[sany]

Are the Gray cards that are sold useful in practical day to day photography?
this I am asking because, when we meter we can for a maximum stretch our hands holding the card at an arms length to meter the card but what if my subject is around 5 m away - will metering the card in arms length is sufficient for the exposure for a subject 5 m away?

[Parallax]

Distance doesn't matter when metering reflected light. The card would meter the same at 12 inches and 12 feet assuming that you are metering only the card, and not any of the area around the card.
One of the things I use one for frequently is shooting shaded objects at a distance when the subject occupies too small a portion of the FOV for even spot metering to isolate.

[sany]

Distance doesn't matter when metering reflected light. The card would meter the same at 12 inches and 12 feet assuming that you are metering only the card, and not any of the area around the card.

...but the lighting difference may vary from arms distance and near the subject which might give different light values isnt it?

[Parallax]

Yes, that's possible; but the gray card, IMHO, gives you the best chance of getting it right.

[Just1MoreDave]

If the gray card doesn't fill very much of the frame, you could use your spot meter on just the card. The spot meter area is marked on the focus screen with brackets. Metering will be done on just the card, so hold the card at or near the important part of the subject. This method will ignore any light except on the card, so keep that in mind. And don't forget to switch metering modes for tthe next shots. Spot metering is useful if you do it right.

[sany]

If the gray card doesn't fill very much of the frame, you could use your spot meter on just the card. The spot meter area is marked on the focus screen with brackets. Metering will be done on just the card, so hold the card at or near the important part of the subject. This method will ignore any light except on the card, so keep that in mind. And don't forget to switch metering modes for tthe next shots. Spot metering is useful if you do it right.

...and while using Pentax 'M' lens, I believe that is the only option (spot metering), am I right?

thanks

[Just1MoreDave]

No, you should have spot and center-weighted.

Since I just looked it up in the manual, switching metering modes is on page 116. You'll probably see Multi-Segment grayed out if the M series lens is on the camera.

[RioRico]

Sany, you keep asking good questions! Keep it up!

Back in my film days (some decades ago) I used the gray card that was built into my little black KODAK MASTER PHOTOGUIDE book. Alas, that is gone now. I no longer use gray cards because for me, it's not as necessary with a digital camera -- exposures are much easier to review and adjust. The camera's metering system is built to expose for 18% gray. The card is 18% gray. Reading (metering) off the card gives you an exposure setting that is correct for the light in which the card is held. That is fine if your subject is lit the same way, not so fine if it isn't.

Without a card, I used other metering tricks. My cameras then were center-weighted, at best. (Some weren't even that specific.) If I was going to shoot someone whose skin was about the same shade as mine, I would meter off my hand. Or I would meter off my sleeve, or the ground near me, or something nearby that looked about the same shade as the subject. That always worked for me with B&W film.

A gray card can be very useful when exposure accuracy is critical and you have control of light and subject. But mostly I just shoot, chimp (review the shot), adjust as needed, and shoot again.

[tuco]

Grey cards and digital are still useful for color balance.

[adr1an]

Grey cards and digital are still useful for color balance

+1

I shoot Raw, so I know it can be all fixed in Post.. but when I recently punched out about 100 'product' pictures (if you can call them that ) of a friends chocolates I used a grey card to set a Custom WB on the camera. Reason was it was all lit with about 4 speedlites, all on Manual in a controlled environment with little to no ambient..

I could have just used the one reference frame to then sync the WB across all the images in Post.. but its another thing to do in post that I just wanted to avoid. Also given I was shooting Milk, Dark and White chocolates - AWB was all *over* the shop...

By taking the extra 1 min to setup Custom WB I then had consistent colours across all the chocolate shots and I didn't have to spend ages trying to make Milk Chocolate look Milk again and get the White chocolate to look the proper 'white' of the chocolates in Post... My batching was a simple denoise and output sharpen and all 107 images were done...

[billtin59]

You don't need a gray card, grass reflects approx. 18% of light, as does the blue sky away from the sun, asphalt also work in a pinch provided it isn't t new or freshly sealed.

[Pentikonian]

As billtin59 mentioned, there are other ways to meter...

If you are interested and haven't already checked out the book, Understanding Exposure by Bryan Peterson has multiple pages where he discusses metering, the 18% gray issue, and multiple different ways to meter without a gray card.

[kanzlr]

I use a greycard for whitebalance if I mix light.
When I do outdoor portraiture I usually have a flash in a softbox (or two) and just in case, I take every odd shot with the greycard in it to have a bullet proof white balance to work with in RAW.

but really, thats the only thing I use it for

[noaslplease]

I got a free gray card from Wilsonart a week ago... Free shipping also. If I find the link, I'll share it!

Found the link. North Sea is the correct 18 percent shade of gray.
Make sure you select the 8 x 10 card.
Shipping is free, and no need to supply your credit info. Pretty handy.
https://samples.wilsonartcontract.com/p-273-north-sea-d90-60.aspx