Andrei
6th of July 2001 (Fri), 13:13
I've found it very useful for flash photography. I understood, why we should not shoot with Flash WB.
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Hi, Chris:
I addressed this issue about 6 weeks ago with a professional photographer who was asking similar questions. Please review the following response and let me know if it answers your questions:
Hi, Mike:
Thanks for sending in the images. I've had a chance to study them, and I've also performed my own tests using one of our sample D30s with a 550EX.
Based on what I can see and how I interpret our technical information from Canon Inc. in Japan, no useful purpose will be served by sending in Bruce's camera for repair or replacement.
Don't get me wrong: There's no doubt that all of the test photos shot on the Flash white balance setting (including mine, yours and Bruce's) are off-color. And it's also true that the photos shot on Auto white balance appear to be much better.
I'm pretty sure I've figured out why this is happening, and also what Bruce should be doing to ensure consistent results for his studio flash work, no matter whether he's using his Elinchrom strobe or the 550EX. Here's the scoop:
Auto white balance with the D30 is measured directly from a portion of the image data corresponding to the partial metering area indicated by the circle in the center of the focusing screen. When the target is a gray card, as it was with Bruce's sample photos, the D30 achieved an excellent, neutral color balance. Your photo of the wall map was also predominantly neutral in the central portion of the picture area, and the AWB shot was consequently very neutral as well.
On the other hand, the preset white balance settings are all keyed to specific color temperatures, as follows:
Tungsten: 3200K
Fluorescent: 4000K
Daylight: 5500K
Flash: 5900K
Cloudy: 6000K
These settings can be calibrated by the Service Dept., but no matter where they end up, they're always going to be fixed values. By contrast, Auto white balance is variable anywhere between 4000K to 7000K, which is what allows the resulting photos to be so perfectly balanced when a neutral target is used.
Based on this information, we can come to a couple of conclusions: First, the D30's flash white balance is only going to be accurate when the color temperature of the flash is at or very near 5900K, which is a little bit higher (or cooler, depending on your point of view) than the 5500K setting produced by the 550EX. Without the chance to speak directly with Canon Inc. R&D staff, my guess is that they selected 5900K for the flash white balance setting because they figured that studio strobes on average would be slightly cooler than daylight. But this is obviously going to vary case by case, and there are all sorts of other variables involved too, like potential color contamination from ambient lighting, or using a bounce reflector that isn't neutral, etc. Using Daylight white balance (as I recommended the other day) instead of Flash white balance, is one way of warming up the color with flash photos, but it's still subject to the variables mentioned above because it is based on a fixed color temperature value.
The second conclusion is that Auto white balance would appear to be a better choice for Bruce, except for one thing: I'm pretty sure that most of his real photos aren't going to contain gray cards. This is where the D30's Custom White Balance setting comes in. It has the same variable color temperature feature as AWB, except that it covers a range from 2000K to 10000K instead of 4000K to 7000K. In order to use CWB, Bruce can take one test shot with his gray card placed in the center, and then use the D30's CWB menu setting to register that value and use it for as many shots as required. This should solve the problem.
Please pass this information along to Bruce, and let me know if it helps.
Best Regards,
Chuck Westfall
Manager/Technical Information Dept.
Camera Division/Canon U.S.A., Inc.
---------------------
Hi, Chris:
I addressed this issue about 6 weeks ago with a professional photographer who was asking similar questions. Please review the following response and let me know if it answers your questions:
Hi, Mike:
Thanks for sending in the images. I've had a chance to study them, and I've also performed my own tests using one of our sample D30s with a 550EX.
Based on what I can see and how I interpret our technical information from Canon Inc. in Japan, no useful purpose will be served by sending in Bruce's camera for repair or replacement.
Don't get me wrong: There's no doubt that all of the test photos shot on the Flash white balance setting (including mine, yours and Bruce's) are off-color. And it's also true that the photos shot on Auto white balance appear to be much better.
I'm pretty sure I've figured out why this is happening, and also what Bruce should be doing to ensure consistent results for his studio flash work, no matter whether he's using his Elinchrom strobe or the 550EX. Here's the scoop:
Auto white balance with the D30 is measured directly from a portion of the image data corresponding to the partial metering area indicated by the circle in the center of the focusing screen. When the target is a gray card, as it was with Bruce's sample photos, the D30 achieved an excellent, neutral color balance. Your photo of the wall map was also predominantly neutral in the central portion of the picture area, and the AWB shot was consequently very neutral as well.
On the other hand, the preset white balance settings are all keyed to specific color temperatures, as follows:
Tungsten: 3200K
Fluorescent: 4000K
Daylight: 5500K
Flash: 5900K
Cloudy: 6000K
These settings can be calibrated by the Service Dept., but no matter where they end up, they're always going to be fixed values. By contrast, Auto white balance is variable anywhere between 4000K to 7000K, which is what allows the resulting photos to be so perfectly balanced when a neutral target is used.
Based on this information, we can come to a couple of conclusions: First, the D30's flash white balance is only going to be accurate when the color temperature of the flash is at or very near 5900K, which is a little bit higher (or cooler, depending on your point of view) than the 5500K setting produced by the 550EX. Without the chance to speak directly with Canon Inc. R&D staff, my guess is that they selected 5900K for the flash white balance setting because they figured that studio strobes on average would be slightly cooler than daylight. But this is obviously going to vary case by case, and there are all sorts of other variables involved too, like potential color contamination from ambient lighting, or using a bounce reflector that isn't neutral, etc. Using Daylight white balance (as I recommended the other day) instead of Flash white balance, is one way of warming up the color with flash photos, but it's still subject to the variables mentioned above because it is based on a fixed color temperature value.
The second conclusion is that Auto white balance would appear to be a better choice for Bruce, except for one thing: I'm pretty sure that most of his real photos aren't going to contain gray cards. This is where the D30's Custom White Balance setting comes in. It has the same variable color temperature feature as AWB, except that it covers a range from 2000K to 10000K instead of 4000K to 7000K. In order to use CWB, Bruce can take one test shot with his gray card placed in the center, and then use the D30's CWB menu setting to register that value and use it for as many shots as required. This should solve the problem.
Please pass this information along to Bruce, and let me know if it helps.
Best Regards,
Chuck Westfall
Manager/Technical Information Dept.
Camera Division/Canon U.S.A., Inc.