Exposure Difference: Which is correct?

Yeah, but with only one watch, he can't tell you the range of what the correct time might be.

Chrigu said:

What was the old saying? A man with one watch always knows the
time, a man with two is never sure?

(Or something like that.)

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Here's what Chuck Westfall has said on the subject (taken from RobG's forum):

1. Obtain a Kodak Q-14 Color Separation Guide and Gray Scale (CAT 152 7662) from your photo dealer.

2. Set up the Gray Scale indoors in typical overhead room lighting and mount your D30 on a tripod. Position the camera roughly 5 feet from the target and parallel to it. Zoom the lens to fill the frame from left to right. Aim the central focusing point at zone M on the Gray Scale. Make sure the subject is focused, then shut off the AF.

3. Set the D30 to Manual mode with Partial metering. (DO NOT use an automatic exposure mode.) Other camera settings will be manually selected center focusing point, auto white balance, single frame advance or self-timer, IS0 100, and any JPEG setting you like.

4. Set an aperture of f/8 and, while looking through the viewfinder, adjust the shutter speed until the exposure level indicator lines up in the middle of the exposure level scale.

5. Take a series of non-flash exposures at, over and under the D30's recommended exposure level, using shutter speed as your adjustment. (Note: the camera defaults to 1/2 stop settings, but you can change this to 1/3 stops if you like by means of C.Fn. 4.

6. Examine the resulting images in Photoshop, using the Info palette set for Grayscale (K) values. The K reading for Zone M should be at about 55%. Check your images and see which image matches this figure most closely.

7. The acceptable deviation is + - 5%.

Unfortunately, this doesn't help me know what a Gray Card should read.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

If you look deep into the battery compartment do you see a series of small gold-colored electrical contacts? They insert what is sometimes called a horn into the compartment which powers the camera and allows adjustment of a variety of parameters. No need to take the beast apart. But it must be done by Canon. Severe problems would mandate a take-apart to expose the internal circuit boards. I don't think you have that problem.

And, no, the electronics do not drift as some think. They are rock solid and will be for long after you have graduated to the next camera. The meter sensor itself can be affected by dust and grease but I'm sure you take care of the camera a lot better than most.

DavidP said:

Al Pacheco said:

But all that aside....I'm still surprised your fe-furb is off a
bit. Could it be the previous owner requested Canon to adjust it?

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

I think that the Sekonic almost agrees with the original 1D. Here's my logic:

Sekonic reads 1/25
original 1D reads 1/40
refurb 1D reads 1/60

Remember that you're supposed to open up a camera by 1/2 stop when reading a gray card (since the camera meter reads 13% gray instead of the 18% gray card). This is for a front-lit object.

If I open up the 1D by 1/3 stop, I'd be at 1/30. If I open up the 1D by 2/3 stops, I'd be at 1/25 (matching the Sekonic).

More than likely, the correct value of exposure is (in 1/3 stop increments) 1/25 second. For this correct value of exposure, the camera should read 1/30. This would mean that the original 1D is over-exposing by 1/3 stop, and that the refurb 1D is over-exposing by 1 full stop.

This assumes that the Sekonic is setup to read proper exposure, and that the camera needs to be opened up 1/2 (or 1/3) stop from a gray card reading for proper exposure.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

That's what I think, too.

See my post from a minute or so ago (way down the list). I think the original 1D is probably under-exposing by 1/3 stop (at most), and that the refurb 1D is under-exposing by a full stop. (Unfortunately, I said over-exposing in the post - DOH! -- gotta go correct that).

Anyway, one thing I don't like about the 1D (the D30 didn't do this) is that when you put a flash on the camera, the ambient exposure gets reduced by 2/3 stops when light levels are low (like inside a house). I wonder if they can turn off this "feature" ?

Al Pacheco said:

If you look deep into the battery compartment do you see a series
of small gold-colored electrical contacts? They insert what is
sometimes called a horn into the compartment which powers the
camera and allows adjustment of a variety of parameters. No need to
take the beast apart. But it must be done by Canon. Severe
problems would mandate a take-apart to expose the internal circuit
boards. I don't think you have that problem.

And, no, the electronics do not drift as some think. They are
rock solid and will be for long after you have graduated to the
next camera. The meter sensor itself can be affected by dust and
grease but I'm sure you take care of the camera a lot better than
most.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

I hate it when I say over when I mean under. LOL.

That second to last paragraph should read:

More than likely, the correct value of exposure is (in 1/3 stop increments) 1/25 second. For this correct value of exposure, the camera should read 1/30. This would mean that the original 1D is under-exposing by 1/3 stop, and that the refurb 1D is under-exposing by 1 full stop.

DavidP said:

I think that the Sekonic almost agrees with the original 1D.
Here's my logic:

Sekonic reads 1/25
original 1D reads 1/40
refurb 1D reads 1/60

Remember that you're supposed to open up a camera by 1/2 stop when
reading a gray card (since the camera meter reads 13% gray instead
of the 18% gray card). This is for a front-lit object.

If I open up the 1D by 1/3 stop, I'd be at 1/30. If I open up the
1D by 2/3 stops, I'd be at 1/25 (matching the Sekonic).

More than likely, the correct value of exposure is (in 1/3 stop
increments) 1/25 second. For this correct value of exposure, the
camera should read 1/30. This would mean that the original 1D is
over-exposing by 1/3 stop, and that the refurb 1D is over-exposing
by 1 full stop.

This assumes that the Sekonic is setup to read proper exposure, and
that the camera needs to be opened up 1/2 (or 1/3) stop from a gray
card reading for proper exposure.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

I remember there was great debate on the 13 vs 18% grey card andwhat the cameras were truly calibrated against almost a year ago on this forum. I do not think therewas a definitive conclusion.

DavidP said:

I think that the Sekonic almost agrees with the original 1D.
Here's my logic:

Sekonic reads 1/25
original 1D reads 1/40
refurb 1D reads 1/60

Remember that you're supposed to open up a camera by 1/2 stop when
reading a gray card (since the camera meter reads 13% gray instead
of the 18% gray card). This is for a front-lit object.

If I open up the 1D by 1/3 stop, I'd be at 1/30. If I open up the
1D by 2/3 stops, I'd be at 1/25 (matching the Sekonic).

More than likely, the correct value of exposure is (in 1/3 stop
increments) 1/25 second. For this correct value of exposure, the
camera should read 1/30. This would mean that the original 1D is
over-exposing by 1/3 stop, and that the refurb 1D is over-exposing
by 1 full stop.

This assumes that the Sekonic is setup to read proper exposure, and
that the camera needs to be opened up 1/2 (or 1/3) stop from a gray
card reading for proper exposure.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Camera meters read 13% gray. PERIOD. (OK, maybe it's 12 or 12.5%)

We have a Mr. Ansel Adams to thank for Kodak printing 18% gray cards instead of the proper ones. Simply because 18% gray matched his Zone V. All his fine art shouldn't have given him the power to screw over photographers from that point forward, though, IMO. Shame on Kodak and Mr. Ansel.

Light meters should also read 13% gray. But since they're usually adjustable, you can change that by + - a stop.

There's a REASON that the Kodak Gray Card tells you to open up 1/2 stop from the camera reading when exposing for a front-lit object. It's because the danged card isn't the right card for setting camera exposure. Thanks a LOT Kodak and Ansel.

mark kay said:

I remember there was great debate on the 13 vs 18% grey card
andwhat the cameras were truly calibrated against almost a year ago
on this forum. I do not think therewas a definitive conclusion.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

a man with many watches. There is no guarantee that they all won't be early or late. Besides, accurate time doesn't exist, anyway. It's a continuous variable. There can only be a range of time at best (x time + or - x time).

David,

I have seen several threads telling you to take an Expodisc outside, in daylight, point it directly at the sun, and take a light reading.

If I recall, at ISO100, the reading should be 1/125 at f16. You could do the same test with both cameras and the light meter and have a good starting point.

It sounds like all that you need is a good baseline. This would give it to you.

Good luck!

Mark

Sounds nice, but I guarantee you that you'll get different readings than 1/125 depending on the time of year.

Dr_ML said:

I have seen several threads telling you to take an Expodisc
outside, in daylight, point it directly at the sun, and take a
light reading.

If I recall, at ISO100, the reading should be 1/125 at f16. You
could do the same test with both cameras and the light meter and
have a good starting point.

It sounds like all that you need is a good baseline. This would
give it to you.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

http://www.weather.com/weather/local/USTX0617?lswe=houston%2C+tx&lswa=WeatherLocalUndeclared&whatprefs=

Ain't gonna be sunny here for at least a week.

Dr_ML said:

I have seen several threads telling you to take an Expodisc
outside, in daylight, point it directly at the sun, and take a
light reading.

If I recall, at ISO100, the reading should be 1/125 at f16. You
could do the same test with both cameras and the light meter and
have a good starting point.

It sounds like all that you need is a good baseline. This would
give it to you.

Good luck!

Mark

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Ansel Adams eventually felt that the 18% card was at the border of his zones #5 & 6...not the center of zone 5. Middle grey standards (which you won't find in a camera store) usually have reflective densities of about 0.95 to 1.00. That grey card is at about 0.75. About 2/3 brighter. But nobody is in charge anymore....ANSI is AMERICAN only and ISO standards carry little weight. How does Canon do it? Who knows.

You need to characterize your camera/software and then you'll have a better understanding about how it treats your grey card. If you want to have a low-key image then the card will end up having low values. High-key will send it up the scale. There's no basis in the myth that you should end up with R=G=B=127.

If you try to match it to Photoshop and the standard color spaces like Adobe RGB(1998) or sRGB then it should fall somewhere between 110 and 120. But then your software will have an impact...saturation and contrast will seesaw the values around a bit. Exposure and white balance get tossed in,too.

DavidP said:

We have a Mr. Ansel Adams to thank for Kodak printing 18% gray
cards instead of the proper ones. Simply because 18% gray matched
his Zone V. All his fine art shouldn't have given him the power to
screw over photographers from that point forward, though, IMO.
Shame on Kodak and Mr. Ansel.

Light meters should also read 13% gray. But since they're usually
adjustable, you can change that by + - a stop.

There's a REASON that the Kodak Gray Card tells you to open up 1/2
stop from the camera reading when exposing for a front-lit object.
It's because the danged card isn't the right card for setting
camera exposure. Thanks a LOT Kodak and Ansel.

mark kay said:

I remember there was great debate on the 13 vs 18% grey card
andwhat the cameras were truly calibrated against almost a year ago
on this forum. I do not think therewas a definitive conclusion.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

I apologize if I'm repeating someone else but how do you sample the RGB colors? If you used photoshop what size sample did you use for the eye dropper (1, 3x3, 5x5)?

DavidP said:

It appears that my refurb 1D and original 1D are exposing
differently. The refurb underexposes by 2/3 relative to my new
one.

In the following photographs, I exposed using Av with spot-metering
on the gray card. I have put the R,G,B values of the gray card
(along with the R,G,B values of a white sheet of Bright White
Injket Paper by HP) on the images.

Which camera is exposing correctly? (Or are both incorrect?).
Does anybody who has a known properly exposure meter on the 1D know
the correct values for R,G,B of a gray card?





--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

I actually selected a very large rectangle over each area, then did a Image . . Histogram to find the average luminosity.

Timothy Schaffer said:

I apologize if I'm repeating someone else but how do you sample the
RGB colors? If you used photoshop what size sample did you use for
the eye dropper (1, 3x3, 5x5)?

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Al Pacheco said:

But all that aside....I'm still surprised your fe-furb is off a
bit. Could it be the previous owner requested Canon to adjust it?

DavidP said:

Al Pacheco said:

DavidP said:

PS - in Av or Tv, the meter actually reads (internally) to the
nearest 1/8 stop. Not 1/3 or 1/2. It just displays in values of
1/3 or 1/2.

Click to expand...

And that's what they call...snake oil! Doesn't matter if the meter
can read down to a hundredth of a stop...if the hardware can only
do thirds then that's what you have. I've tested a friend's 1V
for him...(and I believe the 1V is the film world's 1D/1Ds) ...and
1/3 stop is all you get.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Click to expand...

Al,

My understanding and experience are the following...

The hardware can only be SET to 1/3 stops, but if you are in Av mode the shutter speeds are set by the camera to .1EV resolution (at least on some of the cameras), and it is stored that way (the actual shutter speeds) in the EXIF...the actual exposure. That is way in YarcPlus you will sometimes see shutter speeds that are not at the 1/3 EV points. Those are the REAL exposures that were shot. Most software rounds the displayed values (as does the camera), but the EXIF has the real deal stored internally.

--
Regards,

Michael Tapes
(YarcPlus - Archive Creator)
http://www.PictureFlow.com
http://www.michaeltapes.com

I don't have experience with a 1D or a 1Ds.

MichaelT said:

Al Pacheco said:

But all that aside....I'm still surprised your fe-furb is off a
bit. Could it be the previous owner requested Canon to adjust it?

DavidP said:

Al Pacheco said:

DavidP said:

PS - in Av or Tv, the meter actually reads (internally) to the
nearest 1/8 stop. Not 1/3 or 1/2. It just displays in values of
1/3 or 1/2.

Click to expand...

And that's what they call...snake oil! Doesn't matter if the meter
can read down to a hundredth of a stop...if the hardware can only
do thirds then that's what you have. I've tested a friend's 1V
for him...(and I believe the 1V is the film world's 1D/1Ds) ...and
1/3 stop is all you get.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Click to expand...

Al,

My understanding and experience are the following...

The hardware can only be SET to 1/3 stops, but if you are in Av
mode the shutter speeds are set by the camera to .1EV resolution
(at least on some of the cameras), and it is stored that way (the
actual shutter speeds) in the EXIF...the actual exposure. That is
way in YarcPlus you will sometimes see shutter speeds that are not
at the 1/3 EV points. Those are the REAL exposures that were shot.
Most software rounds the displayed values (as does the camera), but
the EXIF has the real deal stored internally.

--
Regards,

Michael Tapes
(YarcPlus - Archive Creator)
http://www.PictureFlow.com
http://www.michaeltapes.com

Click to expand...

David,

From my own experiences, I'd trust the Sekonic. It is the most accurate way to meter light that I have.

I disagree that they come out of the factory out of calibration too often (of course, anything can happen once in a while), I think that the reason a lot of people feel that their meter is out of whack is because they are mostly used with older MF equipment. The mechanical shutters in some of these cameras tend to differ from unit to unit, especially as some have not been serviced and adjusted in many years. This, in combination with different film emulsions and people's differing preferences as to what "correct exposure" should look like, sometimes results in people feeling that their meter is "out"... At least that is the way it appears to me after reading the threads over at the Sekonic Users Forum.

So, once again: Go with the Sekonic. I'd bet it's the closest to the correct exposure! If your original 1D underexposes by 1/3 of a stop, it could only be that it's being conservative so as not to blow out the highlights (the Canon DSLRs are famous for that). ! 3 of a stop shouldn't really matter anyway, but if you really want to, you can easily compensate for it.

As to why your refurb is another 2/3 of a stopp off, I have no idea...

DavidP said:

I think that the Sekonic almost agrees with the original 1D.
Here's my logic:

Sekonic reads 1/25
original 1D reads 1/40
refurb 1D reads 1/60

Remember that you're supposed to open up a camera by 1/2 stop when
reading a gray card (since the camera meter reads 13% gray instead
of the 18% gray card). This is for a front-lit object.

If I open up the 1D by 1/3 stop, I'd be at 1/30. If I open up the
1D by 2/3 stops, I'd be at 1/25 (matching the Sekonic).

More than likely, the correct value of exposure is (in 1/3 stop
increments) 1/25 second. For this correct value of exposure, the
camera should read 1/30. This would mean that the original 1D is
over-exposing by 1/3 stop, and that the refurb 1D is over-exposing
by 1 full stop.

This assumes that the Sekonic is setup to read proper exposure, and
that the camera needs to be opened up 1/2 (or 1/3) stop from a gray
card reading for proper exposure.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

--
Regards,

Rudi
http://www.rudiphoto.net/

It looks to me like it's nothing to worry about. How do real pictures look?

I printed a grey card at RGB 128,128,128 and compared it with a grey card that came with a photography book - it was dead on. But it might be blind luck as well, since my printer color reproduction might be off.

DavidP said:

It appears that my refurb 1D and original 1D are exposing
differently. The refurb underexposes by 2/3 relative to my new
one.

In the following photographs, I exposed using Av with spot-metering
on the gray card. I have put the R,G,B values of the gray card
(along with the R,G,B values of a white sheet of Bright White
Injket Paper by HP) on the images.

Which camera is exposing correctly? (Or are both incorrect?).
Does anybody who has a known properly exposure meter on the 1D know
the correct values for R,G,B of a gray card?





--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Actually, the first 1D and the Sekonic probably differ by only 1/6 stop.

The original 1D meter reads 2/3 underexposed compared to the Sekonic. But, you're supposed to open up 1/2 stop using a gray card.

4/6 - 3/6 = 1/6

So, the two meters are within 1/6 stop. That's pretty darned close, if you think about it. Especially since the meters can only display in 1/3 stops (the way I have them both set).

PS -- how's that 28-70/2.8 ?

Are you gonna go take some pictures of the Wilkinsons for me when they're in your area?

rudiphoto said:

From my own experiences, I'd trust the Sekonic. It is the most
accurate way to meter light that I have.

I disagree that they come out of the factory out of calibration too
often (of course, anything can happen once in a while), I think
that the reason a lot of people feel that their meter is out of
whack is because they are mostly used with older MF equipment. The
mechanical shutters in some of these cameras tend to differ from
unit to unit, especially as some have not been serviced and
adjusted in many years. This, in combination with different film
emulsions and people's differing preferences as to what "correct
exposure" should look like, sometimes results in people feeling
that their meter is "out"... At least that is the way it appears to
me after reading the threads over at the Sekonic Users Forum.

So, once again: Go with the Sekonic. I'd bet it's the closest to
the correct exposure! If your original 1D underexposes by 1/3 of a
stop, it could only be that it's being conservative so as not to
blow out the highlights (the Canon DSLRs are famous for that). ! 3
of a stop shouldn't really matter anyway, but if you really want
to, you can easily compensate for it.

As to why your refurb is another 2/3 of a stopp off, I have no
idea...

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise