Weekly Assignment #82: It's not the size...

Nikolai

There is a lot of talk about different flash diffusers. Some of them true, some are pure BS. This week you're going to put all this talks to the test and come out with your own opinion based on your own facts..

You would need a dedicated flash unit

To do this we going to build a set of very simplistic diffusers and then use some simplistic targets at different distances from the said diffusers. Naturally there will be a difference in luminosity (and probably noise), but we are not going to be concerned about it and will simply bring every test image to the approximately same general level of luminosity.

Here's just ONE possible suggestion how to do this testing. However you can go your own merry ways as long as the results are comparable.

1. Get 2 white foam boards (the ones that can stand by themselves) and 2 dark paper poster board.
2. Get camera on a tripod and a couple of chairs
3. Wait until it gets dark
4. Cut one dark poster board in half length-wise, another width-wise. Using scotch tape or some clamps attach both boards to one of the white ones in a way that there is a rectangular opening somewhere in the middle.
5. Using something like unbent large paper clips (and a scotch tape if you need it) attach a small opaque target (a business card or an index card) to the second foam board in a way that there is about 2-3 inches between the card and the board.
6. Put the chairs close to each other, put the foam board on them facing each other. Make sure there is no light-colored wall close to the back of the "aperture" board.
7. Put the flash close to the aperture board, its working surface facing the board (and away from the target)
8. Adjust your rectangular "poster aperture" that it only opens a white rectangular white space similar in size to the flash surface itself.
9. Focus your camera on the target in a way it can "see" the shadow that is created by the light reflected
10. Start taking pictures of the target and increasing the "reflector aperture" (don't forget to take notes). It can also be a good idea to take a picture of each aperture and then a picture of the target, thus making the whole thing self-documented. OR replace the targets (index/business cards) each time and write the conditions directly on them, this would be even better. Don't forget the notes of the flash intensity and ISO level - you would need to adjust those to keep with the distance...
11. Increase the distance between the boards twice. Repeat step 10.
12. Repeat step 11 until you're out of the room space.
13. Download the results to your computer and analyze the sizes of the shadows created.
14. Create a composite image by putting all your results in a matrix form (reflector opening size vs distance to target)
15. Make a post here with the said composite shot, few shots of the setup, project description and your thoughts of how the reflector size REALLY affects the shadow sharpness.
16. For the extra points make a few portraits of the same person at some limited selected number of "reflector size vs distance" combinations.

Clear as mud? :wink

Anyway: let's put those diffuser size myths to the test!

OffTopic

scratch Do you have a pic of this setup Nikolai? I've read through it four times and I'm just not getting it.

rofl

OffTopic

Never mind, I think I just understood what you were saying.

Nikolai

OffTopic wrote:

Never mind, I think I just understood what you were saying.

Yay!
The idea is to create a reliable correlation between the size of the light source, distance from the target and the shadow softness. Reflecting the flash from the "apertured" white foam board in an otherwise dark room gives you an easy yet very precise control over your light source size. Using a shoot-through diffiser is also possible, but much harder to setup, imho (god knows, I tried).
The suggested target structure mimics the distances commonly found in human faces.
HTH :-)

TexPhotog

Nikolai wrote:

Clear as mud?

Anyway: let's put those diffuser size myths to the test!

Sorry... I left my astrophysics in quantum nanomechanics phd at home... care to throw more mud on top of it... please.....

Nikolai

TexPhotog wrote:

Sorry... I left my astrophysics in quantum nanomechanics phd at home... care to throw more mud on top of it... please.....

The idea is to capture (in a consistent verifiable manner) the dependence of the shadow size and harshness on:
1) size of the light source, and
2) distance from the light source.
That's it...

Bayer-Z28

.......... ..........

OffTopic

If I'm understanding correctly, we are going to use one of the pieces of white foamboard to bounce our flash. We use the black posterboard (4 pieces) overlapped on the white foamboard to leave a white square showing, starting at the size of our flash head, then making it larger a few times (creating a larger bounce card/reflector/whatever you want to call it). Then move the bounce board further away from the target and repeat the process, etc. Your flashhead should be aimed at the white square opening, bounced onto the business card target that is 2-3 inches in front of the second white foamboard, and we need to document the shadow created by the target (on the second white foamboard) at each size and distance combination. Is that correct Nikolai?

Just haven't done it yet because I don't have the supplies...

Nikolai

OffTopic wrote:

Is that correct Nikolai?

100%
The only minor correction is that I think it's easier to move the target from the flash/bouncer assembly and have assembly rest in place. YMMV, of course.

TexPhotog

OffTopic wrote:

If I'm understanding correctly, we are going to use one of the pieces of white foamboard to bounce our flash. We use the black posterboard (4 pieces) overlapped on the white foamboard to leave a white square showing, starting at the size of our flash head, then making it larger a few times (creating a larger bounce card/reflector/whatever you want to call it). Then move the bounce board further away from the target and repeat the process, etc. Your flashhead should be aimed at the white square opening, bounced onto the business card target that is 2-3 inches in front of the second white foamboard, and we need to document the shadow created by the target (on the second white foamboard) at each size and distance combination. Is that correct Nikolai?

Just haven't done it yet because I don't have the supplies...

You mean something like this???

Picture1.jpg

OffTopic

TexPhotog wrote:

You mean something like this???

Picture1.jpg

Almost...reverse the positions of the business card and the second white board so the reflected light creates a shadow of the business card onto the second white board. Your camera would be off to the side of the reflector board facing in the opposite direction that your flash is facing. Unless I'm missing something, your flash has to be off camera.

I can picture in my head exactly what Nikolai wants us to demonstrate, but I only have one (clean) white board right now and no black posterboard. I'll see if I can buy some boards tomorrow.

I think this exercise is going to be confusing for anyone who hasn't worked with off camera lights before.

Nikolai

OffTopic wrote:

Almost...reverse the positions of the business card and the second white board so the reflected light creates a shadow of the business card onto the second white board. Your camera would be off to the side of the reflector board facing in the opposite direction that your flash is facing. Unless I'm missing something, your flash has to be off camera.

I can picture in my head exactly what Nikolai wants us to demonstrate, but I only have one (clean) white board right now and no black posterboard. I'll see if I can buy some boards tomorrow.

I think this exercise is going to be confusing for anyone who hasn't worked with off camera lights before.

TexPhotog

OffTopic wrote:

Almost...reverse the positions of the business card and the second white board so the reflected light creates a shadow of the business card onto the second white board. Your camera would be off to the side of the reflector board facing in the opposite direction that your flash is facing. Unless I'm missing something, your flash has to be off camera.

I can picture in my head exactly what Nikolai wants us to demonstrate, but I only have one (clean) white board right now and no black posterboard. I'll see if I can buy some boards tomorrow.

I think this exercise is going to be confusing for anyone who hasn't worked with off camera lights before.

Ok... 2nd try... something like this then???

Picture9.gif

If I'm catching this now... you'd need to put the flash on a light stand (or a holder/clamp anything) in front of the 1st board... right??? If I don't have a flash extension cord, can I just rorate my flash head 180 deg while keeping it on-camera???

Nikolai

TexPhotog wrote:

Ok... 2nd try... something like this then???
If I'm catching this now... you'd need to put the flash on a light stand (or a holder/clamp anything) in front of the 1st board... right??? If I don't have a flash extension cord, can I just rorate my flash head 90 deg while keeping it on-camera???

Yep, you are definitely on a right track!

davidweaver

Could I see a picture of this rig? I'm having an impossible time figuring this out and I have all the parts hanging around to make it.

Nikolai

davidweaver wrote:

Could I see a picture of this rig? I'm having an impossible time figuring this out and I have all the parts hanging around to make it.

I don't have it And you can do it in whatever way you want. Important thing is to be consistent, scientific and objective.

OffTopic

davidweaver wrote:

Could I see a picture of this rig? I'm having an impossible time figuring this out and I have all the parts hanging around to make it.

Wish you lived closer David - I haven't been able to find black posterboard to save my life. Closest thing I've been able to find is black foamcore at $15 a sheet. Where did you find the black posterboard?

spb13

OffTopic wrote:

Wish you lived closer David - I haven't been able to find black posterboard to save my life. Closest thing I've been able to find is black foamcore at $15 a sheet. Where did you find the black posterboard?

I found it at Joanne's ETC, but I haven't had a chance to put everything together yet.

OffTopic

Thanks Sean. I never thought to check there, always thought of it as just a fabric store. And I have one close by.

davidweaver

I think black foamcore would work. For a deeper black I'd suggest a velvet type of matboard. I would think that Staples or Office Depot had poster board in black. BTW: I paid 9 bucks for a big sheet of black foamcore board at Jerry's art-a-rama.

OffTopic wrote:

Wish you lived closer David - I haven't been able to find black posterboard to save my life. Closest thing I've been able to find is black foamcore at $15 a sheet. Where did you find the black posterboard?