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-   -   Difference in incidence vs reflected (https://forums.steves-digicams.com/studio-lighting-flash-other-53/difference-incidence-vs-reflected-90618/)

crash331 May 23, 2006 9:40 PM

I just want to make sure I am getting this right. I just bought a Sekonic L-358 and it's giving different Fstops than my Rebel XT. To test it, I meter a scene that was almost 100% white. When I used the XT, it said I should take the picture for 1/5 seconds at F5.6. (very low light, sorry). This produced a histogram with a very sharp spike right in the middle of the histogram. The XT is trying to average the scene to 18%, right?

Now with the sekonic, I took a incidence reading, and it suggested that I was underexposing and it wanted me to make the shutter speed 1/2 a second at F5.6. When I look at the histogram on this image, the very sharp spike is almost all the way to the right. That means it didn't average the scene to 18%, it averaged the light falling on the scene to 18%, and therefore exposed the wall correctly.

Am I right in all of this, or do I need to do more studying?

ChrisDM May 24, 2006 9:38 AM

crash331 wrote:
Quote:


That means it didn't average the scene to 18%, it averaged the light falling on the scene to 18%, and therefore exposed the wall correctly.

That's right. The quote you made above states well the difference between reflective and incedent readings.

Reflective meters can be fooled, because different subject materials have different reflective properties. Incedent meters are more accurate because they simply measure the light falling on the subject, regardless of the subject's reflective properties.

BTW, I would highly recommend a book called "Light: Science and Magic" for getting a true understanding of light and how it relates to photography.

Chris M
www.imagineimagery.com


crash331 May 24, 2006 6:37 PM

Dude, If I could hug you,I would. I read part of this book several months ago at barnes and noble (I use that store like it's a library). I was going back to buy it the other day and it wasn't there and couldn't remember the name of it. Thank you so much!

ChrisDM May 31, 2006 4:53 PM

crash331 wrote:
Quote:

Dude, If I could hug you,I would. I read part of this book several months ago at barnes and noble (I use that store like it's a library). I was going back to buy it the other day and it wasn't there and couldn't remember the name of it. Thank you so much!
No prob. Yeah, that book is serious. If I ever grasp most of it, you could call me Dr Light...

Chris M
www.imagineimagery.com


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