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| This is my test scene. A variety of colors on a sunny summer day. More information is in the narrative. (click to enlarge) |
The genesis of this limited comparison experiment is that I really like almost everything about the Nikon Z7 except the color of the blue skies. Way too much magenta in the blue for my liking. I've been manually changing the hue in the images I make with that camera. I thought I would shoot a Fujifilm Astia film simulation (which I find has pleasing blue skies to my eyes), determine the differences in the RGB values of the two renditions of the blue sky, then construct a preset so in the future I can easily change the blue skies in the Nikon files to match the blue skies in Fujifilm Astia files. Easy enough.
Not being able to leave well enough alone, as I was logically thinking my way through the setup and process of how to create files that are basically equal in luminance, it came to mind that this would be a good opportunity to test a) if the old Sunny 16 rule we used film applied to my digital cameras, b) what differences I find in the ISOs of my cameras in creating identically exposed images and c) how different are the in-camera Sunshine white balance settings from Lightroom's WB tool and how different are they from each other?
For those of you who may not be aware of the Sunny 16 Rule, it goes like this. On a sunny day, between 10 a.m. and 2 p.m., with your back to the sun, a proper exposure is 1/ISO @ f/16 (or equivalent combinations). Here is an example using ISO 200, which is a common base ISO on many digital cameras. With the sun at your back a proper exposure should be 1/200 @ f/16. A more useful combination may be 1/1600th sec. @ f/5.6. This is how film exposure was standardized. But does this apply to today's digital cameras? I kind of have an idea but don't rightly know so I'm testing this on my four cameras.
The other question that arose is, "Do identical exposure across my four cameras produce identical files?" For example, in manual mode, does an exposure of 1/100th sec @ f/5.6 at the same ISO and all other things being equal look the same on all of my cameras? If they do, then the ISOs are pretty much equivalent. If not, then manufacturers may be using different standards when calibrating their cameras.
To conduct these experiments, there are all kinds of ramifications to consider to ensure that all things are equal and no editing process changes things. For example, I decided I needed to expose my images using the JPEG file format as all settings, i.e., white balance, ISO, contrast, saturation, sharpness are baked into the file in-camera. If I shot RAW files, then Adobe Lightroom's engineer's rendering of the files may change the way they appear. You've seen this when you've viewed a RAW file next to a JPEG in Lightroom. They can look very different. In fact, I find Lightroom often times reads exposures as 1 stop underexposed when a simultaneously made JPEG shows proper exposure.
To measure white balance, it has to be set on Sunny, not Auto WB to remove any differences in the AWB algorithms. ISO has to be specifically set, manual mode invoked so you can precisely control the exposures (same aperture/same shutter speed), no exposure compensation engaged, film simulations and/or camera profiles/styles need to be set at a "Standard" or "Natural" or other normally rendered setting so each file from each camera doesn't have a high contrast (think Velvia), portrait, landscape or other specialized profile applied. All controls for in-camera contrast, saturation, color, etc., need to be zeroed out. The idea is to have all things as equal as possible across the four cameras.
I went out on a day with no clouds at around 11 a.m. to conduct this experiment. I set up each camera identically, everything the same for each camera, shot one set of images with each camera using an X-Rite Colorchecker Passport in the frame so as to be able to evaluate proper exposure, white balance, the hues of all of the colors. I then shot another set of images of the exact same scene without the Colorchecker in the frame.
I've now made the exposures, imported them into Lightroom Classic CC and am currently working my way through them to determine what differences I'm finding. Come back Wednesday for the first of the results.
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Thanks for looking. Enjoy!
Dennis A. Mook
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Dennis, have you found value in the X-Rite Colorchecker Passport? I would like to be able to spend less time sitting in front of a computer processing images, and am wondering if that would be a path to accomplishing that.
ReplyDeleteJim, yes I have. The system will allow you to create a profile for each camera and under each lighting situation, if you need to. I create one for sunny days for each of my cameras. If I were still photographing professionally, I would create more profiles but I don't need to. The sunny day one works fine.
DeleteThe software X-Rite provides works as a Lightroom plug-in and shows up in the export dialog box to create the profiles. Briefly, you take a RAW photo with the Colorchecker in it and then import that photo into LR. You export the image using the X-Rite selection in the export dialog panel, name the profile and it creates the profile. Very easy. After creating a profile for a camera it shows up in the Develop Module as you would find other camera profiles that LR already provides for your camera.
I use it to match colors if I'm using two camera brands for a single event. I also use it for white balance and exposure calculation. I keep the Colorchecker Passport in my camera bag and if the situation has funky light, I pull it out, take a photo of it in the same light, then I can color correct all of the images I've made under that light at one time.
Hope this helps.