Metering Revisited (or The Story of Why I Have an 18% Gray Card)

I’ve had to delve further into metering, or more correctly, into inaccurate metering, than I cared to. While shooting film for the SR-3, I decided to do a few studio shots with the SR-3 and a Minolta 8000i. The SR-3 is from 1960 and has no internal meter, so I had to use a metering app. I thought I solved my metering dilemma last year. There are two metering apps on my iPhone: Pocket Light Meter and myLightMeterPro. Both work well but don’t always agree. 

On this particular day, I was shooting in the late afternoon and evening, and window light was unavailable, so I decided to try a few low-key shots. It was my new-to-me Minolta AutoMeter III, an incident meter, that emboldened me to try low-key. These Minolta meters, though decades old, still command a decent price, and depending on the model, they go from 50.00 to 300.00. Mine cost 20.00, which should have been a hint. Of course, the seller assured me it worked flawlessly.  

I composed a scene solely to use the AutoMeter III and try low-key. The first shot metered at 1/60 of a second at f5.6 (400 ISO). It seemed a little fast given the light, but using the SR-3, I took the shot. Then, becoming even more suspicious, I tried again but at 1/30. Still thinking something was amiss, I put a lens on the 8000i, and it metered the scene at 1/4 second at f5.6. My fancy AutoMeter III consistently read four stops faster than the 8000i. I found this hard to take so, out came the iPhone.  

The iPhone apps only made things worse. Pocket Light Meter read 1 stop faster (1/8 second) than the 8000i, myLightMeterPro read 1 stop slower (1/2 second). By this time, I had spent 30 minutes on what was supposed to be a quick shot. Of course, everything came to a halt because I had no idea which to believe. Finally, I opted for Pocket Light Meter to finish the roll.  

Later that evening, upset about the AutoMeter III being basically useless, I searched online for help. A few suggested tweaks seemed to help some, but what helped most was an accidental fall. After that, the AutoMeter III was off by only two stops compared to Pocket Light Meter. Still dissatisfied, I ordered an 18% gray card and a Luxi dome. Both iPhone apps had settings for the Luxi, allowing them to be used as incident meters. My plan was to hold a face-off between the AutoMeter III, the iPhone apps with and without the Luxi dome, the 8000i, the Sony a100, and the Minolta Maxxum 7D.  

I used three light sources: direct light, ceiling light on the grey card, and light reflected from the wall (yellow). Each device was set to 400 ISO with an aperture setting of f5.6. I used the Sony a100, the newest of the cameras, for the initial set of readings. The a100 gave 1/4 second for the grey card and 1/15 second for the wall. The readings changed appropriately for the direct light. The Maxxum 7D agreed with the Sony. At first, the 8000i was way off, but I checked, and the ISO was 100. Once I set the ISO to 400, the 8000i agreed with the other cameras.  

Next, I took incident readings with the AutoMeter III. It read 1/15 when placed next to the gray card and 1/60 when placed next to the wall. It was off by two stops but consistent, so I took some comfort in that. Next, I tested the iPhone apps with and without the Luxi dome. Pocket Light Meter agreed with the cameras when reading with the gray card as a reflection meter and as an incident meter with the Luxi dome. myLightMeterPro was a stop slower. Finally, I took pictures with the Maxxum 7D to make sure it was properly exposing, and the images were fine.  

So what have I learned? First, test any new meter to make sure it works properly. I’ve checked multiple times since that day, and my AutoMeter III is consistently off by two stops, so it is useable with that caveat. To avoid mental gymnastics, I set the ISO two stops slower (from 400 to 100 ISO) so that it agrees with the rest of the group. The meters in the Sony a100, Maxxum 7D, and Maxxum 8000i are reliable. The Luxi dome is well worth the 20 dollars I paid for it (Amazon). myLightMeterPro can be calibrated, which I did. Now, it consistently matches the cameras and Pocket Light Meter.  

I wanted an incident meter, and the AutoMeter III, which looks as if barely used, is a mild disappointment. But much less so than if I had paid the full market price (usually about 75.00). Also, now that I know to set the ISO lower, using it is a breeze. The Luxi dome was a big surprise. I never expected it to work so well. My only complaint is that it seems easy to lose (it slides around easily). If the AutoMeter III dies, it will not be replaced.  

I have now tried four iPhone metering apps, multiple camera meters, one analog and one digital hand-held meter, and Luxi. Going forward, I will trust my Maxxum meters. Pocket Light Meter is the winner for walking about. When I need to be finicky about light in the studio, I will use an incident meter—Luxi + iPhone app or the Minolta meter.    

The End.


  1. Yikes! Sorry to hear about all that drama.

    I’ve pretty much relied on the “in-camera” meters for my shots. I’ve used the Lux phone app for my meterless Agfa Isolette, and it seems fine.

    I’ve been looking at eBay for light meters and am amazed the prices some of them command. I even thought about a brand new one, but good luck finding one for under $100.

    I did pick up a 60s era Sekonic selenium cell one for just $10 (shipping included). I haven’t really tested it yet. If anything, at least it looks cool…

    1. Yeah, the in camera meters for my Maxxums seem to be very accurate, and those with spot metering are dead on. It is the older cameras without spot metering that raise a concern. This episode was a pain, but I did learn a lot from it, so I am happy with the outcome. Also, I can use the 18% grey card to set exposure when trying to shoot my deep red crocosmia.

      1. I don’t feel like I’ve been let down by the in-camera metering in any of my cameras, except when the lighting is particularly tricky, like if backlit. Then again, I don’t do flower macros like you!

        1. Hey, I’m still a rookie—I may be doing it wrong. LOL

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