Can you make a Gray Card - DPChallenge Forums

Canon EF 55-200mm f/4.5-5.6 II USM

02/23/2005 09:59:10 AM · #1

I have been to all the photo shops in my area trying to get hold of an 18% gray card, and most of them havent the foggiest what I am talking about!!
I phoned the Big shop in Munich (Sauters) and they have one for 15 Euro. Seems pretty expensive for a bit of gray card.

So... Is it possible to print one yourself, if so how, & what do you have to watch out for.
How do you test it?

Thanks

Peter

Prof_Fate

02/23/2005 10:04:42 AM · #2

I have a set of Kodak cards coming i got off ebay ($6). b&h has them, i think $15 or so.

I tried to get my laser printer to do it (you can make a 18% gray image/picture in PS or most any editor). YOu should be able to make the 18% gray and have your local photo lab print it out...assuming you end up with 18% gray of course!

For WB I have heard sticking a paper coffee filter of the lens and taking a pic works..i have not tried that one.

orussell

Canon EOS Rebel T6s

02/23/2005 10:13:34 AM · #3

Theorhetically if you set 214 for each of the R,B,G in the colour pallette you get neutral gray. If your printer and monitor are calibrated and you print on paper using the correct profile you should be able to get it pretty close. (Calibrated using Pantone Spyder or similar and using a highend printer.)

//www.graphic-design.com/Photoshop/Tips/getgray.html

Message edited by author 2005-02-23 10:16:20.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

02/23/2005 10:16:22 AM · #4

The problems with printing one out (either at home or a lab are:
1.) If the printed color is off at all (printer calibration and/or profile is inaccurate), you will be setting your camera based on something that is not accurate in tone and/or hue.
2.) A printed card is easily damaged and bound to fade.
3.) A printed card may be a neutral, 18% gray under one light source, but have a color cast under another, different source (metamerism).

The reason you spend a few extra bucks is to minmize these issues.

orussell

Canon EOS Rebel T6s

Canon EF 55-200mm f/4.5-5.6 II USM

02/23/2005 10:20:59 AM · #5

Originally posted by kirbic:

Agreed. But if you need a quick fix or are just experimenting, printing your own could be useful, even if it only means you learned it's not useful at all. If that makes any sense. LOL

scottwilson

Canon EOS-350D Rebel XT

Canon EF 28mm f/2.8

02/23/2005 10:23:49 AM · #6

Originally posted by orussell:

I come up with 117 as the value for r g and b to get and 18% gray, if you are working in sRGB space.

A better way might be to print a number of fine horizontal lines, four black for each white one, this would get to you 20% gray an would not be depended on the color profile.

scottwilson

Canon EOS-350D Rebel XT

Canon EF 28mm f/2.8

02/23/2005 10:25:56 AM · #7

The other thing you can do is metter off of a white piece of paper and then incress the exposure by two stops, this is pretty close.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

02/23/2005 11:03:37 AM · #8

Originally posted by scottwilson:

The other thing you can do is metter off of a white piece of paper and then incress the exposure by two stops, this is pretty close.

There is a potential "gotcha" here as well. If the white paper has UV "brighteners", it may look slightly blue to the camera rather than neutral. It's not likely that this effect would be large, since the UV response of most cameras is probably quite low.

dsb_mac

Best-Buy Easy Point & Click

02/23/2005 11:05:16 AM · #9

I would imagine that if you went to a home paint store you could find a matching grey card for free. Of course you would need an 18% grey already in hand to compare or know which color to get. The good thing is that those cards are matte and printed for a similar purpose as what we do in photography. In addition you could pick up a bunch of other colors to WB off of and get different color casts. If someone could post which paint to get it would be helpful.

Message edited by author 2005-02-23 11:06:25.

Mick

Canon EOS-5D

Canon EF 70-200mm f/2.8L IS USM

02/23/2005 11:08:00 AM · #10

Another thing to consider is the reflectivity of the printed sheet.

Prof_Fate

02/23/2005 11:09:27 AM · #11

A photographer i ran into suggests takin the grey card to the paint store and when you get eth paint, go home and paint you studio that 18% gray.
That is the best suggestion i have had for what color to paint a studio wall yet.

Spork99

OM System OM-1

Canon EF 100mm f/2.8 USM Macro

02/23/2005 11:14:54 AM · #12

I always liked studio walls painted white. They make better reflectors that way.

sabphoto

Samsung Galaxy S8/S8+

02/23/2005 11:26:51 AM · #13

Originally posted by dsb_mac:

Beat me to the response...this is what I do and have about 10 different colored cards that I use sometimes.

Canon EF 55-200mm f/4.5-5.6 II USM

02/23/2005 11:39:54 AM · #14

I am sorry i am a bit confused.. i wondered if any body could explain to me exactly the reasoning for using a gray card now i have heard of it before and know about it when it comes to levels but how could i use when taking pictures or is that not whats its for thanks...
Leon

orussell

Canon EOS Rebel T6s

02/23/2005 11:39:55 AM · #15

Originally posted by scottwilson:

Originally posted by orussell:
Theorhetically if you set 214 for each of the R,B,G in the colour pallette you get neutral gray. If your printer and monitor are calibrated and you print on paper using the correct profile you should be able to get it pretty close. (Calibrated using Pantone Spyder or similar and using a highend printer.)

//www.graphic-design.com/Photoshop/Tips/getgray.html

I come up with 117 as the value for r g and b to get and 18% gray, if you are working in sRGB space.

A better way might be to print a number of fine horizontal lines, four black for each white one, this would get to you 20% gray an would not be depended on the color profile.

I based my assumption on the web page I gave. I have very little knowledge of colour theory (though I'd like to learn - and will). Here's another site with lots of colours in hexadecimal and RBG: //www.pitt.edu/~nisg/cis/web/cgi/rgb.html I must admit 217 looks a little light. I'm going to do some more research.

02/23/2005 12:17:10 PM · #16

Thanks for your replies.

I have an Idea I might try, but let me know If I am heading off in the wrong direction.

Firstly I Print out a Gray card using 214 fro RGB values. (I might use the B&W laser rather than a photo printer as it has no colour to the ink).

Next I take a White Coffee Filter & place it over my Camera to Set the White balance.
I then set up my gray card in the same light Use spot metering or center weighted on it. and photograph it.
WHen I load this photo back into photoshop, it should have a rgb value of 214.
If it is too light or dark, then I can use the Brightness slider to make the original lighter or darker. Repeat this till i get approx 214 for RGB

02/23/2005 12:19:08 PM · #17

Originally posted by LEONJR:

02/23/2005 12:25:03 PM · #18

Sorry Leon.
When a camera measures light to set exposure for a photo, it averages the light read, and adjusts the exposure to produce an image of approximately 18% gray. Therefore if you are photographing in difficult lighting, or need to set exposure before the subject is available, then by using a gray card, your camera can make a pretty good estimate of the correct exposure.
Also If you are going to do a series of photos in the same lighting, E.g. studio shot. Or Portrait shoot (Like I am doing on Saturday of 150 kids), If you photograph the gray card , you can use this in photoshop to help correct colour values, and get rid of any colour hues.

(At least that is how I understand it, never used one yet).

Nikon AF-S DX Zoom-Nikkor 17-55mm f/2.8G IF-ED

02/23/2005 12:40:52 PM · #19

Thanks akiwi, atleast now i actually have a understanding of what 18% gray is but, iam still jus slightly confused, i would take a picture of a gray card? and use that to help me edit pictures? any good website i can get more information on this? thanks in advanced
leon

nicoledb

Nikon D70s

02/23/2005 01:32:40 PM · #20

The way I understood it is that you use a gray card to set exposure, NOT to set white balance. By aiming your camera at a gray card positioned in the same lighting as your subject, you ensure that your exposure settings are correct (that is, correct to produce an object of 18% gray as the middle value in your image). You aim your camera at a white card (or make a picture of it to find out the necessary in-computer corrections) to set the white balance, to correct for blue or orange or other hues caused by your light source(s). The suggestion of the coffee filter works very well to set your white balance, it has nothing to do with setting the correct exposure.

Hope this helps.

Message edited by author 2005-02-23 13:33:40.

dsb_mac

Best-Buy Easy Point & Click

02/23/2005 01:36:58 PM · #21

Originally posted by LEONJR:

You could do it that way. I believe normally you would take a meter reading off the card in the light you are shooting. Thus the camera gives the correct exposure. It's difficult to implement sometimes cuz it's sometimes impossible to place a grey card where your camera is pointing: a landscape for instance.

02/23/2005 01:38:28 PM · #22

Originally posted by aKiwi:

Well I tried it, and it didn't work. Basically it didn't matter if the printed gray card was light or dark, the camera always adjusted the exposure to create a gray that was darker than 18%

Hmmm. Any other suggestions?

goodtempo

Canon EOS-450D Rebel XSi

Canon EF 50mm f/1.8 II

02/23/2005 01:39:57 PM · #23

You can also set the exposure by metering off of your hand because your hand has about the same reflectivity as an 18% gray card. I agree with nicoledb that this method is not for white balance.

02/23/2005 01:44:06 PM · #24

Originally posted by goodtempo:

You can also set the exposure by metering off of your hand because your hand has about the same reflectivity as an 18% gray card. I agree with nicoledb that this method is not for white balance.

I used the coffee filter technique for WB.
As I understand it, you can use the "Set Gray Point" pippette in Levels or curves to help adjust colour balance in photoshop.