Gray Background

[ray_parkhurst]

I'm finally back in town, just in time for the DeAnza swap, but it was raining! I checked the website, and it said the swap would happen rain or shine, so I gave it a shot. About 25% of sellers were there, and it was sprinkling, so I went quickly through. I found a nice 2x objective, plus a decent stepped acrylic display rack, and as I was leaving a seller arrived and started unloading. He was descended-upon by 30 hungry buyers (including myself) and we all "helped" with unloading his boxes as we checked out his very eclectic offerings. I left his space with some interesting things:
- A 1.8deg/step stepper motor with exposed shaft on both ends
- A PanaVise head
- A book on Color Theory
- A couple packs of laser sticker sheets

It is these sticker sheets which were the find of the day. They were in the same box as the Color Theory book, and other art and photography items. The interesting thing is they are labeled as "True Gray", which was very intriguing indeed! When I got home, I stuck one to the back surface of one of my Velvet Transfer Disks and snapped a reference pic after doing a quick manual WB. The surface is not uniform one color, but sort of a mottled gray of varying shades. The good thing is the shades maintain the same RGB across the full range of brightness, so they are very easy to WB and are a superb Gray reference and Background.

Here is a 1954-S RPM#4 Lincoln Cent that I've been using as a reference coin for a while, shot on the background. Below the reference photo is the same image with saturation turned to 0, followed by same image with saturation maxed out. I see almost zero color shift in the background as I change saturation! This is a hard quality to come by in a background.

Image was shot with a 75mm Nikon EL-Nikkor at f5.6 and two diffused Jansjos:

Here are the images:

[Maineman750]

That's amazing, Ray...I can barely detect a color shift and probably would not have if you hadn't mentioned it....I'll have to experiment with gray now

[onecent1909]

Nice addition
I always have a hard time with my White balance
I may have to look for something like that

Is there a name or identifying marks with them?

[ray_parkhurst]

That's amazing, Ray...I can barely detect a color shift and probably would not have if you hadn't mentioned it....I'll have to experiment with gray now

One thing that the gray background can give you is a reference that can help to give the correct brightness to a coin. The process is:
- Adjust manual white balance with the gray background
- Shoot the background with EV=0
- Check the shot to make sure the RGB values are equal (within 3-5 points)
- Adjust the WB as necessary using the WB shift function in EOS Utility
- Place the coin on the gray surface, focus, and shoot
- Open the shot in DPP, and adjust levels so the background has the same levels as the reference shot without coin

This will give you a "calibrated" exposure level, with the correct relative brightness to the coin.

[jfines69]

That is cool... From 0 to max saturation with little to no background color shift... What did you set the WB at for 0 and max saturation???

[ray_parkhurst]

I kept the WB the same for all, just adjusted saturation level in Digital Photo Professional.

[jfines69]

I kept the WB the same for all, just adjusted saturation level in Digital Photo Professional.

Thanks for the follow up Ray!!!