Metering for highlights? (Sinar Booster 1)

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Dazzer123

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Hi folks,

I'm making my first attempt at metering for highlights with my Sinar Booster 1.

Problem seems to be that the highlights are too small in area to cover enough of the Booster 1 sensor to get a sensible reading.

So i was a-thinking, maybe i need to get some larger, metallic object (my highlights are coming from chrome / metal in the scene) to temporarily place in my scene, so i can create a bigger highlight area to meter off.

So my question is (and i'd be especially interested to hear from old studio hands from back in the day), does this sound like a good idea, and if so, what would be a good object? A flat sheet or something rounder?

The objects in the scene (mostly knobs) are convex, so i don't think they're focusing the light more than a flat object would.

And any other tips or tricks from back in the day to deal with this?

Thanks!
 
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I wouldn't normally meter for specular highlights, even with digital, unless maybe if I'm after a low key image where the reflections are the subject. I haven't don't that. But I don't think all specular highlights are the same, as you note their brightness depends i.a. on the shape, and they aren't homogenous in themselves either. So what to use for a larger stand-in? I think this is probably easier to do by incident metering and experience-based fudge factors if precise exposure for the highlights is critical.
 

wiltw

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Biggest issue is getting your reflective target at the correct angle to mimic your actual highlight area for metering purposes. It sounds like you are shooting 'products' and the lighting is under control of the photographer, so can set the ratio of the sources to control the dynamic range of the subject to fall within a narrower range, so once lighting is set you only need to set for Exposure (mid-tone)
 
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wiltw

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Should be do-able? Just angle it till it looks equally bright on the GG?!

Are you talking about 'highlights with detail' or the 'blown out highlight areas' which can be reflections of light sources in shiny bright surfaces?
The former is certainly not that difficult, but for the latter you have to take a planar mirrored surface to shine the reflection to lens position, not that easy!
 

_T_

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If you took a picture of the subject with your cell phone and posted it here we would be better able to help you understand what you need to do to meter the scene.
 
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Dazzer123

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I guess i'm talking about the brightest highlights that aren't completely blown out.

I'm not looking for a solution for a specific scene, more interested in tricks and techniques that would have been used back in the day in studio photography, because these are not well documented!
 

Hassasin

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Emulating reflection quality with temporary piece it would have to have exactly same reflective quality, easier to say than do. Why not change the lens to longer focal for metering at same aperture to get larger target, then switch back for the shot ?
 

koraks

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I generally just take a reading with an incident meter in various places and then base exposure on that. Let specular highlights fall where they may. The quality of the light (more collimated vs. more diffused) will determine the nature of the reflections and how harsh they'll be.

It sounds like you're running into many challenges with your Sinar Booster setup. I'd really consider getting a good grip on more simple metering first. Learn to walk before trying to run, and all that. I know you said somewhere that you believe that the Booster is the simplest way to meter, but I have to disagree. It's a system that adds a lot of complexity to your metering setup. I'd start by reducing this complexity, which also extends to the scene you're shooting. I know the example you're talking about here; it's the tape deck, right? Why not start with the same object and light it with a single diffuse fill light and perhaps one or two accent lights instead of your setup with the colored strips and whatnot.

Maybe practice on B&W negative film, too, instead of color slide film, to make experimentation a little more affordable. If you practice with e.g. Fomapan 200 sheets you'll have 10 times the learning opportunity at the cost of 1 sheet of slide film - if not more. This is one of those things in life where you need to practice lots in order to get it. Theory has a place in it, too, but it augments practical experience. It's not a substitute for it.

Simplify first, then add layers of complexity as you learn the ropes.

I'm not looking for a solution for a specific scene, more interested in tricks and techniques that would have been used back in the day in studio photography, because these are not well documented!

They're not well documented because the tricks & techniques arose from a basic level of competence. If you've got that, you can trick your way out of just about any situation, and you'll also realize by that time it's really not about the tricks, and that the tricks are just practical solutions people arrive at by applying theory and experience to a particular situation. You'll also understand that each photographer will approach the problem differently, which ultimately also accounts in part for their distinctive style. Conversely, you can read about tricks all day long without learning much from it, because they'll only make sense on the basis of a solid understanding of the basics. That's one more reason I'd start there.

I know, it doesn't sound very exciting, and perhaps even tedious, but I'd really start with the boring stuff like "photograph a white egg on a white dish with a single light source" etc. By doing this, you may also find that it's not as tedious as it sounds, because it's actually pretty challenging to do this well, and that photography is also a craft that you don't acquire by reading a book, manual or asking for tricks & techniques.
 

foc

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This is one of those things in life where you need to practice lots in order to get it. Theory has a place in it, too, but it augments practical experience. It's not a substitute for it.

You'll also understand that each photographer will approach the problem differently, which ultimately also accounts in part for their distinctive style. Conversely, you can read about tricks all day long without learning much from it, because they'll only make sense on the basis of a solid understanding of the basics. That's one more reason I'd start there

but I'd really start with the boring stuff like "photograph a white egg on a white dish with a single light source" etc. By doing this, you may also find that it's not as tedious as it sounds, because it's actually pretty challenging to do this well,

Excellent sound advice.

Studio lighting and exposure can range from very simple to very complex.


If you took a picture of the subject with your cell phone and posted it here we would be better able to help you understand what you need to do to meter the scene.

This would help a lot.

Meanwhile, have a look here, go through the various menus and it might help to give you an understanding of studio lighting.

http://www.tabletopstudio.com/jewelry_photography.html
 

Hassasin

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Hard to go studio without investing in the Light Science & Magic. Best text on the subject and far more relevant than it may seem at first for this discussion. Understanding light and all its tangibles goes a long way in understanding trickery of exposure.
 

Bill Burk

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Biggest issue is getting your reflective target at the correct angle to mimic your actual highlight area for metering purposes. It sounds like you are shooting 'products' and the lighting is under control of the photographer, so can set the ratio of the sources to control the dynamic range of the subject to fall within a narrower range, so once lighting is set you only need to set for Exposure (mid-tone)
Great to have your opinion on this.

wiltw has shared some interesting studies of the reflectance of gray cards held at different angles.

So I would listen to him on this one.
 

MattKing

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Hard to go studio without investing in the Light Science & Magic. Best text on the subject and far more relevant than it may seem at first for this discussion. Understanding light and all its tangibles goes a long way in understanding trickery of exposure.

+1
 

ic-racer

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Not sure how you will be "metering for highlights."
I presume you are using reversal film. Do you know the dynamic range of the film and how the meter is calibrated? You probably need to run some tests of the equipment to see if the highlight is anywhere from two to four stops from the meter's calibration point.
 

wiltw

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Great to have your opinion on this.

wiltw has shared some interesting studies of the reflectance of gray cards held at different angles.

So I would listen to him on this one.

Thanks for rememberting that post, Bill! I can't seem to find the original thread, so instead I will re-post the images from that test and from another test..

This photo was taken with fixed exposure setting on camera, and what I did was alter the anble of a not-shiny surfaced gray card, relative to sun position, with camera set on tripod. And I also changed the angle of the camera relative to sun position. It illustrates the range of brightess only with rather moderate angle changes!

Evaluative-1.jpg


And here is the other test, remembered by Bill, with the camera at a fixed angle to the sun, but the gray card moved around to various angles, to represent how the gray card density can be altered simply with angle of the card being changed, sometimes rather significantly.
cardreflectance_zpsgopvvxjl.jpg

If you were manipulating at shiny surface (like a mirror) the angle could have an even greater effect when it reflects an imange of the light/sun back to the lens (vs. when it doesn't)!
 
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Hassasin

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Thanks for rememberting that post, Bill! I can't seem to find the original thread, so instead I will re-post the images from that test.

This photo was taken with fixed exposure setting on camera, and the ONLY thing that I did was alter the anble of a not-shiny surfaced gray card, relative to sun position, with camera set on tripod. It illustrates the range of brightess only with rather moderate angle changes!

Evaluative-1.jpg
I'm not sure what this test proves. If anything that it is of a hand held card with surely varied yet unknown angle to lens axis on every one of them, varied in all directions, yet background (strangely different in almost all of them) looking exposed quite similarly. One could conclude ... why bother even using a grey card. And generally there is hardly any in-scene material carrying similar to grey card qualities.

EV of reflected light will differ depending on how it bounces off a specific material (its flatness, how much of total reflected light becomes scattered vs. direct, and how all these angles line up with lens axis), absorbing qualities of that material and several other factors.

Metering reliability goes further when incident vs. reflected is considered (both having pros & cons), and in all this sticking a piece of "foreign" matter in a scene can often lead to wrong conclusions.

The only correct placement of a grey card is centred dead on and perpendicular to lens axis. Because the only sure value from using one is in this one and only setting.

Grey card is fine for testing (ZS or not) routines, otherwise quickly becoming a nuisance device, often complicating metering rather than augmenting it. Of course if one intends to photograph a grey card for the next exhibit, then it is a great abstract.

My take: measure what you've got in the scene, use spot meter for better precision, learn how to interpret those readings, consider incident as possibly better solution to desired outcome, and by all means, if highlights are the key area of concern, measure for them and compensate as needed.
 

wiltw

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I'm not sure what this test proves.

It shows that if one is trying to use a panel reflector as a surrogate for some tiny point on a reflective curve, the amount of reflectivity varies due to the angle that the panel happens to be, relative to the position of the actual light source falling on the subject....otherwise the 18% gray card would have a single unitorm reflectivity regardless of the angle at it was positioned.
Similarly, if I held a mirror reflecting the sun to your eyes, at ONE angle, it will dazzle you and make you squint...to unless I hold it at that precise angle to meter with the Sinar Booster, the Sinar will not see the highlight at its brightest.

As you yourself have stated, "The only correct placement of a grey card is centred dead on and perpendicular to lens axis. Because the only sure value from using one is in this one and only setting." Kodak had pretty specific instructions about the angle of the gray card, too...my test proved that other angles could make a significant difference in a reading off a gray card.
IOW, regardless if it is gray card or mirrored surface, ANGLE MATTERS.
 
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Thanks for rememberting that post, Bill! I can't seem to find the original thread, so instead I will re-post the images from that test and from another test..

This photo was taken with fixed exposure setting on camera, and what I did was alter the anble of a not-shiny surfaced gray card, relative to sun position, with camera set on tripod. And I also changed the angle of the camera relative to sun position. It illustrates the range of brightess only with rather moderate angle changes!

Evaluative-1.jpg


And here is the other test, remembered by Bill, with the camera at a fixed angle to the sun, but the gray card moved around to various angles, to represent how the gray card density can be altered simply with angle of the card being changed, sometimes rather significantly.
cardreflectance_zpsgopvvxjl.jpg

If you were manipulating at shiny surface (like a mirror) the angle could have an even greater effect when it reflects an imange of the light/sun back to the lens (vs. when it doesn't)!

S0 how do you use this card accurately?
 
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It shows that if one is trying to use a panel reflector as a surrogate for some tiny point on a reflective curve, the amount of reflectivity varies due to the angle that the panel happens to be, relative to the position of the actual light source falling on the subject....otherwise the 18% gray card would have a single unitorm reflectivity regardless of the angle at it was positioned.
Similarly, if I held a mirror reflecting the sun to your eyes, at ONE angle, it will dazzle you and make you squint...to unless I hold it at that precise angle to meter with the Sinar Booster, the Sinar will not see the highlight at its brightest.

As you yourself have stated, "The only correct placement of a grey card is centred dead on and perpendicular to lens axis. Because the only sure value from using one is in this one and only setting." Kodak had pretty specific instructions about the angle of the gray card, too...my test proved that other angles could make a significant difference in a reading off a gray card.
IOW, regardless if it is gray card or mirrored surface, ANGLE MATTERS.

I posit the test would have been more revealing if we actually got the readings from the different angles.
 

wiltw

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S0 how do you use this card accurately?

I cite what Kodak published on the topic (publication date 2007 on supplied instructions):

  • In artifical light: "Aim the surface of the gray card towards a point one third of the compound angle between your camera and the main light." (see note)
  • In daylight: orient the gray card in the same way as recommded for artificial light using the sun as the main light.
  • In shade: under overcast skies, or in backlight situations, use the brightest area in front of the subject, usually the sky as the main light.

note: The illustration shows the 'compound angle' to be the angle of [the subject at the vertex, formed between the light source and the camera lens axis], and one-third of that angle is measured starting from lens axis side of the angle, toward the sun side.
 

wiltw

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I posit the test would have been more revealing if we actually got the readings from the different angles.

I will try to find the original RAW file, and then alter Exposure to achieve same brightness reading with Eyedropper tool, and annotate with the exposure offsets required. Stay tuned....

Here is test series annotated with the exposure offsets...the second frame was exposed per the meter, and its brightness readings per the Eyedropper tool are 49/49/49. All other frames were individually adjusted using Lightroom's Exposure adjustment, typing in specific values even in the hundredths of EV to achieve 49/49/49 end result. Each frame is annotated so that the underexposure (negative value) or overexposure (positive value) is quanltified.

Graycard_angle.jpg


So one can see that the angle of the gray card, when not held at 'the right angle' could result in a range of error of -1.75EV to almost +1.5EV ...and this test, seen in the capture of the sky on that day, was done on an overcast day, where the sun position is neutralized somewhat by the 'large overhead source' created by the overcast.
 
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wiltw

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Since the prior test was under an overcast sky, I decided to replicate the test under a early winter sunny sky (about 11am), at about Latitude 38.
Facing camera (at my 12 o'clock), the sun was about my 2 o'clock, so the compound angle was not really wide. I first held the card about perpendicular to the ground facing my 11 o'clock and swung it thru an arc toward sun position at 2 o'clock, then I angled the card upward slightly (about 15-20 degree tilt...note tilt change from frame 5 to frame 6) and swung it back thru the arc to my 11 o'clock. I would estimate that the arc that the card travelled was about 90 degrees wide. It this time of day, the sun was about 45 degrees higher than horizon. The card is an official Kodak gray card with non-lustrous surface texture.

graycard_angle_sun.jpg


One can see that reflected light from the card varied in brightness about 5EV (from about -1.85EV to +3.2EV), and even at very small angle changes one could get a range of brightnesses within a 1EV range. In comparison, under overcast sky the brightness range was about 3.2EV
...as I stated, the sun position was neutralized somewhat under the 'large overhead source' even with a rather extreme tilt of the card (compared to sun test tilt angle).
 
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feanolas

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Back to the OP question, I imagine specular light is close to the intensity of the light source, so measure the light source directly and place it in zone X and you should be good.
 
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