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Questions re: Photo Vision Target
Old 08-25-2007, 03:05 PM   #1 (permalink)
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I have two shoots coming up tomorrow and I want to get some use out of the Photo Vision target I bought but I do not like to go into anything blind so I thought I would do a little experimenting with it in my garden.

Using a light meter of known accuracy I took a couple of shots at F5.6 @ 1/400 sec and got a good and balanced histogram and I like the way it looks on my monitor in Photoshop.

I then set up the target in the same location and the first image I took totally blew out the highlights. I only had two spikes on my Histogram. I gradually increased the shutter speed until I was at 1/1000 sec and then I got a good Histogram with three evenly distributed spikes on the Histogram.

As of now with this Photo Vision target I am pretty much taking everything on faith but eventually I would like to get to the point where I understand the method behind the system because then and only then will I be a better photographer.

Can anyone help me out with an explanation for this seeming discrepancy? Thanks.
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 04:44 PM   #2 (permalink)
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Quote:
Originally Posted by PhotoDave1 View Post
I have two shoots coming up tomorrow and I want to get some use out of the Photo Vision target I bought but I do not like to go into anything blind so I thought I would do a little experimenting with it in my garden.

Using a light meter of known accuracy I took a couple of shots at F5.6 @ 1/400 sec and got a good and balanced histogram and I like the way it looks on my monitor in Photoshop.

I then set up the target in the same location and the first image I took totally blew out the highlights. I only had two spikes on my Histogram. I gradually increased the shutter speed until I was at 1/1000 sec and then I got a good Histogram with three evenly distributed spikes on the Histogram.

As of now with this Photo Vision target I am pretty much taking everything on faith but eventually I would like to get to the point where I understand the method behind the system because then and only then will I be a better photographer.

Can anyone help me out with an explanation for this seeming discrepancy? Thanks.
The light meter is calibrated to give you proper exposure of a gray card. What you are doing with the target is checking that shadows, midtones and highlights are all going to be properly exposed. If you shot just a gray card in this light, then the proper exposure would normally show one single spike in the center of the histogram. You would then adjust the exposure up or down depending on your subject (whether it was light or dark). But since, with the target, you are working with three spikes, you are actually testing the whole range of the scene. Suppose you were shooting a model wearing a white dress. If you used the gray card exposure, you very well might blow all the highlights in the white dress if you followed the meter blindly. Naturally with a white dress, you have to lower the amount of light that falls on it to keep in from blowing out. And that is exactly what the target showed you, correct?
But even with the target, you still may need to adjust the exposure depending on the scene. Take that same model, but wearing a jet black dress. Now what do you want. You may need more light on the dress since black absorbs 90% of the light, so you would change the exposure. But keep in mind you still want the model properly exposed (face for example), so there is often a compromise, or you light the dress separately.
As a general rule, when using the target, you'll want to try to have the three spikes as far right as possible without blowing the highlights. This automatically gives you more detail in the shadows due to the linear nature of digital.

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Re: Questions re: Photo Vision Target 


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Re: Questions re: Photo Vision Target
Old 08-25-2007, 04:49 PM   #3 (permalink)
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Were you shooting with a zoom? The nature of zoom lenses -- not all zoom lenses but most -- is that the effective aperture is affected by the focal length. Zoom in (longer) and your effective aperture is higher, zoom out (wider) and your aperture is lower - hence the difference in exposure. The difference is not huge but might be enough to have made the difference if you shot the target with a zoomed out focal length and the meter shot at a zoomed in focal length. Your adjusted exposure was a little over a stop so maybe it would fall within this f/stop range. Sounds like the only explanation for the discrepancy without knowing more by being there.

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Re: Questions re: Photo Vision Target
Old 08-25-2007, 05:37 PM   #4 (permalink)
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I grew up with Film and I guess old habits die hard. I still have a set of working Asahi Pentax H2 cameras that work and I still use and also a set of Leica M3 rangefinder cameras also that still work and I still use.

It used to be that photography was about exposing for the Film and now photography has evolved to the point where everything has become about the computer and the camera is only a small bit player and I am not sure at all that I like this but it is what it is. I also think that computers have made photography a lot more complicated and complex than it really needs to be but it is what it is and time certainly marches on and a person either has to march with it or get trampled.

This is in no way intended as a critism or a slap in the face to the many professionals and those who have helped me along the way but I'm an old dog and this dog misses the old days. Nuff said!

Quote:
Originally Posted by R_Fredrick_Smith View Post
The light meter is calibrated to give you proper exposure of a gray card. What you are doing with the target is checking that shadows, midtones and highlights are all going to be properly exposed. If you shot just a gray card in this light, then the proper exposure would normally show one single spike in the center of the histogram. You would then adjust the exposure up or down depending on your subject (whether it was light or dark). But since, with the target, you are working with three spikes, you are actually testing the whole range of the scene. Suppose you were shooting a model wearing a white dress. If you used the gray card exposure, you very well might blow all the highlights in the white dress if you followed the meter blindly. Naturally with a white dress, you have to lower the amount of light that falls on it to keep in from blowing out. And that is exactly what the target showed you, correct?
But even with the target, you still may need to adjust the exposure depending on the scene. Take that same model, but wearing a jet black dress. Now what do you want. You may need more light on the dress since black absorbs 90% of the light, so you would change the exposure. But keep in mind you still want the model properly exposed (face for example), so there is often a compromise, or you light the dress separately.
As a general rule, when using the target, you'll want to try to have the three spikes as far right as possible without blowing the highlights. This automatically gives you more detail in the shadows due to the linear nature of digital.

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Re: Questions re: Photo Vision Target 


Cheers,
rfs
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 06:01 PM   #5 (permalink)
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It used to be that photography was about exposing for the Film and now photography has evolved to the point where everything has become about the computer and the camera is only a small bit player
It is still about exposing for the film. Except that now, in general, the film has a bit less dynamic range and latitude, the response curve is linear, and instead of a graceful curve at the shoulder and toe, you slam straight into a wall. Also, you can't change your film without buying a new camera.
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 06:04 PM   #6 (permalink)
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Quote:
Originally Posted by PhotoDave1 View Post
I grew up with Film and I guess old habits die hard. I still have a set of working Asahi Pentax H2 cameras that work and I still use and also a set of Leica M3 rangefinder cameras also that still work and I still use.

It used to be that photography was about exposing for the Film and now photography has evolved to the point where everything has become about the computer and the camera is only a small bit player and I am not sure at all that I like this but it is what it is. I also think that computers have made photography a lot more complicated and complex than it really needs to be but it is what it is and time certainly marches on and a person either has to march with it or get trampled.

This is in no way intended as a criticism or a slap in the face to the many professionals and those who have helped me along the way but I'm an old dog and this dog misses the old days. Nuff said!
I think it was just as complicated then. Each film had a different way you worked with it. If you shot slide, you had to be more exact in your metering, but had more leaway with negative film. You often adjusted your exposure compensation based on the type of film you were using, or if you were pushing or pulling it, or if you were using the Zone system, etc. When you used filters, you had to adjust your exposure depending on the type of filter. You had to allow for reciprocity failure in certain scenes.

But the same rules of photography still apply. You have to get the right exposure for the scene you are shooting. In the old days you changed exposure values based on what you planned to do in the darkroom and now you change exposure values based on what you plan to do in Photoshop.

I try to treat digital as a new type of film. What are some of the comparisons we can make if we use this as a metaphor. Well, latitude is one. Digital is more like slide film. You have to be more precise in your exposure values. I always tried to get as close to the exactly proper exposure for a scene as I could when shooting slides film because I new I had only about a 1/3rd stop leaway. That is just the way digital seems to behave. Some films did a better job of capturing shadow detail. Some worse. Digital can be worse since it is a linear process. But since we know it is linear we adjust our exposures to move the shadow details further to the right on the histogram. With film, we adjusted in the developing of the film or chose a film that was better on the shadows. An on it goes.

Now, back to your original post. Another consideration is how you use your handheld light meter. If you use it in reflective mode, then that would not correspond at all to the target usage. The target behaves more like an incident reading. But in that regard, if you metered with an incident bulb, then that bulb is half of a sphere and is collecting a good deal of light that the flat surface of the target would not collect. I like to think of the target as taking three reflective spot light meter readings and then averaging them in some way. One reading of the shadows, one of midtones and one of highlights. This corresponds to the three spikes of the target. And this also corresponds to a similar process when using the old zone system. You use the histogram today to determine where your highlights or shadows will be, or in other words what zone are you forcing them into by your exposure choices.

But when all is said or done, you will need to experiment with the target and calibrate it to the way you use Photoshop, and then you'll get to the point where you are very comfortable with using it. You need to be sure that the target's histogram looks correct when viewed in Photoshop. The histogram in PS might not match the histogram on the camera, in other words. The other think to be really sure of is that you fill the whole viewfinder with the target. If you don't, then you're not getting an accurate measure of the three spikes. It is also important to put the white side of the target on the side where the light is brightest (where the main light is).

Cheers,
rfs
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 06:24 PM   #7 (permalink)
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Originally Posted by RobArtLyn View Post
It is still about exposing for the film. Except that now, in general, the film has a bit less dynamic range and latitude, the response curve is linear, and instead of a graceful curve at the shoulder and toe, you slam straight into a wall. Also, you can't change your film without buying a new camera.
Actually you may not have to buy a new camera. One can just change the contrast, saturation, sharpness, white balance, and other camera parameters to simulate whatever "film" one wants. A person can do the same thing in RAW. A plethora of plug-ins are available that let you select a simulation of whatever "old" film type is wanted. The biggest difference for me between film and digital is just having to always take more care to be right on, on the exposures (just like you had to do with slide film).
Cheers,
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 06:46 PM   #8 (permalink)
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Several people have asked me this and I keep forgetting to answer. In 99% of cases I use my meter in Incident mode. If I was going to use my meter in Reflected mode I would simply toss my meter and use the camera's meter.

You mention taking three reflective readings and then averaging them. I know some upper end meters (including the Minolta Autometer 4F which I owned briefly) can do this but I never took the time to figure out how to make it work. I would imagine the algorithm to make this work must be quite sophisticated.

Thanks for the lighting and metering lesson. At least I am beginning to understand a little better what I am supposed to be doing.



Now, back to your original post. Another consideration is how you use your handheld light meter. If you use it in reflective mode, then that would not correspond at all to the target usage. The target behaves more like an incident reading. But in that regard, if you metered with an incident bulb, then that bulb is half of a sphere and is collecting a good deal of light that the flat surface of the target would not collect. I like to think of the target as taking three reflective spot light meter readings and then averaging them in some way. One reading of the shadows, one of midtones and one of highlights. This corresponds to the three spikes of the target. And this also corresponds to a similar process when using the old zone system. You use the histogram today to determine where your highlights or shadows will be, or in other words what zone are you forcing them into by your exposure choices.
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Re: Questions re: Photo Vision Target
Old 08-25-2007, 07:20 PM   #9 (permalink)
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Several people have asked me this and I keep forgetting to answer. In 99% of cases I use my meter in Incident mode. If I was going to use my meter in Reflected mode I would simply toss my meter and use the camera's meter.
Using reflective readings in the spot mode is a very important method of metering. In the Zone System, that is exactly what you do, because you want to know the value of the light for the zone you meter on. Take the example of the model in a black dress. An incident reading does not give you the proper exposure for shot if the black dress is the critical item in the scene. The incident meter shows how much light is falling on the scene, but does not show how much of the light is being reflected. Still most photographers, especially in the studio, do mostly incident readings, and then then compensate based on the lightness or darkness of key elements in the scene. When I use reflective readings (and by the way I have the Minolta IV and have been using it for over 20 years), I often use its averaging capability. So you don't have to do any math, you can let the meter do it for you. Most all of the newer meters have this ability.

Anymore, though, with the advent of the histogram, I pretty much just compensate by eye, and hardly even use the meter any more. The target is used to zero in on the optimum exposure for the whole scene, and then I adjust as needed for the elements in the scene. I do use the meter to establish lighting ratios (incident mode).

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Re: Questions re: Photo Vision Target
Old 08-25-2007, 08:57 PM   #10 (permalink)
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Quote:
Originally Posted by R_Fredrick_Smith View Post
Using reflective readings in the spot mode is a very important method of metering. In the Zone System, that is exactly what you do, because you want to know the value of the light for the zone you meter on. Take the example of the model in a black dress. An incident reading does not give you the proper exposure for shot if the black dress is the critical item in the scene. The incident meter shows how much light is falling on the scene, but does not show how much of the light is being reflected. Still most photographers, especially in the studio, do mostly incident readings, and then then compensate based on the lightness or darkness of key elements in the scene. When I use reflective readings (and by the way I have the Minolta IV and have been using it for over 20 years), I often use its averaging capability. So you don't have to do any math, you can let the meter do it for you. Most all of the newer meters have this ability.

Cheers,
rfs
Hi Roger,

I thought you wanted to use incident for a black dress. Reflective would give you the wrong reading, because it is not 18% grey. My understanding is that a reflective reading would try to make the black dress 18% gray. An incident reading, on the other hand, doesn't care about whether you are shooting a white bride's dress or a black dress.

You can see a more detailed description of that here at Sekonic's site:

http://www.sekonic.com/classroom/classroom_2.asp

Look at the first example with the white, gray, and black plates with incident metering. And then look at similar examples below with reflective metering.

All that said, I recently photographed a model in a black dress and I overexposed. I did something wrong somewhere.

If I have a misunderstanding, please correct me.

Best regards,
Kevin
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