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Light meter question

Discussion in 'Exposure Discussion' started by Stelex, Apr 12, 2017.

  1. OP
    OP
    Stelex

    Stelex Member

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    Ouch, that's expensive. I'd be more interested in something of a Canon 700D level, just with film, and also being more manual. The F6 looks nice but apart from the cost, it's too automated for what I'd be looking for. A brand new AE-1 or A-1 would be awesome. I know, I know ... 20-30 years too late :smile:
     
  2. BMbikerider

    BMbikerider Member

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    You can carry a seperate meter (already mentioned) You can develop your film to suit the exposure (already briefly mentioned) Or you can use the palm of your hand to meter from and add one extra stop. so if the exposure of 1/250 a second at F8 either change theshutter to 1/500 or the aperture to F11. It works every time with almost every correctly functioning camera I know.

    As for the variations of readings between different cameras on page one of this thread, don't forget some of these cameras are around 30-40 years old and who is to say they are all correcly adjusted. Also if each camera has a different lens the lenses may have different light transmission values. You must use a prime lens as well Zooms can be very difficult to evaluate.

    (Yes the F6 metering is almost damn well foolproof and I use mine as the benchmark when I check my other cameras.)
     
  3. Diapositivo

    Diapositivo Subscriber

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    Regarding the home tent comparison, I would repeat that with the lenses at f/8. At full aperture there is some vignetting and if the cameras have different metering patterns that will weigh on the exposure. With f/8 or f/11 or something like that you certainly eliminate the variability that vignetting introduces in your test.

    Also, you should close the entrance of light into the camera from the viewfinder. That can influence the reading in a different way in the different cameras.

    Finally, I would do a test in full light. In the low light range different light meters might have different precision.

    When all this is corrected, I think you should have 1/3, or 1/2 of EV of difference between different cameras with the same lens.

    If you don't, you might either "memorize" it, just keep in mind the different behaviour of the light meters, or re-calibrate some cameras in such a way as to have the same behaviour, if that helps you working more comfortably.

    The choice of exposure can be subjective, but the measurement of light should be objective and "correct". Based on that, you make subjective choices regarding the desired exposure of your frame.

    I am a user/proponent of external light meters, both incident light and spot reflected light. When you get used to that, and correctly grasp their use and the principles of exposure, you will see that you will use internal light metering only on certain occasions.

    The problem of the overexposure of the shots - if present - is separate from the mismatching of the lightmeters: old second-hand cameras deserve cleaning, lubrication and shutter adjustement (and maybe light-meter adjustement) otherwise you are also dealing with different behaviours of shutters.

    When using external light meters you will use your camera in manual mode and therefore it is important (especially if using slide film) that your shutter speeds (and your lens apertures) are correct, or correctly calibrated.

    Generally speaking, when using black and white film you have a certain comfortable room for exposure "mistakes" and, from what I gather on APUG, you will get to your final desired result in any case. It's when using slides (as I do, I only use slides basically) that light metering becomes important, or even very important, if you want to exploit the entire density range of the material.
     
    Last edited: Apr 17, 2017
  4. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    been with a video analyzer like Kodak's VCNA. And since VCNAs used to cost as much as a small house, I'm guessing you didn't have one. I may be "dissing" smaller pro labs, but back in the day a VCNA was the big productivity tool, eliminating one or two color balance tests. It became a completely different world when a main mini-computer took over control of printer exposure and color balance, according to the analyzer data for each neg. I guess I'm reminiscing too much.[/QUOTE]

    Back in the day, Caltrans had a Kodak Photo Video Analyzer Computer (PVAC). I might have forgotten the exact name. But it's a desk sized analyzer with a monitor that simulated a calibrated RA process. There were 3 color wheels and a density wheel on the console if I remember correctly. You balance out the video image, read the numbers off the monitor than transferred the numbers to the special color head. I never came close when the print came out of the processor. Again, it's mind numbing work.
     
  5. Mr Bill

    Mr Bill Member

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    Hi, it's kind of unusual to run into someone who has actually used one, and btw you're close enough on the name; everyone just called them PVACs. The VCNA was the all analog predecessor, functionally the same thing. In our very large lab we had four of them; due to the high cost the operator's seat was always filled, rotating alternates in during lunch and break periods. We only analyzed 2 or 3 negs near the front of a long roll, then ran those through a printer for color balance tests. The VCNAs/PVACs were pretty reliable to get you within about 5 cc of the final color, not good enough for us to go to print, but certainly eliminating one or two color color tests, which is what paid for the machines.

    I don't know why they weren't working out for you, but there was a lot of setup that had to be just so. You first had to manually color-match prints from each neg in the slope set, then visually match them on the PVAC. This established the PVAC-to-print relationship as well as the printer slope. Each film type needed its own slope negs, as well as Kodak-supplied film matrices loaded into the system. Everything after this relied on both the printers and paper processors staying nearly dead-on to the conditions where setup was done. So it's sort of a "house of cards" thing; if you can't maintain all the little details the whole thing comes apart.

    I often described our operation as a "picture factory," where the work is essentially a sort of production line thing. Regarding "mind numbing," I used to occasionally asked some of the regular "production" people if it didn't drive them crazy, but mostly they said no, they could do the work without thinking, so they could be thinking about family matters or whatever. So a lot of it seems to be how you look at it.
     
  6. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    I guess I'm just not too smart :wink: But I think most of direct analog printing from negs are gone now. The majority of the RA printing I'm guessing most are scans. The image is corrected digitally then printed with this device.

    http://camerabazar.blogspot.com/2010/10/fujifilm-digital-minilab-frontier-390.html

    Maintaining the RA processor is still the same.
     
  7. Robin Guymer

    Robin Guymer Subscriber

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    In 1974 an international standard was made that all light meters for cameras would be the same, ISO:2720. I became interested in the same question when I found my custom built (Sony Nex) digital back has correctly exposed pictures through my Nikon FE using the Nikon's light meter and shutter speeds and with both set on the same ASA/ISO. The filters that digital cameras have across the sensors have about 2 stops of reduced light filtering to bring the light reaching the sensor to the same as if it were film, so meeting the standard. By taking those filters off the sensor the Nikon is set at say ASA 1600 and the Nex at ISO 400 (& white balance adjustment) to achieve a reasonably exposed picture, albeit in infrared. Thought this may be of interest in this topic to show the relationship of digital sensors to film.
    Robin.
     
  8. flavio81

    flavio81 Member

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    I am amazed that nobody has fully addressed the two or three potential issues here:

    1. The Canon F-1n and F-1 (1976 and 1971, respectively) meters are usually really precise, but they require precise 1.33-1.35V for correct meter operation. This is achieved by either using a Wein cell, or using a Zinc-air cell like the #675, or using a real mercury battery, or (perhaps) internal modification using a diode.

    If this condition is not satisfied, metering will be off. For example, when you use an alkaline (nominal 1.5V) or silver (1.55V) cell on it.

    The Canon A-1 has an internal voltage regulator, it has no problem with alkaline batteries.

    2. The Canon A-1 has a different light sensor than the F-1n. One is a SPD, the other a CdS. CdS sensors are sensitive in different ways depending on the color of the light. Thus, to compare the output of both cameras (A-1 and F-1), ideally DAYLIGHT should be used.

    3. The Canon F-1 has a totally different metering pattern than the A-1. Canon F-1 has a partial metering pattern, where the A-1 is a centerweighted meter. They will not meter the same scene identically, if aimed at the desired framing of the image.
    Thus, to compare the output of both cameras, ideally a flat white screen (lit by daylight) should be used.