Photography-fi: DIY Grey Card for poor people (20 cents)

[kin0kin]

I made an 18% grey card using photoshop, setting the color to 18% CMYK, filled a 4X6" frame and had it developed using kodak royal paper - matt. It was actually developed from Walmart.

This is what 18% gray should show on histogram - middle ground:

Here's what I got from the DIY card:

and here's how I measured it:

Yes the picture is slightly crooked, and it does affect the reflection a little but there's no significant difference! My camera meter was jumping around 1/3 shutter speed, so you do get 1/3 stop accuracy with the card depending on how crooked it is . All for 20 cents, perfect for poor people like me.

For n00bs:
[size=xx-large]How to use it[/size]
1) Download the attatchment. It is a 4 X 6 Image, you can enlarge it to whatever size you want (quality doesn't matter, it's a flat color)

2) Send the picture to be developed by any shop. Have it developed on a matt paper.

3) Set your camera to spot metering.

4) Place the card beside your subject, aim your camera and meter the card, lock the EV, compose, and shoot.

5) You can also set WB using the 18% grey, or flip the picture over to set the WB to white.

enjoy

 

[Davesrose]

Only thing is you should be sure whatever printer you're using should be calibrated to whatever color space your graphics is set to. If you want to be anal about 18%....some photographers like to argue that 18% isn't all that. I usually just spot meter my middle tones if I'm getting really anal about metering.

http://www.bythom.com/graycards.htm

Just as an anecdote, but it's also hard to reach an agreement about what middle gray is too....if you plug in 50% Luminance in Photoshop, it will only be 46% B in the HSB scale, 119 in RGB, and a whole mix in CMYK. And some say that 116 RGB is true gray. And that's just the 8 bit scale....what if we go 12 bit or higher

 

[kin0kin]

The thing is try not to print them yourself with your printer unless, yes, it is calibrated, and you've gotta make sure your proof the colors. The best way is to just have it developed outside and you need not worry about getting incorrect color.

Regardless, the color is mainly to reduce the light reflection, it is the measured light reflection that matters, not the color. Which is why I printed it on matt paper. You might get slightly different result if the card was developed on a glossy paper. It's only a few cents to try, there's just no harm trying.

 

[Davesrose]

Quote:

Originally Posted by kin0kin /img/forum/go_quote.gif The best way is to just have it developed outside and you need not worry about getting incorrect color. Regardless, the color is mainly to reduce the light reflection, it is the measured light reflection that matters, not the color.

That's the thing though....you don't know how accurate a developer is. Even with film development....if you took it to several developers, they'd all give you slightly different colors because of their differences in equipment and developing solution. That would be especially true of the 1 hour photo places (you never knew how fresh their developer was, or if the machine was operating well or whatever).

With metering, it's not the hue that matters as much as the value. You have to be sure the color is the right value in order the get the right amount of light reflected (though of course each color channel has its particular chroma that would change the value of light too....but we won't get into that). However, many digital photographers like to make sure the gray is as neutral as possible, so that they can use it for custom WB as well.

When I've read photography forums, it also seems that there's been a debate about how matt or glossy the paper should be for a gray card. I would think that as long as it's not glossy enough to reflect back stray light, it would give more color contrast. Although the bigger factor would be the type of ink used in the printer. Particular pigments have their own reflective properties as well....

So, in short, it's actually a very complicated thing because computers and printers can never be 100% calibrated towards one another.

I looked up what Walmart uses....aparently, they use a Fuji Frontier printer. Here's a link for all those interested in using Walmart: using one of these profiles might give you the best color:

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=006w4ahttp://www.drycreekphoto.com/icc/usi...r_profiles.htm

Actually, in another thread someone brought up a good idea IMO. That you can get your local hardware store to mix up 50% enamel or latex paint. Since their computers are mixing the paint specifically for the type of paint, you know that it will stay that color. Then the trick is to paint it on smoothly on some foam core or cardboard:

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00CAi4

But ultimately, getting correct exposure is more of a guess then a pure science....the art of photography is making your own interpretation that seems more "natural" or "pleasing" to the eye. Use whatever floats your boat to try to figure out how to expose those midtones

 

[AlanY]

Quote:

Originally Posted by Davesrose /img/forum/go_quote.gif That's the thing though....you don't know how accurate a developer is. Even with film development....if you took it to several developers, they'd all give you slightly different colors because of their differences in equipment and developing solution. That would be especially true of the 1 hour photo places (you never knew how fresh their developer was, or if the machine was operating well or whatever).

This is true. Also, most commercial digital photo printers automatically "enhance" the colors and brightness to compensate for most people's uncalibrated displays. Some places, like Printroom.com, give you the option of choosing whether to do this, which is nice, and they may supply an ICC profile of their output device for matching. If I was printing a DIY grey card, I'd probably go with a printer who can do real black and white silver hallide prints. (Again, Printroom.com is one example, but there are others.) That ensures you get a true grey.

 

[mbriant]

I forget where I read it, but somewhere it said that the 18% grey was incorrect ... that it should actually be 12% or something like that. I do remember thinking "this is odd" because wherever I read it seemed like a very credible source.

EDIT: Here it is: http://www.bythom.com/graycards.htm

google can be amazing some times.

 

[Davesrose]

Quote:

Originally Posted by mbriant /img/forum/go_quote.gif I forget where I read it, but somewhere it said that the 18% grey was incorrect ... that it should actually be 12% or something like that. I do remember thinking "this is odd" because wherever I read it seemed like a very credible source.

Yeah, I linked to that up above. I suspect that true gray is a little lighter then 18% reflectance. When I typed in 50% luminance in Photoshop, I got RGB values of 119....slightly higher then what some recommend for printing a gray card (116). Splitting hairs anyway!!

 

[kin0kin]

Actually I think people are getting too "serious" about the developer's end. It is really simple:

1) Picture #1 shows the correct exposure you should get for 18% grey on a histogram

2) Picture #2 shows the exposure measured with the 18% grey card and the historgram shows a similar exposure as an 18% should be

3) Grey card is accurate.

so, go develop some cards, and start measuring, and you will know if the developer did something to skew the color, or the color is faithful and how it should be. My local Walmart did a great job.

 

[dj_mocok]

Up to this day, I still never adjust my camera using grey card. Any significant difference?

 

[GAD]

Quote:

Originally Posted by Davesrose /img/forum/go_quote.gif But ultimately, getting correct exposure is more of a guess then a pure science....the art of photography is making your own interpretation that seems more "natural" or "pleasing" to the eye. Use whatever floats your boat to try to figure out how to expose those midtones

X2!

GAD

 

[Davesrose]

Quote:

Originally Posted by dj_mocok /img/forum/go_quote.gif Up to this day, I still never adjust my camera using grey card. Any significant difference?

Depends on you

You may find it easier to find your mid grey by just metering by card. I find I get better results by spot metering several mid tones and coming up with my own average. That's if I'm really anal. Otherwise, center weighted, partial, or evaluative when needed

Quote:

Originally Posted by kin0kin /img/forum/go_quote.gif 1) Picture #1 shows the correct exposure you should get for 18% grey on a histogram 2) Picture #2 shows the exposure measured with the 18% grey card and the historgram shows a similar exposure as an 18% should be 3) Grey card is accurate.

Since you're going by rough histograms, accurate is relative

If I were trying to get absolute gray on the computer, I would make sure it's 50% luminance in CMYK under Photoshop (the monitor is never going to give you the exact same gray). Once you expose, if its not dead on the center, you know the printer is that far off. But it's still not a precise science as your camera's histogram would be slightly different then Photoshop's. Anways, just some thoughts from one of the "serious" guys

 

[kin0kin]

Quote:

Originally Posted by dj_mocok /img/forum/go_quote.gif Up to this day, I still never adjust my camera using grey card. Any significant difference?

The thing about using a grey card is that it allows your camera to meter the exact 18% grey so that pictures are all exposed in the right "zone". Basically you'd place the card beside your subject and spot meter the card, then do your thing - compose, shoot. This would give you a proper exposure of the subject.

On the other hand, if you use matrix metering to meter your subject, which say happens to be in a scene where there's a dramatic difference in contrast...i.e. black shirt, brown skin, very bright sky. The matrix metering will take all the exposure and average it to give you an 18% grey. It's basic math here, when you add an extreme value to the sample, the median will get skewed. Therefore, in such scenes, you'd often find your subject slightly under/over exposed.

However, if you want the brown skin tone to be properly exposed, you place the grey card beside the subject you want properly exposed, meter the card, and viola, your subject would now be properly exposed, but because the camera cannot capture the whole dynamic range, some of the extreme value will now be clipped.

 

[dj_mocok]

So do you guys actually find any difference between between the "before and after" adjusting to grey card?

I mainly shoot manual, and so far even if I use my auto lenses, the overall result is still satisfying. Plus for pictures that I like, I usually post process them and that for the most part includes adjusting brightness/contrast/and whatnot...

That's why I never really bothered with it... unless there's a huge difference and I should really adjust my camera?

 

[Davesrose]

Actually, if you shoot in RAW, you can adjust exposure a few stops in PP. That gives you more control then having to guess what the best mid-tone to expose should be (and you can adjust your dynamic range with several bracketed exposures...ala Adam's Zone system). RAW won't be 32bit color depth for quite some time, so it will clip out highlights in a scene with high dynamic range. Depending on your preferences, a gray card may be easier to spot meter. It's going to say what middle gray should be in that scene. Now on some occasions, I find that photos look better if they are slightly under or over exposed (ie, if its a night-time scene and you want to emphasize black). So I tend to meter what I think is the most important part of the scene.

 

[somawawe]

nice thing to have