Friday, July 23, 2010

Pentax AF360 and AF540 Flash Ratios

Sequence of cross lit photos with incremental
reduction in flash power. In the top row the
right flash is reduced by 1/2 power each image.
Then in the bottom row the left flash is reduced
by 1/2 each image.
I found something interesting enough to drag out the macro set and while I was at it I took some flash ratio photos for a blog post.

I was digging through a box in one of the sheds in the back yard and I came across a clutch of lizard eggs.

While capturing the images I was having some issues with the flash causing shadows that were to strong.

So i decided to bring out my second flash to help subdue the shadows.

This got me to thinking I should take a sequence of both flashes from 1:1 to the flash minimum output.

The camera/flashes were setup like described in Pentax Wireless P-TTL (Part 1).

I set the subject on blue poster board which was curved upwards in the background.

The AF540 was to camera right and the AF360 was to camera left. Both flashes were facing each other but aimed down at about 45 degrees to the subject. The K10D was about perpendicular to the flash axis also aimed down at about 45 degrees.

I started with both flashes at 1/1 and started reducing the 540 (camera right) until it was at minimum output (1/64) then I started reducing the 360 (camera left) down to minimum (1/32).

From the results you can see as the right flash's power is reduced the shadow from that flash is overpowered by the left flash.

Then as the left flash is reduced in power you can see the shadow from the right flash again becoming stronger.

Also you can see the overall exposure going down as the camera settings (1/180@f16) stayed the same through the sequence of photos as the flash power was reduced.

Another thing to note, when reducing flash power you get richer colors. This is also true when shooting through colored gels. If your colors seem too washed out try reducing the power of your flashes. If you are reducing your gelled background light but the colors are not getting richer make sure the spill from any other flashes are not washing it out. Try reducing power or using gobos to block the light.

You can see the full sized images in sequence in my Flash Ratio set on Flickr. Just keep clicking on the right image in the browser to get to the next image.

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