Focal plane distortion

[rjbuzzclick]

http://people.rit.edu/andpph/text-slit-scan.html
About a 'page or so down is a small thumbnail of the right side of a couple dancing. Robert Doisneau, an extra twist...

I tried this myself with a Pacemaker Speed Graphic and this is the best that I got. Check out the position of her feet. I "hand-wound" the shutter slowly using the 1/1000 slit while she was turning on the merry-go-round rather quickly (she was a good sport!). The banding is from the uneven travel speed of the FP shutter slit.:

[John Austin]

it really can't be done with a speed graphic because 1/30 is too fast for that sort of distortion
i have done it ( barely ) with a graflex slr, and a shutter at around 1/15S and a moving bus ( /barely )
but never at a sports event

John,
My SG shutter goes down to 1/10th second - However, I make an assumption that the smallest slit should be set with the slowest tension - (Aperture D with Tension 1 = 1/500th sec) I have found the SG shutter to be fairly accurate

I will take it to town today and try - Results to follow, though I really need a big road, which could we weeks away



Anyway, I feel this is the only one way to find out

[jnanian]

John,
My SG shutter goes down to 1/10th second - However, I make an assumption that the smallest slit should be set with the slowest tension - (Aperture D with Tension 1 = 1/500th sec) I have found the SG shutter to be fairly accurate

I will take it to town today and try - Results to follow, though I really need a big road, which could we weeks away



Anyway, I feel this is the only one way to find out

too cool, you must have a "anniversary" .. i'm short-sighted and forgot
that the older models had like 25 speeds ( i wish mine had 24 of'em ! )
my pacemaker only goes to 1/30 ( only has 6 speeds )

have fun "Jacques Henri"

john

[Sirius Glass]

I have tried it at the slowest shutter speeds on my Graflex Model D, but I still have not been able to reproduce the effect. [rant]Grumble, grumble, grumble [/rant]

[Leigh B]

Hi Sirius,

Your shutter speed is too slow. Go back and read my post #4.

You must use a shutter speed fast enough that the shutter aperture is a moving slit.

- Leigh

[rjbuzzclick]

Correct, you need a thin slit traveling at a slow speed. In my example in post #11, I was trying to reproduce the effect seen in Rober Doisneau's photo of the man and woman twisted around each other. If you look closely at her feet, and follow the line of her legs, you'll see that they're twisted oddly. It's not as great of an effect as I would have liked to get, but it's close. At some point I'll try this again and hopefully have better luck. I was using the 1/1000 slit, but "hand winding" it so it traveled across the film in about two to three seconds.

I ran other tests using the different FP shutter speeds on my Pacemaker SG and was able to get some bending on the upright poles of the merry-go-round with smaller slit openings, but no twisting of my model as in Robert Doisneau's photo.

[Leigh B]

It's funny...

I was shooting sports with a Speed Graphic in the early 1960s and tried very hard to __avoid__ this kind of distortion.

Times change.

- Leigh

[rjbuzzclick]

It's funny...

I was shooting sports with a Speed Graphic in the early 1960s and tried very hard to __avoid__ this kind of distortion.

Times change.

- Leigh

Damn kids these days! Hey, get off my lawn!

[johnielvis]

you'd probably want a long lens too--this will also exaggerate the effect more than a shorter lens since the relative speed will be faster--relative speed is magnification times real speed

[RalphLambrecht]

i thought, yhis image was an example of horizontal shutter distortion with fast-moving subjects, which is different to focal-plane distortion.