Actually there was a DIY grey card thread but I didn't bother reviving it. Anyway, 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.

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:
How to use it
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.




Attached thumbnail(s)

One small note, even if you developed on kodak royal paper -matt, it can still come out to be different due to the chemical used to develop it.

thanks for sharing your discovery anyway you will soon join crazySpeakers on his 'discovery'

erm, i should get 10K posts very soon

This post has been edited by valve_300b: Jul 5 2007, 01:44 AM

wow the troll found its way to photography section

The most important thing is to ensure that your camera meter could obtain the same result that a proper grey card would provide - picture 1 vs 2.

I think the ideal here like he said in the last post is consistency, or in basic measurement lingo, Calibration

actually, you know the kind of cardboard they use to line the shirts when they are still in a package? some of those actually have a gray that's quite close to 18% gray. you'll have to look though... not all are the same.

why attach a .jpg pic instead of GIF? GIF is better suited for flat colour pics, not jpeg.

I remember last time i only use Pringles caps

If you set your camera to auto-expose, of course you're going to get the histogram in picture 2 - you'll get that even with a white sheet of paper.

for those who doesn't even know what's the grey card for, it's best to read it up.

http://www.photography.ca/phototips/meter.html

If you can look at a scene, and set the exposure "manually", nobody would ever need a light meter. The "auto exposure" is precisely a built in light meter, measuring the reflected light, and providing you a proper combination of shutter speed when given an aperture value, and vice versa. All modes, besides manual mode, uses "auto exposure"

some extra info I replied on another forum for those who still dont know why to use a grey card


This post has been edited by AlamakLor: Jul 5 2007, 12:50 PM

this is great alamaklor.
i tried it today. and it seems work fine on my snap shoot nikon camera..
especially on yellow light condition.
=)
very nice. very cheap. very easy to do it.

aha, thank you so much...been looking for a grey card but couldn't find it, will definately give this a try but do i hv to in the first place look for a properly calibrated shop to develop it?



For the one in bold, is it that we should adjust our xposure till the histrogram shift to the middle??

grey card for wat??? white balance adjust should use white paper, right??
is it for PnS Camera??

You missed my point. OK let's try approaching this another way.

You said, "The most important thing is to ensure that your camera meter could obtain the same result that a proper grey card would provide - picture 1 vs 2". How do you ensure that, without having a reference gray card on hand?

*btw, I made a mistake saying that it doesnt work with manual exposure, it actually does, you just have to ensure that whatever combination of SS and A you are using is exposed properly at 0ev. The only time I actually use manual mode is if I need to properly expose the background and light my subject with flash, and I usually rely on A/S mode to quickly get me the readings before I plug them into manual mode.

Picture 1 is a reference curve to the grey card, I do not need to have a grey card on hand as a reference but it'd sure help to clear some doubt. then again, if I had one on hand, I wouldn't bother diying it.

Picture 2 is the result of which one'd get with the diy grey card, which corresponds very well to the reference exposure a grey card would provide.

A white paper will not give you the same exposure, print the card, spot meter the grey vs white, you'd find the white to be around 1 stop brighter. Therefore, if you take a white paper and place it beside a subject that is equally pale, you'd find your subject washed out.

One caveat with the card is that the opacity is not 100% on the paper, and some light will pass through, thus affecting the measurement in some bright scenes still. I'm trying to figure out what to place behind the card to avoid this problem..hmm...

---

Added on July 5, 2007, 9:53 pmMy assumption is that shops will have machines that are calibrated to certain ICC profile that give your pictures a fair representation of colors provided that you do not opt for the color enhancement "feature". You can always print 2 cards from 2 different shop and compare if they provide the same level of exposure when being measured.

Yup, you need to fill the whole frame with the grey card. Btw, you don't just "adjust" the camera so that the historgram is in the middle and be done with it. You need to do this everytime under different lighting conditions. i.e. if you took the grey card reading indoor, and use that setting outdoor, u'd find it is messed up.

Read the links that I posted, they explained better than I did.

oh btw, I forgot to mention this. Let us assume that you are really really poor , and cannot afford more than 1 diy grey card. Then you figured that your card is always slightly off center. You are pissed, but dont wanna spend more money in finding a proper paper and developer. Simply measure the card, and adjust ur exposure using the exposure compensation feature until the histogram shifts to the center.

i.e. if your grey card measured darker than 18% and falls a little behind middle. You compensated 2/3 EV exposure and now it is in the middle. So everytime to use the card as a meaurement guideline, you know you should compensate for 2/3 exposure to get it right. Only problem with this vs getting a grey card that'd give you a correct 18% right off the bat is that in the former case, you need to always adjust the exposure compensation after taking the reading, and if your camera doesnt have an exposure compensation button handy, you need to compensate the difference in manual mode, either through shutter speed/iso/aperture

This post has been edited by AlamakLor: Jul 6 2007, 01:38 AM

That'd of course depends on how particular you are with exposure. Grey card is poorman's best way to obtain ideal exposure since the camera's meter will be calibrated to 18% with it.

Here's a great article about it:
http://www.ephotozine.com/article/Guide-to...eld-light-meter

There's also illustration of pictures taken with exposure measurement under reflected light (what built in camera meter is based on) vs measurement under incident light.

I think for convenience, you'd probably just want to rely on matrix metering. Measure a frame where the light is most evenly lited, lock ev, and recompose.

Ahh ok, this is what I was getting at. If you're going to compensate anyway, why not skip the whole printing process and just use a white card from somewhere? Being a stop more reflective it should be usable in darker environments than the gray one will be

There are edge cases where the multi-segment metering will fail to make faithful exposures (as detailed in AlamakLor's posts above). In those cases, I guess it would be useful if your LCD review is broken and you needed some reference to compare to? I shoot on film, have a gray card but it usually stays unused due to improper technique that makes the shots go awry. I use the zone system instead.

mm thanks for the tip noob here means i wont need to cary a white card around to set the white balance is it ? straight away use spot metering to aim at the gry card then shoot?

for taking scene shots ? will it help ? or just for portrait only ?
sorry if i ask noob question . thanks

Wont the grey card spoilt the whole surrounding or object ?


Doesn't quite understand on how to use it.

This post has been edited by Andy0625: Jul 8 2007, 12:56 PM