all my lens, I didn't even notice that I had it on the camera when I tested. The 1A would definitely affect the WB slightly. I have not compared readings with and without the UV filter.

Further, I have re-thought the mounting method. I an going to take two same sized rings and remove the glass and and triy to force the thread of the outer ring to hold the flter in place. If the filter gets damaged it's at least field repairable. I will report back as soon as I find some really cheap old filters that I can destroy.

For the present, just holding the filter over the lens and filter (no shade) works fine for me.


Last edited by dmdctusa; 04-10-2007 at 06:21 AM. Reason: punctuation and spelling
04-10-2007, 09:57 AM   #5
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I think I'd try to force the thread of the outer ring to hold the filter before I removed the glass. That way if you find out it's physically impossible to sandwich the paper between the threads you won't have ruined a filter needlessly.

At any rate, thanks muchly for the inspiration you provided me in making this contraption. I can take the money I would have otherwise been tempted to put toward an ExpoDisc and use it for a KatzEye instead.
04-10-2007, 12:13 PM   #6
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why would you want to put the sheet in the filters? isnt it more convenient to just hold the white sheet up when you take the white balance instead of threading a filter on and off each time?

what am I missing?
04-10-2007, 03:02 PM   #7
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Hi Mike, Just trying to get into raw processing and see that one need not be concerned with white balance at all!! According to the authors of rawshooter essentials "....leave camera set to auto white balance"... Workes for me.
04-11-2007, 05:07 AM   #8
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QuoteOriginally posted by kmccanta Quote
why would you want to put the sheet in the filters? isnt it more convenient to just hold the white sheet up when you take the white balance instead of threading a filter on and off each time?

what am I missing?
Just speaking from the perspective of the particulars of my own personal use:

1. The filter contraption I rigged up has a larger diameter than the lenses I am using it with, so I don't thread it on at all. I just hold the glass side flat against the front of the lens.

2. Almost all my shooting is done from the cab of a tractor-trailer. When shooting to the side, I roll the windows down in order to have the glass out of the way. Something as light as a coffee filter is apt to blow around on windy days. The weight of the contraption prevents that.

I suppose there is also an aesthetic consideration, but that wouldn't really bother me. And people who would think nothing of a photographer holding some photographic-looking device up in front of their camera would be likely to ask why somebody is holding a coffee filter up. Answering the same question over and over again might get a little old.

And I think it is easier to hold the filter contraption up and get it firmly against the lens than it is to do it with the paper loose. Light coming in from the side would sort of defeat the purpose, I'm guessing.

04-11-2007, 07:30 PM   #9
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QuoteOriginally posted by db2 Quote
Hi Mike, Just trying to get into raw processing and see that one need not be concerned with white balance at all!! According to the authors of rawshooter essentials "....leave camera set to auto white balance"... Workes for me.
Hi db2:

As a raw shooter, I was going to make a similar post. However, with the resulting images-per-card ratio reduction, which in my case influenced me to get some more cards, it is not quite the cheapest answer :-)
04-11-2007, 07:41 PM   #10
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QuoteOriginally posted by SpecialK Quote
Hi db2:

As a raw shooter, I was going to make a similar post. However, with the resulting images-per-card ratio reduction, which in my case influenced me to get some more cards, it is not quite the cheapest answer :-)
Wait so design wise, how does this work?

You put essentially white paper infront of the lens and using the custom WB, you take the test shot against the light?
04-11-2007, 08:11 PM   #11
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QuoteOriginally posted by FotoPete Quote
Wait so design wise, how does this work?

You put essentially white paper infront of the lens and using the custom WB, you take the test shot against the light?
Hmm, you question does not follow from my quoted post, I don't think.

But, I'll give the only 3 answers I know of about WB.

1. Expodisk/coffee filters go against the front of the lens. Point toward the subject and use the custom function to set the WB. The expodisk will also ( I believe, and for $100, expect) provide the correct exposure. A coffee filter is iffy for the exposure value. You could test it and determine that perhaps 2 layers of filter gives the correct exposure, etc.

2. Using a large piece of white or gray paper to fill the frame, but away from the lens. It should have the same light as the subject, i.e, both in direct frontal sunlight. I would say never to shoot againt the light for this method.

3. RAW shooting allows you to adjust the WB or almost any other setting, such as contrast or sharpness, after the shot, in the conversion to jpg. It gives more flexibilty in adjustments and corrections, and because adjustments are before making a jpg and not after, image quality is arguably (and it is argued by some) better than editing lossly jpgs.

Sorry if I missed something simple :-)
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