No more excuses about high ceilings and bounced flash

PacAce wrote in post #4910194
If there is not significant different in the intensity of the light among the different head focal length settings, then there should be no difference in the quality of light either.

Thank you for that little challenge, Leo, because it occured to me that I never really tested the theory.

So here goes:
Serving fork, white paper on the dining room table.
Camera on tripod about 5 1/2 feet high, 580EX II aimed straight up, about 2 feet below the 8 foot ceiling.

This shot with the flash head zoomed to 105mm

Curtis N wrote in post #4910503
Thank you for that little challenge, Leo, because it occured to me that I never really tested the theory.

So here goes:
Serving fork, white paper on the dining room table.
Camera on tripod about 5 1/2 feet high, 580EX II aimed straight up, about 2 feet below the 8 foot ceiling.

This shot with the flash head zoomed to 105mm
[]http://performancephot​o.smugmug.com …/254102911_Nwrj​2-M.jpg[/]

This shot with the flash head zoomed to 14mm
[]http://performancephot​o.smugmug.com …/254102940_F6CS​t-M.jpg[/]

When you bounce the flash, you're turning the ceiling into a softbox.
Do you want a big softbox, or a little one?

1) I thought we were talking about a 26 ft high ceiling.
2) If not, then tell me what the incident meter reading was for each of those shots (I assume you shot them both in manual mode with the same power setting).

Hey Curtis which pic do you like better? I find the second pic more appealing (less shadow and warmer look) but the first pic has certainly more detail (which you don't lose on the highlights).

Well this thread began talking about a 26 foot ceiling. Regardless of the ceiling height, the flash head zoom setting will affect the size of the hot spot on the ceiling, which becomes the apparent light source. This affects the characteristics of the shadows produced.

To be honest, it wasn't easy to find a suitable subject to demonstrate the differences. And I suspect those differences are usually not going to be noticeable. Seriously, I think we all have more important things to worry about while shooting than how to zoom the flash head. But I did want to illustrate the concept.

The 105mm shot metered at f/11 7/10, the 14mm shot metered at f/11 (ISO 400). Given the angles involved, I figure this 2/3 stop difference is related to the direct reflection from the ceiling that you alluded to earlier. Zooming to 105mm put all the light in just the right spot for that to occur.

Curtis N wrote in post #4910629
The 105mm shot metered at f/11 7/10, the 14mm shot metered at f/11. Given the angles involved, I figure this 2/3 stop difference is related to the direct reflection from the paper that you demonstrated earlier. Zooming to 105mm put all the light in just the right spot for that to occur.

...thereby illustrating my point made in message #21, "... the 'normal' GN, which I used in my analysis, becomes the 105mm GN...157 goes up to 191...and you improve output by only 0.5EV"

telles75 wrote in post #4910567
Hey Curtis which pic do you like better? I find the second pic more appealing (less shadow and warmer look) but the first pic has certainly more detail (which you don't lose on the highlights).

Actually, I like the one with the shadows better. It gives some depth to the image and helps show the curvature of the fork.

But that's just me. I'm certainly no pro at small product shots.

Curtis N wrote in post #4910664
Actually, I like the one with the shadows better. It gives some depth to the image and helps show the curvature of the fork.

But that's just me. I'm certainly no pro at small product shots.

I like shot #1 shadonwing better, if there was a white object that could have been seen in the reflection of some of the shiney curved surfaces of the fork. Combines the characteristics of both shots into one.

Wilt wrote in post #4910657
...thereby illustrating my point made in message #21, "... the 'normal' GN, which I used in my analysis, becomes the 105mm GN...157 goes up to 191...and you improve output by only 0.5EV"

I think we'll have to agree to disagree on that. I think it's a lot more complicated. There are direct reflections from both the ceiling and the paper that will sometimes come into play, as Leo demonstrated.

I suspect I could aim the flash somewhere else and come to a different conclusion on flash power, but like I said, I'm done measurebating on this topic.

You got a flash unit and a meter?

Curtis N wrote in post #4910695
I think we'll have to agree to disagree on that. I think it's a lot more complicated. There are direct reflections from both the ceiling and the paper that will sometimes come into play, as Leo demonstrated.

I suspect I could aim the flash somewhere else and come to a different conclusion on flash power, but like I said, I'm done measurebating on this topic.

You got a flash unit and a meter?

A lot more complicated? Yes, that I agree with whole heartedly. Where you bounce the flash relative to the location of the subject can make a BIG difference in the outcome of the resulting image.

Curtis N wrote in post #4910695
I think we'll have to agree to disagree on that. I think it's a lot more complicated. There are direct reflections from both the ceiling and the paper that will sometimes come into play, as Leo demonstrated. ...You got a flash unit and a meter?

I do not disagree that the topic is quite complex. OTOH, your test and my earlier statement, both seem to prove that -- in some circumstances -- the zoom head of the flash does have a direct impact on flash brightness on the subject of about 0.5 - 0.7 EV ...but sometimes no difference, too!

I just need to find a place with a nice high ceiling to practice measurbation~ TMR Design and I have been involved in some measurbation of our own, regarding flash output and color balance; we'll have to wait for him to publish our resuts!

Wilt wrote in post #4910745
I do not disagree that the topic is quite complex. OTOH, your test and my earlier statement, both seem to prove that -- in some circumstances -- the zoom head of the flash does have a direct impact on flash brightness on the subject of about 0.5 - 0.7 EV!

I just need to find a place with a nice high ceiling to practice measurbation~ TMR Design and I have been involved in some measurbation of our own, regarding flash output and color balance; we'll have to wait for him to publish our resuts!

I agree with you about that, too, assuming that the flash is pointed such that the direct reflected light falls on the subject. If that's not the case and the subject is illuminated mostly by secondary bounced light, i.e. bounced off walls, floor, etc. after it's initially bounced off the ceiling, then zoom setting may not matter.

Zoom setting does matter, Curtis's fork test just proved it. We weren't discussing quality to begin with just amount or quantity of light. I don't know how the gym test was at all relevant. If you think about how it was set up, I'm not at all surprised at how it turned out. Look at the fork shot however, which focal length is putting more light on the fork? It is the 105mm setting and remember we're not at all talking about softness or quality. The 105 setting put .7 of a stop more light on the fork and table. Is this because the angle of incidence and angle of reflectance are the same? I believe so and as far as I'm concerned Curtis proved it with these shots.

I realize, however, that this only proves a theory and may not be a practical way to shoot. If using ceiling bounce would be a better idea to use a wider than maximum focal length, regardless. I guess lighting a larger area with softer light would would be best and remembering, if a people shot, to avoid raccoon eyes.

Here are two post on the subject that may help clear things up as far as the fork.

http://strobist.blogsp​ot.com …it-21-apparent-light.html

From the above link (a little less than half way down, right above the flash against wall shots)

http://strobist.blogsp​ot.com …2-specular-highlight.html

From the above link (about a 1/6 the way down)

I suggest 1/8000 sec, f/22, ISO 100!

Some info on how distance affects flash & incandescent fill exposure:
Fill light at sunset

Thanks for this thread, Curtis!