Our 6th meeting of the new season was a member driven night aimed at sharing tips and techniques that might help all members of the club improve their photography in one way or another. The focus this week was on achieving better output in terms of image quality, and in particular colour images, whether the image would be shared as a digital image, or as a print.
Color Checker Passport
To begin with Lionel demonstrated how he achieves correct colour using the X-rite Color Checker Passport. There are a few variables in how colours in our images are recorded by our cameras. To start with there are differences in the characteristics of the light in different regions around the world. Then the light is effected in different ways as it enters our cameras through each different lens we use, and finally our camera sensors and image processors record the information in slightly different ways. All of these lead to inconsistencies in how colours are recorded in the final image file. The aim of the Color Checker Passport and similar products by other manufacturers is to achieve true colour by recording a series of standard colour swatches and using software in post capture to reference these swatches and create a colour profile specific to all of the variable factors relevant at the time of image capture.
Screen and Printer Calibration
Display monitors and laptop screens are not perfect and they certainly are not all the same when it comes to how colours are displayed. Obviously this can lead to problems when it comes to producing prints or even preparing images for use on other devices such as the club or a NIPA projector.
BPIC has two ColorMunki devices, available to members for display screen and printer calibration. Screen calibration is aimed at ensuring a standard set of colours across all calibrated devices. Michael demonstrated the use of these devices for screen calibration and talked about how this is taken through to printer calibration.
Producing a Test Print
Even after screen and printer calibration, getting the correct ‘exposure’ or level of lightness in your print can be difficult. Prints can often look darker than the image on your monitor. This is because the monitor that you use to edit your image projects light, but the print reflects it. Michael demonstrated a method used to produce test strips in Photoshop aimed at achieving the perfect exposure in the end print.
Create a Printing Test Strip in Photoshop
A test strip divides your image into seversl sections each with an incremental amount of exposure.
1. Open your Image in Photshop.
2. Add Guide Lines. Let’s say we want from +1.5ev to -1.5ev. That is 7 sections we need to split our image into 7 even strips. Go to View then to New Guide Layout, which will bring up a dialogue box that allows you to tell Photoshop how many guides you want. Remember to keep the gutter at 0.
3. Create Exposure Adjustment Layers. With the rectangular marquee tool, select the first strip on the left of your image. Next, click the new adjustment layer button at the bottom of the layers palette and navigate to Exposure. Here you will insert a value of -1.5 into the exposure field box. Repeat this step for all 7 strips creating new separate exposure adjustment layers for each strip you select with the rectangular marquee tool. Use the values of -1.5, -1, -0.5, 0, +0.5, +1, and +1.5 as you move from left to right.
4. Add Labels. Now you have a banded image on the screen it is good practice to add labels to each strip.
5. Print Test Strip. You can now print the test strip and use it to work out how much exposure compensation should be applied. At this stage you can save the file as a .psd file so the various layers stay intact. It also means you can change the image and use again.
A similar approach can also be used to make adjustments for colour related issues you may be having with your prints. If you are getting unusual colour casts or incorrect amounts of saturation, then try the steps detailed above but instead of using exposure adjustment layers, use Colour Balance, or Hue/Saturation.
See the full article here.