I searched for this topic, but couldn't find anything. I was wondering what a grey scale card is used for, and how it is used. From what I understand, it's for getting proper exposure when used in conjunction with the Zebra on the camera. I am also wondering why the heck the cards are so expensive to buy, is it possible to make and print my own in photoshop?
Grey Scale card
- Thread starter PDX_DVX
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Jim Brennan
VHS Member Old Skool
Re: Grey Scale card
Hey! Pay attention to this question! ;D
I'd like to know this too....
Hey! Pay attention to this question! ;D
I'd like to know this too....
pookie_old
Veteran
Re: Grey Scale card
You use an 18% gray card for adjusting the camera to get the most accurate exposure setting.
For specifics:
http://www.goshen.edu/~marvinpb/graycd.html
You use an 18% gray card for adjusting the camera to get the most accurate exposure setting.
For specifics:
http://www.goshen.edu/~marvinpb/graycd.html
10s
Veteran
Re: Grey Scale card
No, the 18% grey cards are produced under strict QC conditions by Kodak, etc., it would be luck for true renditions to come off of a printer.
18% grey is considered by scientific study/calculation of the average reflectance in nature. Its a zone 5 tone used by light meters for setting exposure. Do a web search and learn...it's the basis of exposure.
No, the 18% grey cards are produced under strict QC conditions by Kodak, etc., it would be luck for true renditions to come off of a printer.
18% grey is considered by scientific study/calculation of the average reflectance in nature. Its a zone 5 tone used by light meters for setting exposure. Do a web search and learn...it's the basis of exposure.
Barry_Green
Moderator
Re: Grey Scale card
Also, an 18% gray card is perhaps not the same as a "gray scale" card, which could be something like a series of gray chips on a card, which can be used to test exposure latitude. What Pookie described is an 18% gray card. I don't know if the original poster meant that, or meant "gray scale" card... just pointing out that those two are different.
Also, an 18% gray card is perhaps not the same as a "gray scale" card, which could be something like a series of gray chips on a card, which can be used to test exposure latitude. What Pookie described is an 18% gray card. I don't know if the original poster meant that, or meant "gray scale" card... just pointing out that those two are different.
pookie_old
Veteran
Re: Grey Scale card
True Barry, I assumed the 18% gray card.
True Barry, I assumed the 18% gray card.
XCheck
Veteran
Re: Grey Scale card
Actually, an 18% grey card is only about 10 bucks, so I think it's less expensive than what it would cost you to produce one yourself.
While I've found 18% G.C. more than adequate in still photography, all the tests I've done with DVX tell me that it's simply not enough. You have different gamma settings, and for each the mid-grey will have different IRE levels. If you try to set your G.C. exposure to 50% with cine gamma, for sure your highlights will be blown out. Another reason it's not enough (in contrast to still photography) is the much lower exposure latitude of video (even with cine gamma). 18% GC is calibrated to be in the middle of the 10-zone exposure scale. The scale is much narrower for video, so 18% GC is more like about 40-45%. As I said, this differs for different gamma setting.
So the grey scale is more useful because it allows you to set exposure according to the highlights (make sure they don't blow out), and also set the gamma to your preference. Barry's book and DVD is excellent resource on how to do it.
Then there are color chip cards, which is another story altogether. I got a Macbeth card, which is worth every penny (about $120 Canadian), and it also includes six neutral grey chips from white to black. You cannot easily reproduce it by printing, but it comes with a little chart of RGB values corresponding with the chips. I created a photoshop version of it and use it to visually calibrate my PC monitor and for color correction - but I am still learning how to do it in a most efficient way, so I don't have a cookbook on how to do it.
Actually, an 18% grey card is only about 10 bucks, so I think it's less expensive than what it would cost you to produce one yourself.
While I've found 18% G.C. more than adequate in still photography, all the tests I've done with DVX tell me that it's simply not enough. You have different gamma settings, and for each the mid-grey will have different IRE levels. If you try to set your G.C. exposure to 50% with cine gamma, for sure your highlights will be blown out. Another reason it's not enough (in contrast to still photography) is the much lower exposure latitude of video (even with cine gamma). 18% GC is calibrated to be in the middle of the 10-zone exposure scale. The scale is much narrower for video, so 18% GC is more like about 40-45%. As I said, this differs for different gamma setting.
So the grey scale is more useful because it allows you to set exposure according to the highlights (make sure they don't blow out), and also set the gamma to your preference. Barry's book and DVD is excellent resource on how to do it.
Then there are color chip cards, which is another story altogether. I got a Macbeth card, which is worth every penny (about $120 Canadian), and it also includes six neutral grey chips from white to black. You cannot easily reproduce it by printing, but it comes with a little chart of RGB values corresponding with the chips. I created a photoshop version of it and use it to visually calibrate my PC monitor and for color correction - but I am still learning how to do it in a most efficient way, so I don't have a cookbook on how to do it.
Re: Grey Scale card
Do you use the grayscale elements of your Macbeth color chart with zebra? I would think that the lower value grays and white chip could be used to quick effect for dialing-in your iris [when you don't have a scope / DV Rack at your disposal].
This operation would follow appropriate ND selection and whitecard balance.
e
Do you use the grayscale elements of your Macbeth color chart with zebra? I would think that the lower value grays and white chip could be used to quick effect for dialing-in your iris [when you don't have a scope / DV Rack at your disposal].
This operation would follow appropriate ND selection and whitecard balance.
e
Jim Brennan
VHS Member Old Skool
Re: Grey Scale card
It never ceases to amaze me how ignorant I am of the finer points of filmmaking. :-/
It never ceases to amaze me how ignorant I am of the finer points of filmmaking. :-/
Soliton
Well-known member
Re: Grey Scale card
the_other_Mark,
The DVRack I bought came with the gray scale card, not a dedicated 18% gray. Is the gray border around the gray scales at 18%? Or did I my package come without an 18% 'gray card'?
Could be we just have a confusion of terminology here :-/
the_other_Mark,
The DVRack I bought came with the gray scale card, not a dedicated 18% gray. Is the gray border around the gray scales at 18%? Or did I my package come without an 18% 'gray card'?
Could be we just have a confusion of terminology here :-/
Re: Grey Scale card
My mistake, Soliton. I meant "gray scale card," not "18% gray card." Given the fact that this thread contains perfectly lucid definitions of the two types of cards, I have no legitimate excuse--so I'll borrow some bogus ones: "I ran outta gas. I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from outta town. Someone stole my car. There was an earthquake, a terrible flood, locusts. It wasn't my fault!! I swear to God!!"
As for the border on the gray scale card, it's 50%.
My mistake, Soliton. I meant "gray scale card," not "18% gray card." Given the fact that this thread contains perfectly lucid definitions of the two types of cards, I have no legitimate excuse--so I'll borrow some bogus ones: "I ran outta gas. I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from outta town. Someone stole my car. There was an earthquake, a terrible flood, locusts. It wasn't my fault!! I swear to God!!"
As for the border on the gray scale card, it's 50%.
Jim Brennan
VHS Member Old Skool
Re: Grey Scale card
Aww Jake...Jake honey..
Aww Jake...Jake honey..
