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01-17-2007, 07:52 AM   #16
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QuoteOriginally posted by NLAlston Quote
But let me ask a question: can the white lens cap, which came with my Tamron 18-200mm lens, be effectively used for the WB setting purposes?

I would not expect a lens cap to be very good for this purpose, because it's not large enough. It is my understanding that, when you set the white balance with a white card, you want to get the card to fill the exposure - so you're photographing nothing but white. I assume you're lens cap isn't big enough for that purpose. The ExpoDisc, by the way, is no bigger than your lens cap - it comes as a filter that you screw on to the front of the lens. But like a filter, it fills the exposure area completely. (It's not really a filter. After you set the custom WB, you remove the ExpoDisc to shoot your photo.)

I've seen an alternative method for dealing with white balance: take a test shot first in which your subject (if the subject is a person) actually holds the white card up while you photograph. This won't actually SET the white balance in the camera correctly, but it gives you a white reference point to use in post-processing. I've not tried this technique with a card, but I have occasionally used the eye dropper tool to identify the white balance, usually by clicking on someone's white shirt or something like that.

Will

01-17-2007, 08:41 AM   #17
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Thanks, Will.
01-17-2007, 09:35 PM   #18
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QuoteOriginally posted by WMBP Quote
I've seen an alternative method for dealing with white balance: take a test shot first in which your subject (if the subject is a person) actually holds the white card up while you photograph. This won't actually SET the white balance in the camera correctly, but it gives you a white reference point to use in post-processing. I've not tried this technique with a card, but I have occasionally used the eye dropper tool to identify the white balance, usually by clicking on someone's white shirt or something like that.
Nice tip! Thanks, Will!
01-22-2007, 08:39 AM   #19
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I've a question about a WB-issue that I am not sure may fit the topic. In low light situations with auto-focus on, on my kit lens coupled with the K100D, I seem to be unable to aquire white balance with af. The focus indicator blinks and the focus never finds the target. In other words I have to set manual focus before I WB.

The funny thing is that this only happens when I try to set WB. The focus fuctions normal when I try to shoot the subject. Do anyone else experience this issue?

If this is normal for a DSLR, please excuse me for asking.

01-22-2007, 09:03 AM   #20
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QuoteOriginally posted by maleek Quote
I've a question about a WB-issue that I am not sure may fit the topic. In low light situations with auto-focus on, on my kit lens coupled with the K100D, I seem to be unable to aquire white balance with af. The focus indicator blinks and the focus never finds the target. In other words I have to set manual focus before I WB.

The funny thing is that this only happens when I try to set WB. The focus fuctions normal when I try to shoot the subject. Do anyone else experience this issue?

If this is normal for a DSLR, please excuse me for asking.

No need to apologize - or I hope there isn't, because I myself have been asking a lot of basic questions here without apology. :-)

If you're using a white card (or the ExpoDisc) to set your custom white balance, you're basically taking a shot of something with little or no contrast in it at all. Remember, the white card is just a big pure white card. So auto-focus will indeed go crazy - no contrast to lock into. I'm not sure why the camera's don't automatically put the camera in manual focus mode when you take that shot for the purpose of setting a custom white balance, but they don't. SO you have to remember to do it yourself, just for 10 secs, then put it back to auto-focus if that's what you want.

Will
01-22-2007, 09:30 AM   #21
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In addition, WB must be done under conditions where a proper exposure can be acheived. Your low light condition might be at or near the camera/lens exposure limits and that might make WBing problematic.

WB, AF and the camera exposure meter all have different ranges of operation--usually the meter has the greatest range, followed by AF, then WB, but any can have a non overlapping end in their range.
01-22-2007, 09:34 AM   #22
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QuoteOriginally posted by WMBP Quote
The ExpoDisc, by the way, is no bigger than your lens cap - it comes as a filter that you screw on to the front of the lens.
I should correct a detail here. Contrary to what I said above, the ExpoDisc doesn't screw onto the lens's filter threads. You push it on to the lens just as if it were a filter, but the ExpoDisc has no threads itself, so you hold it in place by hand while you take your test shot. I find this a tad awkward. Before getting the ExpoDisc that I have now, I had an "ExpoCap" - same product, basically, but with a different attachment mechanism. The ExpoCap was more like a lens cap with spring thingies that pushed out when you put the cap in place and held it there. I liked that better than the ExpoDisc.

As I have noted already, the ExpoDisc is not cheap. Average cost per unit seems to be $100 or more. But it's actually a bit worse than it sounds. Because they are precisely sized - just like lens caps and filters - you may want to have one for every different size of lens you have. Perhaps the best bet is to get one that's too big and simply hold it over the smaller lens. At $100+ per unit, the ExpoDisc is too expensive for me to acquire one for every lens. I have tried mounting the lens that the ExpoDisc is properly sized for, setting the white balance, and then changing lenses. I can't think why that would not work. But the results were not as good as when I shoot with the lens I used to set the white balance.

Finally, this weekend while shooting basketball, I noticed that the custom white balance I set initially worked great for SOME of my shots but not all of them. It appears that the white balance was changing as I pointed the camera in different directions. That makes some vague sub-rational kind of sense to me. But it's leading me to the conclusion that the ExpoDisc might be most useful to portrait photographers and others who (a) want to get the WB absolutely right in the camera and (b) are able to set up their shots carefully and don't have to endure a whole lot of unpredictable changes to shot angles or lighting.

Click here to view two pairs of shots (= 4 shots total) that I took to test the ExpoDisc. I think the pictures demonstrate that ExpoDisc does do something good. Whether it's worth the price and trouble is a separate question. The link takes you to the first of a sequence of four photos in a gallery. Read the captions for the photos. The other pictures in this same gallery were test shots with my Pentax M F1.4 50mm and don't have anything to do with the issue of white balance.

Will

Last edited by WMBP; 01-22-2007 at 09:58 AM.
01-22-2007, 11:21 AM   #23
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Custom White Balance (WB) can be set using just anything not containing a color. The whole point in doing this is to get the correct, or nearly correct, colors straight out of the camera when shooting JPGs, or when extensive chimpin' is appropiate.
When shooting raw the WB doesn't matter as you adjust it in PP.

What can be used to set the custom WB? Anything white or non-colored grey. Make life easier for you and set the camera to accept just having the center of the picture covered when setting the WB manually.

A sheet of plain white office paper works well. The lid coming with Pringle can work as an expodisc (cheaper and you can eat those snacks also, people are seriously discussing if one taste or another of Pringles have different colors to the lid... ). A grey card is totally okey as long as you have enough light. If the camera complains try with a piece of white paper (or the backside of the Kodak Grey Card...).
Even better is to shoot raw instead and fix the color in the beginning of the developing process. Here is a nice guy helping me checking the light setup:


Maximum best is to use a Gretag Color Chart and calibrate the whole picture - but seriously, do you need it? Everything can be taken to an extreme... In the example above only the grey patch is used for adjusting the colors.

regards,

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