Friday, August 12, 2005

Colour Control and Gray Scale Patches

Earlier I wrote about how important it is to keep Photographic Chemistry under tight control. However another impostant aspect to Photographic Control is done in the process of exposing the film. Above is an example of the kodak Colour Control and Gray Scale Patches. These are especially impostant when photographing such things as artworks, fabric swatches and the like.
The Inclusion of these into an image allows a printer to perfectly match a subject via compairing these standardised kodak patches with the image being printed. Because the image has a step wedge ranging from absolute white to black and the primary printing colours if there is any problems with the exposed film, i.e if the image was exposed under colour cast light or is exposed with incorect density, contrast etc... the inclusion of these cards in an image will indicate this to the printer. Other such cards are made by GretagMacbeth.

~ Stephen Frizza

Friday, August 5, 2005

Being In control

A pivotal point that differentiates a Professional Lab from the general 1 hour lab is the degree that processes are controlled from start to finish. There are many things required to keep a close watch on what the chemical processes are doing and these are all kept in line through control strips. The first Image shows 4 control strips for colour processes here at the lighthouse. The first strip is a Fuji Colour negative control strip (c-41) / (cn-15). The second is a Kodak C-41 Control strip which has been run through E-6. Kodak does not provide references for Cross Processing their materials however I do like to keep a check on cross processing jobs by running my own during intervals of the job especially if it is a large job. The Third Strip is a kodak E-6 Strip run through C-41. Once again Kodak does not provide reference strips for cross processing of this nature however I produce my own. The Reason for this is when doing bulk cross processing you must increase your replenishment and its important when making such an adjustment to keep the process in control so that the job is consistent from start to finish. The final strip is a Kodak E-6 control processed through E-6.once these are processed they are measured on a machine called a densitometer which carefully measures the values of the film and those values are graphed according to a reference strip. The Second Image is a Ra-4 colour paper control strip, these are run before printing from colour negatives to ensure that the chemistry which is processing the paper is at its optimum. The third image of 3 Kodak made exposed negatives one is Very Over Exposed, the second is Over Exposed and the third is Normal. kodak releases these for each film type so printers can make correct starting points for filtration and exposure according to their enlargers. These three control methods are the bare minimum pro labs use to ensure they running on line however many other things are done such as measuring the Ph of the chemistry and the specific gravity with tools called Hydrometers etc... These are just a few behind the scenes steps taken at The Lighthouse Lab to ensure chemistry is at its optimum.

~Stephen Frizza