When I got my first DSLR (Rebel T4i), I conducted a few technical shoots to see what noise levels were at various ISO settings. I repeated this with the EOS 6D, but realized I never did so with the EOS 5D IV.
Additionally, since I just moved to new lighting equipment, I wanted to ensure that the camera's displayed histogram matched my gray card and to also determine what Kelvin value best matched my new light.
Regarding gray cards, I have a Datacolor Spyder color checker with colored swatches along with a 50% (18% reflected) gray card. I recently read (perhaps those articles were dated though) that a camera's meter would be closer calibrated to 12% reflected gray. As I'll show belowk for the EOS 5D IV, a 50% gray card shows a spike right in the middle of the histogram. Excellent.
Note: for all images, I had my camera on a tripod.
First up is noise (these are all 100% crops of a color chart). I used a 135mm f/2 lens always at f/16 and 1/200 shutter. I then varied power on my Profoto B10X Plus (from 1.7 when at ISO 32000, all the way to 10.0 when at ISO 100). As the strobe can only be adjusted in 1/10 stop increments, I chose to use a "0.3" value for 1/3 stop and "0.7" value for 2/3 stop. In Lightroom, I adjusted exposure a bit (around 0.05 stops) as needed. Though near the top power levels and lowest ISO values, I did find I needed to adjust around 0.3 stops. I may not have let the light fully recycle perhaps.
Next, I shot my gray card in 100ºK increments from 5000ºK through 7000ºK. For the B10X Plus and 5D IV camera combo, I found that 6000ºK produced the most neutral gray.
Finally, I did the histogram test with the gray card, adjusting my light in 1/10 stop through a range for the distance I had the light at. Then, in Lightroom, I checked which image produced exactly 50% luminance. Which ended up matching my camera's histogram when the spike from the gray card was right in its middle.
Here are various images from the Kelvin and exposure test. Note: For the images where I was at the correct color temperature, using the eyedropper tool in Lightroom to adjust white balance basically did nothing (as expected). Color temp mostly stayed the same, or at most was adjusted by 50º Kelvin. Tint either stayed exactly the same, or increased by 1 unit.
