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FORUMS Post Processing, Marketing & Presenting Photos RAW, Post Processing & Printing 
Thread started 13 Jul 2009 (Monday) 18:39
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QP101 Gray Card questions

 
Guts311
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Jul 13, 2009 18:39 |  #1

Hi, I just received this gray card from Adorama: http://www.adorama.com …?searchinfo=gra​y+card+101 (external link)

Although I know the basics of correctly doing a custom white balance (before shooting in-camera, or in PP), I guess I am looking for a better understanding of how to correctly use this new item.
I realize that the middle lighter gray is the typical color to use for WB, but I don't know when you would use the darker gray (it's not completely black like it says) or white (if ever).

Also, say I am going to take one photo of the card for doing the custom WB later in PP. Do I take a close-and-in-focus-as-possible shot of the middle gray color and use that whole photo's WB for the CWB? Or do I place the whole card further away from the lens, somewhere in the scene so that it is more in the same lighting as the subject and select the gray portion with the WB dropper later? Do I take that original card photo with Auto WB set or a different WB (In RAW and JPEG situations)? I've read both..

How do you really do the in-camera CWB setting when you cannot use an eyedropper to select the specific gray card area for WB? Holding the card way up close filling the whole frame doesn't work because the lighting is different there than in the actual scene location (probably not as close to the lens).

Thanks in advance.




  
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Guts311
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Jul 13, 2009 19:42 |  #2

bump :)




  
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PhotosGuy
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Jul 13, 2009 22:10 |  #3

"somewhere in the scene so that it is more in the same lighting as the subject and select the gray portion with the WB dropper later?" is what I'd suggest.

Do I take that original card photo with Auto WB set or a different WB (In RAW and JPEG situations)? I've read both..

White balance not ...balanced? What am I doing wrong?

Personally, for normal "walk around" shots outside, I use a WB Pre-set & shoot RAW. In a studio, I use a Custom WB.


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Guts311
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Jul 13, 2009 22:11 |  #4

When you say a WB preset, you mean one of the selections on the camera besides AWB? Like Sunny, etc..?

Since you use CWB in studio, can you answer any of my above questions pertaining to doing CWB with a card?




  
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BigAlz1
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Jul 13, 2009 23:41 |  #5

Looks like your style of gray card is meant for a dropper/picker to be used inside of a program like DPP or PS. It has the black, white, and gray portions all on one strip. This type of card needs to be set in the scene and focused and shot just like the subject (I place mine on the subject or have them hold it if it's a human).

Then in PP you use (for example) the levels adjustment tool in PS and use the black dropper on the black portion and the white dropper on the white then the gray on the gray.

If you wanting to set an "in camera CWB" you really need a larger sheet of just 18 percent gray card or just a white one. Many people use either or.
Good thing about the white/gray/black strip like you have is that you can use your WB dropper in either DPP or PS and click on either the gray or the white to see witch one gives you the feel of the correct WB.




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tzalman
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Jul 14, 2009 00:29 |  #6

I've been using the QP card for years. Standing in the same light as the subject I hold the card at arm's length and shoot it without focusing (OOF blur dithers the color). Since I always shoot RAW the camera WB is irrelevent, usually AWB. In the converter I zap it with the dropper on the near-white (right side) section.
If I were to ever shoot jpg (hard to imagine) I would do pretty much the same. It is only needed to fill the Partial Metering circle for a CWB.


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amonline
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Jul 14, 2009 01:19 |  #7

In laymen's terms - the gray is for WB or color balance and the white and black are for clipping levels.

So, in DPP or whatever (where you choose your WB), click the gray. Then, use the white and black to find over exposure of the whites and (if desired) where your blacks begin. The white should be used during the shoot to gauge exposure.

Generally, most people do not mess with the blacks. Usually, clicking the gray (WB) and adjusting the exposure to your liking is about all anyone does. If the card is used properly during the shoot, all you need to do is click the gray in post.

Most people that use these generally are shooting commercial work or things where WB is super important. Photogs shooting people (as well as commercial) usually use the Gretagmacbeth card instead. (for skin tones, etc)

Everyone here has provided great info. My addition is just the basic description of what you should be doing.




  
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PhotosGuy
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Jul 14, 2009 09:30 |  #8

When you say a WB preset, you mean one of the selections on the camera besides AWB? Like Sunny, etc..?

Yes.

Since you use CWB in studio, can you answer any of my above questions pertaining to doing CWB with a card?

It's in the first sentence of the link I gave you? Was that not clear to you, & if so, what part of it didn't you understand?
I don't use a card like you bought. It makes no sense to me as I also explained in that post. To use your card, the above posts by BigAlz1 & others explain the procedure.


FrankC - 20D, RAW, Manual everything...
Classic Carz, Racing, Air Show, Flowers.
Find the light... A few Car Lighting Tips, and MOVE YOUR FEET!
Have you thought about making your own book? // Need an exposure crutch?
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Guts311
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Jul 14, 2009 09:32 |  #9

No I saw the post, I just had several small detail questions in my OP, but no biggie. I'll figure it out!

Thanks.




  
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nicksan
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Jul 14, 2009 09:46 as a reply to  @ Guts311's post |  #10

If it is what I think it is, I have something similar called the WhiBal card. It is used to correct WB in post.

You basically take a reference shot under the same lighting conditions your subject will be in. There's no hard set rule on how much of the frame to fill since this is not CWB. The only thing you need to be careful about is that any reflection from the light is not affecting the readings.

Then shoot the rest of the series. Then in post, use the "WB drop tool" on the reference image by clicking anywhere on the neutral gray area, which will effectively correct your WB. Then apply to the rest of the series.

The important thing to remember, which sometimes gets lost in the mix, is you need to take your camera out of AWB and set it to something with a constant color tempurature so that you get consistent WB settings...




  
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Guts311
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Jul 14, 2009 09:56 |  #11

nicksan wrote in post #8277833 (external link)
The important thing to remember, which sometimes gets lost in the mix, is you need to take your camera out of AWB and set it to something with a constant color tempurature so that you get consistent WB settings...

But why does this matter if you are changing the RAW file's WB to a CWB afterwards anyway? Even if all photos in the series were taken with different preset WBs, wouldn't the applied CWB change them all to match in PP anyway?




  
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nicksan
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Jul 14, 2009 10:14 |  #12

Think about it for a moment. When you have your camera in AWB, having the grey card in the frame may give you a different WB reading than without it. This is exactly what you don't want because then when you apply the WB to the rest of the series in post, things may be off. You are letting the camera decide.

Try this for youself. Put the grey card somewhere, perhaps the floor, and shoot a frame in AWB. Then shoot a frame without the grey card. See if the tempurature looks the same. Also, correct the WB on the reference shot, then apply to the second image and see if the tempurature looks the same. YMMV when it comes to all this however...

What you want is a constant tempurature setting...a controlled setting, so to speak. You can use any of the WB presets or the "K" setting to achieve this. This way you know in post, all of your images are the same temperature and you can then be confident that applying the WB correction to the series will yield the same results.

Also, just in case it wasn't obvious, you'd want to take a reference shot every time lighting changes. Also, provided you have some kind of neutral color in the frame, yes, it's pretty easy to correct WB in post even without the reference shot.

Guts311 wrote in post #8277902 (external link)
But why does this matter if you are changing the RAW file's WB to a CWB afterwards anyway? Even if all photos in the series were taken with different preset WBs, wouldn't the applied CWB change them all to match in PP anyway?




  
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nicksan
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Jul 14, 2009 10:20 as a reply to  @ nicksan's post |  #13

Another thing. You can also use the silver "Canon" logo on a Canon lens cap as a make shift gray reference "card".

I had the camera in "K" IIRC. (5200K default I think...)

Before:

IMAGE: http://nicksan.zenfolio.com/img/v0/p683872232-4.jpg

Then I used the WB drop tool and clicked on an area in the "Canon" sliver logo...

IMAGE: http://nicksan.zenfolio.com/img/v0/p732760160-4.jpg

Pretty easy...and actually VERY close to the readings I get on my WhiBal card. The only issue is that the Canon log is kind of reflective so you need to be extra careful not to get any glare off of it which will affect the readings.



  
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kirkt
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Jul 14, 2009 10:42 |  #14

The size of the strip of the white-gray-black card makes it pretty tough to use for setting a custom white balance in camera, so it is pretty much a reference for RAW images that will be adjusted in post (although @tzalman states he does that, above, so go for it!). The gray is also stated as an 18% gray, which is what your metering system assumes the scene to be when it gives you a reflectance meter reading TTL. So, you can use the strip for WB in post, but you could also spot meter the gray swatch to get a reflectance meter reading from your camera under the particular lighting conditions, should you need to. Remember to place the card in the scene lighting in such a way that it is close to the subject but there is no glare on the card, otherwise you won't get a very useful reading.

The black and white swatches are there to give you an idea of the black and white points in your exposure. This, like the gray swatch, is pretty dependent on the reflectance of that card compared to your subject though, so it is useful but you may need to introduce some exposure compensation to accommodate specific lighting conditions.

Some people prefer to shoot RAW with a preset WB selected that is close to the actual lighting, regardless of whether or not they intend to adjust WB in post. Personally, I have found excellent results with the Lastolite Ezybalance collapsible gray target to set up a custom WB in-camera. It provides a reference in RAW post, but it usually eliminates that step in post because the image is already correctly balanced when the image is imported into Lightroom or ACR, where my default WB is set to "As Shot". It is also a larger target than my WhiBal card, so local lighting concentrations don't dominate the image of the target as opposed to a smaller target.

Good luck!

Kirk


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Guts311
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Jul 14, 2009 10:48 |  #15

nicksan wrote in post #8278019 (external link)
Think about it for a moment. When you have your camera in AWB, having the grey card in the frame may give you a different WB reading than without it. This is exactly what you don't want because then when you apply the WB to the rest of the series in post, things may be off. You are letting the camera decide.

Try this for youself. Put the grey card somewhere, perhaps the floor, and shoot a frame in AWB. Then shoot a frame without the grey card. See if the tempurature looks the same. Also, correct the WB on the reference shot, then apply to the second image and see if the tempurature looks the same. YMMV when it comes to all this however...

What you want is a constant tempurature setting...a controlled setting, so to speak. You can use any of the WB presets or the "K" setting to achieve this. This way you know in post, all of your images are the same temperature and you can then be confident that applying the WB correction to the series will yield the same results.

Also, just in case it wasn't obvious, you'd want to take a reference shot every time lighting changes. Also, provided you have some kind of neutral color in the frame, yes, it's pretty easy to correct WB in post even without the reference shot.

I see. Thanks for the replies guys.

Any recommendation on which preset WB to use or which K temperature to set it at for every pic in a series? I guess with RAW it doesn't matter as long as they're the same...




  
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QP101 Gray Card questions
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