Sensitivity curves in Cyanotypes

[philldresser]

I would like to gain better exposure control in Cyanotypes but dont have a step wedge at the moment. So I want to know if the "Double the exposure equals a one stop increase" rule work in Cyanotypes.

Cheers

Phill

 

[RalphLambrecht]

This the reciprocity law (well almost). But I wonder if you are asking the right question, because you can double the exposure with time and aperture.

Double the exposure (time) equals a one stop increase?
(Yes, unless you have reciprocity failure)
Does doubling the exposure double the density? (No)

 

[philldresser]

Ralph

Thanks for the reply. I was refering to the Cyanotype exposure (UV light) which is a contact print process, so no aperture available. I just wondered if the chemicals responded reciprocally like the Silver processes do, and whether there is a heel /shoulder as well.

Phill

 

[sanking]

Ralph

Thanks for the reply. I was refering to the Cyanotype exposure (UV light) which is a contact print process, so no aperture available. I just wondered if the chemicals responded reciprocally like the Silver processes do, and whether there is a heel /shoulder as well.

Phill

Attached is an image file showing a cyanotype compared to a palladium curve. This curve should give you some idea of what to expect in printing cyanotype, especially as that regards the toe and the shoulder of the curve.

Sandy

 

[RalphLambrecht]

Sandy

Thanks for sharing. What software did you use to do this. Phil Davis'?

 

[sanking]

Sandy

Thanks for sharing. What software did you use to do this. Phil Davis'?

Hi Ralph,

Yes, I used Davis' Winplotter program for the plot. The step wedge prints were made on COT 320 and the densities read with an X-Rite 810. I read the reflection density of the cyanotype with Red channel, and that of the palladium print with Blue channel, which I find gives a better indication of the actual depth of shadow density as seen by the eye than the Visual mode. 100% of Dmax when read this was was about 1.5 for both processes.

Sandy

 

[philldresser]

Thanks Sandy
Thats exactly what I wanted to know.

Phill

PS Are you planning on doing any Alt Process workshops in the UK at all?

 

[sanking]

Thanks Sandy
Thats exactly what I wanted to know.

Phill

PS Are you planning on doing any Alt Process workshops in the UK at all?

No plans for now but I would like to do so, assuming of course that we can get past the language problem. If you know of any organization that organizes and holds workshops of this type I woud appreciate it if you would put me in touch.

Sandy