ok..I got to get this right now...exposure question

wildviper

Hi All,

I have been shooting for a while now and always am trying to learn how to get better exposures. While I am able to "save" a lot of images since I use RAW...its time I understand something very fundamental.

And please refrain from commenting "Correct exposure is what you want it to be or how I see it and so on". I understand that. I know when to use 2.8 vs f8 and/or when to slow the shutter speed to get motion to when to increase it to stop motion. I am sorry I have to say this, but I know that there will always be someone that will say that rather then try and help.

Lately what I have been noticing is that I am over relying on flash to get the correct exposure rather than actually metering a tone and trying to get it right without flash.

I understand the Zone system and am reading the book by Ansel Adams "The Negative". I know that I would put totally white with no detail at 2 stops above 18% grey. Totally black with no detail at 2 stops below (though I have heard also that it should be 4 1/3 stops below).

Btw, I want to learn this in terms of spot metering rather than the center weighted or matrix.

The confusion for me starts at...a white towel, for example, can be half in light and half in light shadow...which portion do i put at +2 stops? Logic dictates that I should put the brighter side on +2 and take the shot. But, what if the entire towel was in shadow...that would make that at +2 then. See what I mean?? Where I am confused? No??? well..see the example below:

Below picture is of a 18% grey card in above conditions. The first exposure is the "correct" one since that is what my light meter indicated.

Correct exposure: 1/40 at 2.8 ISO 200



Now below is the one where I spot metered off the darker side and averaged that out: 1/10 at 2.8 ISO 200



And below is where I spot metered off the lighter side and averaged that out: 1/20 at 2.8 ISO 200




As you can see, I get different results and it is the same grey card. So...what gives???

If you were to spot meter..where would you meter from and where would you put the meter at? Average reading? Based on the above exposures...taking from the lighter side, there is one stop difference. From the darker side, there is 2 stop difference. Yet it is 18% grey!!!!!!!

Dazed and confused! Help appreciated. :bow

basflt

i cannot be of any help / advice
but
your camera has 2 meters
one for exposure and one for flash
as long as you use TTL , the flash controls the actual exposure
have you tried he same with manual flash ?

wildviper

Bas,

Thanx. Yeah, I have no issues with flash. It seems that I am perfectly ok with flash and exposure. It is when I am not using flash that is the problem.

basflt

i never seem to get exposure correct either
normally i look at the screen how it is
if ok , i continue , or else i adjust some more
i doubt if it is possible to exposure correct at once

good luck

mstens

In your first shot, were you using average or matrix metering? Nevermind, looking at the exif it's spot. Now, where on the first exposure did you meter?

pathfinder

Viper, these images were jpgs, not Raw? Obviously, if they are Raw, and shot to the right, you can adjust them however you desire.

If your desire is to capture the image of a white towel, your first exposure is seriously under exposed, since it is a dark grey and black.

I think even your second image is under exposed if your goal is to capture a " white" towel. If you have the histograms for these images, I suspect they are all to the left, as opposed to the far right where white tones reside.

A correctly exposed jpg should capture a sixteen step grey scale with each tone distinctly visible.

Reshoot these with your camera in manual mode, and continue lengthening your shutter speed until the white portion of the towel is close the the rightmost limit of your histogram

Buy, beg, or borrow an incident light meter for a different, easier way to meter.

Michael Reichman has written extensively about the correct exposure for digital sensors, and here is his latest rendition, and his earlier Expose to the Right.

I learned a bit about the need for exposure accuracy when I was writing a thread about color balancing tools, like the Expodisc. I shot a lot of stepped grey scales, and if your exposure is off, so are the grey scales, and as a result, any colors you are shooting as well.

wildviper

Ok...sorry..let me clarify few things from my first post.

1. The first shot was exposed using a Sekonic Lightmeter - L-358

2. All the pictures are of a grey card. I used the towel as an example only. (Sorry pathfinder :P )

How do I get the correct exposure in this situation? Spot meter the dark side and average it? Spot meter the lighter side and average it? I am saying "average it" cause it is after all a 18% grey card! Obviously if I do that..the exposure is not correct as per the Pic #1 (which was taken from the incident light meter reading). See the dilemma???

pathfinder

Sekonic L358 is what I had in mind in my post.

Like you, I have found an incident light meter to be the best - indeed, in the movie industry, they use incident meters routinely.

For your second image, if you use a small enough spot on the lighted 18% grey, the exposure should match your first image, shouldn't it?

It makes me think your spot meter is reading part of the shadowed area as well. I think Mike was thinking along this line as well, when he asked where you did your spot metering.

dbd

wildviper wrote: »

...
And please refrain from commenting "Correct exposure is what you want it to be or how I see it and so on". I understand that. I know when to use 2.8 vs f8 and/or when to slow the shutter speed to get motion to when to increase it to stop motion. I am sorry I have to say this, but I know that there will always be someone that will say that rather then try and help.
...

No. you don't understand this and until you do, you can't be helped. It does you no good to put your hands over your ears while saying "Talk to me."

wildviper wrote: »

...
I understand the Zone system and am reading the book by Ansel Adams "The Negative". I know that I would put totally white with no detail at 2 stops above 18% grey. Totally black with no detail at 2 stops below (though I have heard also that it should be 4 1/3 stops below).
...

No, you don't understand the Zone System.

"totally white with no detail" is not something your light meter finds for you. It is where in the range of exposure the Zone System says you (-YOU-) can expose those portions of your image that are brighter than the brightest regions you wish to preserve detail in to avoid losing detail of interest.

"totally black with no detail" is not something your light meter finds for you. It is where in the range of exposure the Zone System says you (-YOU-) can expose those portions of your image that are darker than the darkest regions you wish to preserve detail in to avoid losing detail of interest.

The exposure required for black without detail and white without detail depends on the sensor or film you are using. It is not just determined or measured from the image by your light meter. If the dynamic range of the detail of interest in the scene you are photographing can fit between black without detail and white without detail for the sensor/media you are using, you can proceed to pick an exposure to record the scene. If the dynamic range of interest in your scene exceeds that of your media, you may need strategies like gradient neutral density filters to reduce the dynamic range of the scene to that of the media or multiple image HDR processing to record a greater dynamic range than the media can record in a single exposure.

wildviper wrote: »

...
The confusion for me starts at..
...

Sorry, but your confusion results from seeking direction from your light meter instead of being the photographer and thinking as the photographer. Until you do, your light meter questions are meaningless. Grey cards and light meters do not mechanically decide exposures in the Zone System. Photographers do.

Have you ever considered that the reason "there will always be someone who will say" this is because it is true? People have been trying to help.

Dale B. Dalrymple

mstens

Yep, sorry. I've been on call this week and finally woke up enough to make some coherent sense. I, indeed do suspect that the spot's averaging across your highlighted and shaded section (I think the D300's a 2% spot). This is really one of the problems with a spot meter, especially in calculating an exposure such as the 'white towel' example. Unless you have a VERY fine spot chances are very high that you're going to be averaging across at least 2 zones. Since we're talking about a mixed lighting type situation, to 'match' the incident meter's image I'd also spot off of the lit side.

wildviper

Dale,

No. you don't understand this and until you do, you can't be helped. It does you no good to put your hands over your ears while saying "Talk to me."

Thank you for your post. The reason that I made that comment is because I have seen multiple threads regarding exposures where some smart cookie, rather than help, answers "well it depends"! Of course it depends...I am trying to be very specific here (thus the grey card). I am not trying to get a "creatively correct expsoure" for example. I wanted to get rid of the talk of...well, you should shoot that at 2.8 or f8 or perhaps there is motion and you want to show motion! Or for that matter..."exposures are made by photographers"...well..d'uh..of course they are. But "how"? is my question.

So I am trying to put my hands over my ears for that particular reason. I

And yes, I do understand the Zone system (or trying to) in that "I" pick where the white with no detail is. I understand the photographer makes those decisions. That is why I am asking the question...how do I "see" to be able to make the correct decision!

If you see my above examples of the grey cards...that is exactly my question. How do I expose the darker side of the grey card? Put it one stop under? one stop over? average that? So Dale, you tell me...where would you put the darker grey? +1, -1, 0???

Put it another way:

If I take a pure white towel outside in full sun..I would put that at +2 to render the towel pure white. Now if I take that same towel inside in a dark room...do i still put the towel at +2 even though it has changed its "tone" being the darker room? Just like the grey card above ..in shadow and in light.

Btw, I did spot meter completely from lighter side or darker side. I made sure that I was taking a reading that was not contaminated from the other side.

Qarik

okay let me ask a really dumb question with regard to your setup. are you actually exposing the grey card with your spot meter using the light meter on your camera when you do these shots or are you simply changing the shutter speed,iso, ap based on the sekonic reading? you have to adjust your exposure while the spot is on the dark/light portion to "0" in your camera meter to get the "grey" that you want.

wildviper

Qarik,

For the first shot, I got the reading off the Sekonic Lightmeter and put my camera to those readings. For 2nd and 3rd shots, I averaged the readings with my in camera spot meter aimed far away from contamination onto the grey card (the lighter side and then the darker side).

I am guessing that a grey card is not always 18% grey and is not always average...is it? I think this is where my confusion stems from. I am always trying to put white as white...but sometimes in a dark environment..white may not be white???

mstens

it's ALWAYS 18% grey. It's the reflected light that may change it's value. Consider this. You're outside at night, it's dark. That cards still the same value grey that it is at noon, but your exposure to make that zone 5 will have to change, because of the reflected light. So, if you want your grey card to be zone 5, in the shade, meter on the shaded part. If you want it to be zone 5 in the highlights, do that.

This is where the zone system is valuable. You have the ability to meter any object (even if it's not a grey card) and establish a 'correct' exposure based on the reflected light value of that item. The meter always see's middle grey, so if you're metering a grey card.. you should just go with the meters exposure value (assuming you want the grey-card to be zone 5, it's pushing it in a couple places up there)

Qarik

okay..what you are doing with averaging is not right. 18% grey is 18% grey whether you are in bright light or dim light. Just spot meter and adjust exposure until your in camera meter is reading "0" and you should get "18% grey" exposure..doesn't matter how strong or weak the light is. The 18% grey means it absorbs a certain % of the light that hits it reflects back a certain %...no matter how much light is hitting it.

pathfinder

Grey cards are not uniformly grey. When I was shooting for my thread about color balance tools, one of the things I did was to shoot a Balance Smarter grey reflector ( a copy of Lastolite's color blance tool ) as a jpg, and see how close I could get it to read 128,128,128 in Photoshop. What I found, as you can see in this thread - http://dgrin.com/showthread.php?t=90438 - is that the cards vary across their surface in how light or dark they are. You do not "see" it, but you can certainly "read" the pixels in Photoshop and see that they do vary across the card from center to the corners.

My exposure was chosen with Sunny 16 that day. As you can see, correctly exposed jpgs will display the full 20 steps of the Kodak grey scale.

If one shoots a uniform non-specular mid tone grey surface that is uniformly lit in Av mode, one should see a histogram with a single spike centered in the histogram display in each of the Red, Green and blue channels overlapping.

dbd

wildviper wrote: »

Dale,
...
And yes, I do understand the Zone system (or trying to) in that "I" pick where the white with no detail is. I understand the photographer makes those decisions. That is why I am asking the question...how do I "see" to be able to make the correct decision!

If you see my above examples of the grey cards...that is exactly my question. How do I expose the darker side of the grey card? Put it one stop under? one stop over? average that? So Dale, you tell me...where would you put the darker grey? +1, -1, 0???

I won't make an exposure at all until I had an image concept.

I think you should go back to the "Visualization" Chapter of Adam's "The Negative". In particular note the paragraph beginning, "Our problem, then, includes both concept and procedure." You are still asking about a point of procedure without establishing a concept first. In the Zone System, until you have a concept of an image, you can't decide where to expose a piece of it. If you don't have an image concept, you don't need to take a shot.

If you just want a useful technically correct reproduction of some component, expose as much as possible without damage from clipping. You can put it where you want it later.

If you ever get an image concept to select a towel or grey card exposure for,go back to "The Negative" for the chapter: "Placement of Values on the Exposure Scale" for the procedure part of the process.

Dale B. Dalrymple

wildviper

Qarik wrote: »

okay..what you are doing with averaging is not right. 18% grey is 18% grey whether you are in bright light or dim light. Just spot meter and adjust exposure until your in camera meter is reading "0" and you should get "18% grey" exposure..doesn't matter how strong or weak the light is. The 18% grey means it absorbs a certain % of the light that hits it reflects back a certain %...no matter how much light is hitting it.

Qarik,

I am not sure you and I are talking about the same thing..there is a disconnect somewhere. For example, in my above images, the 'darker' side is 18% grey but so is the lighter side. Its the same card in the same image with two different "luminances". And since I did exactly what you say above, but obviously the exposures are not correct (#2 and #3). #1 is the correct exposure since that was the ONLY one metered using the Sekonic. The Sekonic dome was placed half in shadow and half in light to get that exposure.

Maybe I need to be hit upside the head...but I am confused. :P

pathfinder wrote: »

Grey cards are not uniformly grey.

If one shoots a uniform non-specular mid tone grey surface that is uniformly lit in Av mode, one should see a histogram with a single spike centered in the histogram display in each of the Red, Green and blue channels overlapping.

I agree and know that there is this tiny difference.

dbd wrote: »

I won't make an exposure at all until I had an image concept.

I think you should go back to the "Visualization" Chapter of Adam's "The Negative". In particular note the paragraph beginning, "Our problem, then, includes both concept and procedure." You are still asking about a point of procedure without establishing a concept first. In the Zone System, until you have a concept of an image, you can't decide where to expose a piece of it. If you don't have an image concept, you don't need to take a shot.

If you just want a useful technically correct reproduction of some component, expose as much as possible without damage from clipping. You can put it where you want it later.

If you ever get an image concept to select a towel or grey card exposure for,go back to "The Negative" for the chapter: "Placement of Values on the Exposure Scale" for the procedure part of the process.

Dale B. Dalrymple

Dale, per your suggestion I have begun to re-read the two chapters. I think I know where my confusion is coming from more and more....differences between luminances and 'color'. Since a majority of the time, expsoure is explained on forums as "put white on +2 for white with no detail" and put "black with no detail to -2"....I am just looking at 'color' only. However, as my example above...a grey card can be 'darker' and can be 'lighter'. It really depends on the "amount" of light illuminating it. So it is not about 'color' as it is about the amount of luminance (brightness/darkness) and where to put those.

Right?

By that theory, a caucasian person, for example, in bright sunlight could be +1...but in a darkly lit room..could be -1/3 to get the true tone, mood and luminance no?

Qarik

wilder viper, I am thinkging you are still doing something wrong. You said:

"...the lighter side and averaged that out: 1/20 at 2.8 ISO 200".

What does it means when you say you "averaged"?

wildviper

Qarik wrote: »

wilder viper, I am thinkging you are still doing something wrong. You said:

"...the lighter side and averaged that out: 1/20 at 2.8 ISO 200".

What does it means when you say you "averaged"?

Sorry..."averaged" meaning zeroed it out to get the average exposure of 18%. Middle of the scale.

Qarik

hmmm..then I am stumped. the camera meter should be doing better then that, the 2 greys are close but probly 1/2 stop off. The only thing I can think of is that the spot meter is not as "spot" as it is supposed to be and catching some of other light. If it still bugs you try the expt over again but this time do not light the 2 1/2 differently..just light the whole card as evenly as possible and redo with different strengths. This would isolate whether the in camera meter is an issue.