If you have ever made a print, either by inkjet or an alternative process (like Van Dyke, Platinum, Cyanotype) then you may have noticed that the image comes out a little bit darker than how it was displayed on the screen. Looking into this, the main reason (especially for inkjet) is that screen is back lit and the print isn’t, therefore the perceived level of luminosity is different. For an alternative process (i.e Chemistry based), this is likely to be the same, also, the print can become darker due to the drying down process (even after calibration of the negative to the chemistry).
The main driver for this post is to document a dry down issue with an alternative printing process with chemistry. For this purpose, the Lightroom way of controlling the output isn’t precise enough, there for Photoshop CC is the only way to control the output. I thought i’d write a post on different ways in both Lightroom and Photoshop CC to solve this problem and then to correct the image before the print is made.
Printing from Lightroom is super simple and works really well for Inkjet prints. When printing from Lightroom within the Print module, there is a slider that can be changed before you print, called Brightness. This will adjust the brightness of the print to counteract the reduction of perceived brightness in the print. This is great and highly useful, but i’d advise you to make a few prints first to understand how it will affect the physical output.
Photoshop has much more control over this phenomenon and suits specific types of printing, including inkjet printing and alternative processes.
In Photoshop CC there are three effects/controls that can be used to manage the output, Exposure, Brightness and Gamma.
Exposure is one that i’ll touch on first, as this is the one that is most synonymous with Photography. It would make sense that exposure would be a way to control the amount of light within an image, as this is the way that a camera works and ‘exposes’ the final image. Adding 0.3 of a stop to the exposure value on this step wedge (i’ know it’s not very exciting, but it does show the new distribution of values across the gray scale).
It turns out that when the Exposure modification is mapped to a curve, we can see what it’s actually doing to the image. Exposure seems to affect the highlight values much more than shadow values. To apply Exposure it is available from the Photoshop toolbar menu, under Layer / New Adjustment Layer / Exposure.
Brightness is another way to altering the relative values of the output. Brightness is available from the Photoshop menu under Layer / New Adjustment Layer / Brightness and Contrast.
What brightness actually does to the values is
The brightness control actually increases the highlights gradually, then tails off through the midtones and hardly affects the shadows.
The gamma control is available under the levels adjustment layer, and can be found under Layer / New Adjustment Layer / Levels. In the example below, a value of 0.10 has been added to make the image lighter.
The Gamma actually controls the gradual equal lift of both highlights and shadows as well as increasing the mid tone values.
Based on this, i’d recommend looking into the Brightness or Gamma for the control of the dry down/dark prints, these seem to have much more control of the shadows and highlight areas and won’t make a big difference to the contrast of the desired image.