How to meter properly/Ground glass vs.spotgreenspun.com : LUSENET : Large format photography : One Thread
I have recently purchased the Sekonic L-508 and am considering buying the booster attachment which allows metering directly from the ground glass.Has anyone tried metering in this way? Are there any problems associated with this method.I somewhat of a beginner to LF and would welcome good sound advice. If I cannot accurately(hopefully within 3rd stops)meter directly from the ground glass(due to stray light hitting it etc.)how do you compensate for a polarizing filter whose filter factor can change as you dial in the desired amount of polarization? Thanks in advance for any help or advice.Sincerely Andy
-- Andy Hall (firstname.lastname@example.org), November 18, 2000
I've used a Calculite meter and a fibre optic to take readings off the ground glass. You need to ensure two things. First, calibrate to your ground glass (which is easily done, take a reading off a grey card with your meter and take a reading with the fibre optic through the GG - the difference is what you will need to compensate your readings by. Second, you will need to ensure that no light enters through the back of the camera when you take a reading i.e., the rest of the ground glass, except for the spot you are taking your reading, needs to be blocked off. I've used my dark cloth for this. Re a polarizing filter, you do not adjust exposure according to how much polarization you dial in. The PL needs a constant exposure compensation, usually 2 stops. Good luck. DJ
-- N Dhananjay (email@example.com), November 18, 2000.
I used the Sinar GG metering method for a short time and quickly gave up on it. It was just too, for lack of a better word, complicated. I found that I couldn't be as accurate when choosing my shadow and highlight areas. With a 1° spotmeter, I can really dial in the tonal range. As far as the polarizing filter is concerned, trial and error will be the best teacher. You can also try selecting the amount of polarization, then hold the filter over the lens of a spotmeter while taking the reading.
-- William Levitt (firstname.lastname@example.org), November 18, 2000.
You haven't told us what kind of work you do, or intend to do. Or has that been in another thread I missed?
Metering from the ground glass can be indispensible when shooting macro and you can't get the meter in between the subject and the light source and things are just too constricted "O.K. you move the c- stnad out of the way so I can get in here to meter but put it back so that the flag cuts in right here".
In the three studios I worked in, those kind of conditions didn't come up enough to warrant the expense. In my own work I've always found the lowly Weston Master and Sekonic L398 adequate.
I once watched a group of students set up to shoot 8 X 10 Polaroid of the Robey house in Chicago. Granted, that's not the best example - but it took them a good half hour just to decide on exposure while using a metering back and they weren't using any filtration.
Although B&W does say the Polarizer will affect the exposure by anywhere from 2.3 to 2.8 stops, I have always gotten by with a straight compensation of 2.5
-- Sean yates (email@example.com), November 18, 2000.
I've never quite seen the point of metering the screen, other than with extreme close-ups. It takes for ever and there is a lot of trial and error involved the first time you do it, and every time that you break a screen and have to replace it! I have used the Minolta, not the Sekonic, but the problems of stray light are bound to be the same. The best answer is usually not to use a spot metering, just use an incident metering from the subject back towards the camera, then check with a polaroid. Hope this helps.
-- Garry Edwards (firstname.lastname@example.org), November 18, 2000.
Although I don't meter on the ground-glass, I often meter in _front_ of it using a Horseman Exposure Meter 69, which slips underneath the ground-glass assemblies of my 6x9 cameras (Toyo 23G and Galvin).
I find it useful for close-focus shots since I don't have to make an allowance for bellows extension and also while bracketing exposures, since I can watch the meter needle move while adjusting the aperture in 1/3-stop or 1/2-stop increments.
It also serves as a backup meter in case my spotmeter dies (although as a full-frame averaging type, it's not a direct replacement) and I sometimes find it handier to use than my spotmeter, particularly for closeup shots where there isn't much space between the the lens and the subject.
And, of course, it lets me easily determine how much compensation is needed when using various filters, including a polarizer.
-- Jeffrey Goggin (email@example.com), November 18, 2000.
Sheesh you guys make it too hard on yourselves. james
-- lumberjack (firstname.lastname@example.org), November 18, 2000.
Andy, unless you do extreme close ups or use a ton of filters don't even consider it...and if you do buy it, be sure the place you buy it from offers returns, it is a special order item. I bought one and returned it, it is very poor. The meter was off by 3 stops, and it was not predictably off, it varried from area to areas based on the amount of light... This is a very tricky thing to accomplish, and these add on type devices are an attempt to match the effectiveness of the dedicated units costing 10x more... It's good in theory, but the products don't live up to their billing in practice!
-- Bill Glickman (email@example.com), November 18, 2000.
Andy I've been using the L508 for some time now and I am very pleased with it. I wouldn't bother with the booster attachment for all the reasons mentioned above. One of the reasons I chose this meter was because it simplifies the metering procedure, especially when employing the zone method. Using and calibrating the booster introduces unecessary complications.The L508 has 2 ISO buttons so it is easy to dial in filter compensation and recall it at a touch of a button. With partial polarizing you would do just as well by exposing both sides of the film holder applying bracketing to the second sheet. Also I find it is easier to locate and measure shadow and highlight areas through the meter eyepiece rather than through a dimmer GG. Save your money for film (LF is a steep learning curve!!!!!) Regards Paul
-- paul owen (firstname.lastname@example.org), November 19, 2000.
I recently saw a photo of the setup which a local food photographer uses. It looked like he used one of those fancy and very expensive meter probes on the lens side of the ground glass. But then, he does lots of work at 1:1. Of course most of his setups are done with stand-ins, and he shoots Polaroids after exposing the film so the real exposures are with the food at its freshest.
Regarding polarizers - I've used a constant factor of 2.5 with success. For what it's worth, Ansel Adams recommends not changing the exposure as a function of degree of polarization as a general rule. The exception being where the effect of polarization uncovers detail which you then might want to account for in determining your exposure.
-- Larry Huppert (Larry.Huppert@mail.com), November 19, 2000.
I have been shooting large format architecture (exteriors and interiors) in the Atlanta area for just under 20 years and the best thing I ever did was decide (about 12 years ago) to exclusively use a 1 degree spotmeter and when taking my film to the lab uttering these two very scary words - "Process Normal".
I once shot an interiors job using incident readings (14 years ago) and I still am haunted by the poor outcome of that assignment. The only way to meter is with a spotmeter. I don't care how much light is falling on a navy blue upholstered chair. I only want to know how much light is bouncing OFF of that chair. Same goes for walls, artwork, carpet... you name it.
I have always had good success making a 2 stop allowance for may polarizers, but different brands so vary in density.
-- Jim Roof (email@example.com), July 22, 2001.
I will give another vote to the Calculite with the probe. It is easy to use and give readings quickly. But I got tired of working with the meter under a dark cloth & mainly use a spot meter now. More because I like watching the image area than because the ground glass metering did not work or was difficult. Only a matter of personal preference. As for the Calculite meter, it is still in my bag & used as a backup. Small, lightweight & accurate and it meters in light lower than most.
-- Dan Smith (firstname.lastname@example.org), July 22, 2001.