Using Grey cards in digital photography
Before we start I think it is important that you understand that I have a love hate relationship with grey cards. This in and out of favour relationship has been going on for a fair number of years now and I can see no end in site. So I state for the record, if you choose to start using grey cards after reading this blog I will in no way be held responsible for your mental health.
Right, that’s out of the way. The beginning of the relationship; I first started using Kodak 18% Grey cards when I was at collage. We were taught how to use grey cards to get accurate meter readings and how useful they were when producing colour prints, for getting accurate colours. Or at least that was the theory. Nine out of ten times we forget to take a shot with the card in it or when we did remember the grey card shot was the only usable one from the whole shoot.
My next encounter with the grey card was when taking pictures of the interiors of very large agriculture buildings. If you have livestock in the building flash is not an option. To get a picture you have to use the available light. This consists of what daylight is available. You then turn on every artificial light you can find. These are normally a 25 watt light bulb covered in the grime of ages, 40 feet above the floor. Then the last element is your portable photographic light. The resultant negative has so many different colour temperature light sources that they are almost impossible to print with a grey card as reference.
Having left the difficult interiors behind next came product shots. By carefully placing a grey card in a product shot you can get a very accurate meter reading. The draw back is when the grey card falls over and destroys the few last hours work. We all breathed a collective large sigh of relief when Polaroid backs became affordable. A quick Polaroid, look at the result. Adjust the exposure, deal with the odd stray highlight or two, change the backs, take the picture and move on to the next one. Grey cards had been banished to the back of the draw forever.
When we started taking wildlife pictures I never dreamed that grey cards could ever come back into my life. After all, never mind knocking things over. Who could you persuade to place a grey card on a sleeping Lions head? Although, come to think of it perhaps Elephants are natures answer to grey cards.
Lulled into a false sense of security, I was processing pictures of flowers. Particularly please with my efforts and in order to show off, I proudly announced to Jacky to come and look at the beautiful pictures. She quickly pointed out that it could be greatly improved if the flower, instead of having a distinct bluish tinge, should be yellow.
After some thought, it seemed to me that we needed some sort of colour reference when taking certain photographs. The only problem with grey cards and the great outdoors is that most grey cards are made of card and not designed for the rough and tumble of wet grass muddy fingers and the occasional woops that’s were I left it.
Enter the X-Rite ColorChecker Passport this small bit of plastic has almost banished the hate side of my relationship with grey cards. Small, portable and with protective plastic; it is grey card that fits into your pocket and does not come out bent and dog eared.
What X-Rite, makers of all things to do with colour have come up with is a fit in your pocket colour chart. The Passport has three leaves just like a book. Each leaf containing a different set of colour targets for different tasks. You have the "Creative Enhancement Target" (CET) what a mouthful. A "White Balance Target" (WBT) and a "Classic Target" (CT)
The CET contains set of patches that go from black to white along one edge. These patches allow you to adjust the exposure until the highlight or white patch has just stopped clipping. Next are a set of colour tinted patches. Using these you can adjust the colour balance in a controlled way. For instance, in Adobe Lightroom, by clicking on one of these patches would give you much the same result as if you had used a warming or cooling filter in the days of film. Lastly you have a set of colour patches these give you a visual reference for colour adjustments such as HSL (Hue, Saturation, Lightness)
If you use a JPEG workflow then the WBT is a must for you. It provides you with an easy to carry bit of white card. Instead of using all manner of unsuitable whites such as shirts, hankies, walls and even the odd wedding gown; you use the passports WBT to get a proper 80% white to balance the JEPG output against.
Last but by no means least is the CT or as it is better known to many the GretagMacbeth patches. This set of patches has been around for as long as I have been taking pictures. Providing a set of standard colours you can do many wonderful things, more of which later.
To use the X-Rite ColorChecker Passport select which set of patches you are going to use. For us this is normally the CET and the CT patches. Place the passport in the picture or in the same light and take a picture. The only thing you need to worry about is getting the exposure correct. So check the camera’s histogram and highlight warning if it has it. Check that the white patch on the exposure section is recording some detail.
Opens like a book to make a stand
Passports are designed so that moving the leaves of the book to different angles; you can make it stand up in almost any situation, well almost. We haven’t tested its stand up capabilities on sleeping Lions yet! As soon as I find a willing volunteer I will of course be reporting back. When you have finished, close the Passport and the patches are safe from all the normal fates. Slip into a pocket or camera bag ready for next time.
Great with yellow flowers
Back at the computer download your images into your favourite software. Currently, ours is Adobe Lightroom. Find the image of the Passport and click on one of the grey patches with the eye dropper in the Develop module. All being well you should have a perfect colour balance for that picture. Next, find and highlight all the other pictures taken under the same lighting conditions. Synchronise the images using the colour balance settings and all your pictures will have perfect colour balance. It is as simple as that.
Now if that was all there was to the X-Rite ColorChecker Passport it would be worth its money. Being able to colour correct images quickly and accurately is good news. But the Passport has another trick up its sleeve.
Enter the X-Rite ColorChecker Passport Camera Calibration Application software. What does it do? For instance, take a picture of the Classic Target in daylight. Then import this image into the Camera Calibration Application and it will produce you a DNG profile.
Now for the really complicated bit; Digital Negative Graphics (DNG) is in fact an open file format created by Adobe. You may have come across its open standards format for storing your own digital files. We have been using it as an archive file storage format for a number of years now. The good thing about this file format for colour work is that it can contain camera calibration information within it. Because these DNG files can hold camera calibration information you can use this calibration information in software like Adobe Photoshop and Lightroom.
If you are now as lost as I was when I first read about DNG profiles and DNG files, I fully understand your plight. Maybe this will help?
Take a picture of your X-Rite Passport using RAW. Convert this RAW file to DNG. Import this into the ColorChecker software and it will produce a camera profile for you. This camera profile is exported as a DNG file from ColorChecker. This profile DNG file can be used by programs such as Adobe Photoshop and Lightroom when developing your images in ACR (Adobe Camera Raw)
Is having your camera calibrated a good thing. If you own more than one camera body it is a great thing. Normal camera calibration files are specific to the camera model but not to your particular camera. In the days of film Kodak and Fuji spent untold millions on making sure that their film produced the same colours year in year out. With digital cameras this consistency has been lost. No matter which make of camera you use, the chip inside has a wider manufacturing tolerance than film ever did. Shoot a picture on identical model cameras can produce very different results.
Adobe Lightroom and ACR use a generic profile for each camera stored in a file called Adobe Standard. These generic profiles correct most of the differences between camera makes and models. The aim of this profile is to bring all imported images to a common look. Being all things to all makes of camera is a great ambition and Adobe have in there usual fashion done a great out of the packaging job. The standard Adobe profiles are a vast improvement on what went before. But as always there is room for improvement and this is were ColorChecker Passport comes to your rescue.
Producing an exact profile for your camera body gives you several advantages. You get better more saturated colours and normally a first imported result that is closer to the original scene than if you use the generic Adobe Standard profile. X-Rite ColorChecker software when you install it provides add-ins for both Adobe Photoshop and Lightroom this makes it very easy to produce a camera profile.
As I have said before the X-Rite ColorChecker passport has almost won me over to the whole grey card world. It is now possible that I regret not taking a grey card shot when I return with pictures. It has also improved the quality of our pictures. It has reduced time spent fiddling with sliders, wondering if my colour memory has failed me or that flower should be blue. It is not long live the grey card yet but it certainly is long live the ColorChecker.
Until next time.