Friday, March 12, 2010

Testing ED's Flash Guide Number

Now the test pictures. For the set-up see here.
All pictures are taken with ISO 400 and the camera set in manual mode.
1/30s Aperture f2.8 flash
In all pictures with 1/30s only the flash contributes to the exposure. At f2.8 "Snoopy" is overexposed and the garden wall looks about right.

1/30s Aperture f4 flash
"It's OK! Leave it! Good Boy!"
Wolfi looks about right, Snoopy is a bit to bright because he is white. That is near the right Aperture.

1/30s Aperture f5.6 flash
Now at f5.6 Snoopy is about right, but you see a strong fall off of light behind him. The Garden wall is now quite underexposed.
Guide number check: ISO 400 gives a double factor to the guide number compared to ISO 100. The calculation is distance 4m x Aperture f5.6 / 2 for the ISO and results in Guide number 11.2. It is rated 14 which is close enough and after all ED has already 33 years working life behind him.

1/30s Aperture f8 flash
With 8 Snoopy is clearly underexposed. You can also see that the garden is very dark. looking through the viewfinder I could basically see nothing. Auto Focus does also not work.
David recommended in his Seminar to use a torch light for situations like this. It is critical to keep the Auto Focus in manual at the lens and at the Camera. Otherwise the AF starts hunting when you want to take your flash picture.
I wanted to make a couple of picture with the torch light placed on the floor, ("Wolfi! Noooooo!") to get a mix between an ambient light and flash and to show the relation between time and aperture. First I tried a couple of shots without flash.

4s Aperture f4 no flash
The torch lights Snoopy OK, but the garden is black.

8s Aperture f4 no flash
Garden still black, Snoopy a bit overexposed.

15s Aperture f4 no flash
Snoopy nuked, lawn very dark, the wall and plants in the back show up.

15s Aperture f4 flash
So now I bring the flash back on. With Aperture f4 the garden is really bright, however Snoopy is still nuked by torch and flash.
The shadow of Snoopy is nice and could be a bit more emphasised by reducing the overall background brightness.

8s Aperture f4 flash
I bring the time down one stop so that the torch light is reduced. Still way too bright.

8s Aperture f5.6 flash
I also want to reduce the flash. Therefore I need to close the aperture one more stop. Aperture cuts ALL light that contributes to exposure. Remember: Time cuts ambient light, Aperture cuts flash and ambient.

The shadow becomes more visible. But Snoopy is still a bit too bright.

8s Aperture f8 flash
One more Aperture down. Now the middle ground is quite dark. The shadow stands out and Snoopy is kind of OK, if not a bit on the bright side.

15s Aperture f8 flash
Bringing the time up one stop again brings some detail into the middle ground, but Snoopy is much too bright again.

30s Aperture 8 flash
"Enough attention for Snoopy! That is MY toy!"

You might ask so what's the point? After all we could not find a satisfactory lighting with the torch and the flash. I wanted to illustrate a few points by the strobe experiments ( i have to keep repeating the title from time to time).
1) We tested the guide number of ED. It seems to be between 11 and 12 rather than 14. Good to know for me. You also know now how to test for the guide number of your flash. It would have been much better to use a grey card leaned against snoopy for a more exact result.
2) By varying aperture and time you can see how such changes influence the picture result. Aperture is the only way to regulated a manual flash. BUT it also changes the ambient light level at the same time. The time setting only changes ambient light.
3) It is really desirable to be able to vary the power of your light sources. A flash with only full power and a torchlight with only one power setting are both less than ideal. Basically they stink! Even with a stationary setting. Theoretically you could "regulate" both by moving them closer or further away. Such an approach has practical limits in the space that is behind you when you move it away and the fact that you do not want either in the picture when you move them nearer.
4) In this set-up I wanted to also show the light fall off. I placed ED deliberately low so that the grass shows nicely the different light levels. A typical (bad) flash picture is normally quite overexposed in the foreground bright in the middle and pitch dark in the background.
So what's next? We want an automatic, we want to be able to vary our light sources. Before that one last session with ED. Above we see the shortcomings of flash when lighting an extended space. So what about a flat object? A large flat object should be lighted perfect at the right aperture?
Also never trust only one experiment you might have got something wrong without noticing.
Stay tuned for the last appearance of ED (in a leading role) in the up coming "ED and the garage door".

Wednesday, March 10, 2010

Time and Aperture with Manual Flash Set Up

I want to use a small old Canon flash, called ED, to experiment with time and aperture. I am too lazy to use a film Camera and it is NOT save to attach ED to my digital camera.
I came up with this set-up. Camera on Tripod in manual mode. Attached by remote cord is a SB-900 set to manual, 1/128 power and 200mm zoom. Having the SB-900 dialed down as much as possible and pointing away from the scene should ensure that it has no effect on the picture taken.
Another word of advice: Did you ever wonder why Pro photographers seem to be fascinated with the color black in their fashion choice? Remeber the GPP shootout? All three photographers  and all assistants wore black T-shirts.
Well, on this occasion I also wore a black t-shirt because I do not want to act as an unwanted reflector. Which might have had an influence in this set-up when the trigger flash points towards me.

ED is attached to the Chinese DP1 photocell. The SB-900 in manual mode does not emit any pre-flash, so I could have taken any photocell. I used the DP-1 to run a mini test. (No pictures)
When I set the SB-900 to manual and the DP1 to expect a pre-flash, it does not fire when I take one picture. When I take two in quick succession it does fire. When I set the DP1 to normal operation it fires reliably. No pre-flash in manual mode! This is the kind of useful information which is either not in the manual or buried somewhere so it always handy to run the tests.

Another little side remark: I took the picture of the set-up with a fairly recent point and shoot the Canon Power Shoot A2100. You can see in the first picture above that I forgot to switch off ED so it fired and nuked the SB-900 and the plant. When taking the picture from the front I thought to keep it on and make a number of pictures in succession. I thought that the recycle times of my 2009 Digi-Knips would surely be faster than ED from the year 1975. (He is older than most participants in Davids GPP workshop.) So I hoped to get one picture with ED firing and the next one without. Man was I wrong! ED kept up the recycle times right with the Powershot all pictures had ED firing. I had to switch it off to make the shot above. Way to go ED!!! (If you look at my reflection in the glass door you see that I really wore a black t-shirt.)

I used a stuffed Toy of my dog Wolfi as a model and placed it exactly 4 m away from the flash into the lawn.

Now the set-up is complete and I am ready to go.

At least that's what I thought!
Wolfi thought: "Oi! That is MY toy!"
I could convince him to lend me the toy for a good cause in the end and I will post the example pictures tomorrow.

Tuesday, March 9, 2010

GPP in Dubai

I attended the last Day of GPP last Saturday in Dubai and had a really good time. It is highly recommended.

In the morning I attended David Hobby's Workshop "Lighting in Layers". David's method of "layering" and keeping control of his lights by manual settings was really interesting. He also shared a good number of Tips (ranging from lighting to life coaching) and was great in answering the many questions. Thanks a lot David!

In the picture above he sets up a "Band" shot with the main light comming from an SB 800 and using an IKEA lamp shade as light modifier.

In the evening the event ended with a show in the auditorium and the highlight of the show was the shoot/out between David Hobby, Zack Arias and young Joey L.

See Davids Blog here and Zacks blog here. Please have a look at their blogs. I am not repeating the details. The photo below is the making of for Zac's final picture.

Young Joey L kept true with his "cool kid on the block" image and delivered a Polaroid which he taped to the screen so that the audience could see the two minute post processing.

One thing that struck me in Davids Workshop is that there are at least two generations out there who never saw a manual flash. The super-duper CLS iTTL Auto BLS Fillflash actually blurs what is going on. So I will continue with the examples right from the basics.

I have thought out a set up to continue wit the small Canon flash in manual mode which will be comming up soon. Stay tuned.