Meta-Metadata
By Marc Rochkind
At first there were only the images themselves, maybe with some shooting or processing data about them if the photographer remembered to record it. Ansel Adams was careful to record exposure, but had an "unfortunate disregard for the dates of [his] negatives" and an "anti-date complex" (his words, in Examples: The Making of 40 Photographs, pp. 42–43; many years after Moonrise was taken an astronomer calculated its time as 4:05 p.m. on Oct. 31st, 1941).
With a digital camera, it's as hard as ever to take pictures as good as Adams', but it's a lot easier to record the shooting data. The camera stores it automatically inside the image file. This so-called EXIF data is data about image data (the pixels themselves), or metadata. Most viewing applications display metadata for an image, and so do websites like SmugMug and Flickr.
Cataloging applications like Lightroom, iView/Expression Media, and Aperture go much further: They maintain a database of images, including image metadata. That's data about data about data, or meta-metadata. You can see a bit of this in Lightroom if you open the Metadata Browser (Library module, bottom left), which lists interesting facts like the number of images for each camera and lens.
Even better, Lightroom (and Aperture) use the free and open SQLite3 database, so it's very easy (for a programmer, anyway) to access their catalogs. Although Adobe doesn't document the structure of Lightroom's database, it's not hard to figure out. You can use free utilities like SQLite Database Browser (sourceforge.net/projects/sqlitebrowser) to look at the structure of the database tables and the data that's in them.
That's what I did to develop a small application I call ImageReporter. It shows a lot more than Lightroom's Metadata Browser (such as the average aspect ratio after cropping), and it also lets you filter the report by type of image (DNG, JPG, etc.), by rating (1 star or more, etc.), and by time interval (last 30 days, last 90 days, etc.). You can get a free copy of ImageReporter for the Mac or Windows at ImageIngester.com. If you just want to look at a sample report, I've posted one of my recent ones here.
It's fun to look at the metadata summaries in Lightroom's Metadata Browser or with ImageReporter, but it's even more interesting to discover things about your photography from them. I'll give two examples of what I just learned.
First, from ImageReporter's section on focal length, which shows what focal lengths zoom lenses were set to:
662 NIKON CORPORATION / NIKON D200 / 17.0-55.0 mm f/2.8
245 37% 20mm
152 22% 30mm
109 16% 40mm
43 6% 50mm
113 17% 60mm
This is almost the only lens I use on my D200, and the only zoom. The data (meta-metadata, but I'll keep things short) shows that I'm using the lens as a wide angle. I didn't know that! I probably should think about getting a 12–24 zoom, since I appear to be at mostly wide-angle focal lengths. Maybe I really want to go wider and can't?
Cropping is OK if the alternative is getting wet or showing a beer can.
Otherwise, it's better to move your feet.
Second, I'm cropping too much! Look at this data from ImageReporter's "Average Crop of Images That Were Cropped" report:
81% [unknown]
90% Canon / 8400F
43% Canon / Canon EOS DIGITAL REBEL XTi
64% Canon / Canon PowerShot G9
76% CASIO COMPUTER CO.,LTD. / EX-S500
55% FUJIFILM / FinePix S5700 S700
70% Leica Camera AG / M8 Digital Camera
95% Minolta / DS Dual4
69% Minolta / Scan Dual IV
59% NIKON / E3100
60% NIKON CORPORATION / NIKON D200
58% NIKON CORPORATION / NIKON D70
51% Panasonic / DMC-LX2
With my Leica and its 35mm lens (the only one I use), I'm cropping to 70% (by area). With my D200, I'm cropping even more, to 60%. Not only is that with a zoom, which ought to allow me to fill the frame, but the focal-length data I showed above says that I'm at the wide end of the range. Sure seems like I ought to do more careful visualization before I click the shutter and probably zoom in a bit.
Maybe the problem is the aspect ratio? With a 1.5:1 image size, which is what the Leica M8 and Nikon D200 both use, you're forced to crop if you want a more squarish image. ImageReporter has an aspect ratio report, too, part of which shows:
1.41 Leica Camera AG / M8 Digital Camera
1.46 NIKON CORPORATION / NIKON D200
No, it's not an aspect-ratio issue, because I'm typically cropping to close to 1.5:1 on the D200.
What about my better images? Maybe I'm doing extreme crops on snapshots, but I set up more carefully when I'm really trying? Turning on the 4-star-or-more filter, I see (in part):
78% Leica Camera AG / M8 Digital Camera
68% NIKON CORPORATION / NIKON D200
That's a little better: 78% and 68% vs. 70% and 60%. What's more, my better images are less than 1.5:1, especially with my D200, which means there was a method to my cropping:
1.43 Leica Camera AG / M8 Digital Camera
1.27 NIKON CORPORATION / NIKON D200
Still, the data shows that I need to move my feet more when I'm shooting with the Leica, and, with the D200, I need to do that and also zoom in. Maybe I don't need that 12–24mm zoom after all.
You can also use meta-metadata to learn about other photographers. I just got 580 original JPEGs shot by the photographer my niece hired for her wedding last June. I imported them into Lightroom, assigned them to the Quick Collection, and then used an option in ImageReporter that limits its scope just to that collection. Looking at the report, I now know a bit about how that photographer worked.
He used two camera models, a Canon 30D and a 1D Mark II, using the latter for 79% of the shots. Lightroom didn't record the serial numbers, so I don't know if he had one or two or each. Lightroom didn't pick up any lens data, either, so I don't know what lenses he was using. But here's the focal-length data that ImageReporter collected (it rounds to the nearest 10mm, to help the grouping):
123 Canon / Canon EOS 30D
50 40% 30mm
19 15% 40mm
8 6% 50mm
11 8% 60mm
15 12% 70mm
20 16% 200mm
457 Canon / Canon EOS-1D Mark II
101 22% 20mm
38 8% 30mm
45 9% 40mm
20 4% 50mm
18 3% 60mm
39 8% 70mm
9 1% 80mm
37 8% 90mm
20 4% 100mm
11 2% 110mm
8 1% 120mm
10 2% 130mm
16 3% 140mm
14 3% 150mm
9 1% 160mm
11 2% 170mm
4 0% 180mm
6 1% 190mm
41 8% 200mm
The two bulges (8%) at 70mm and 90mm make me think that this photographer used two zooms on his 1D (or two 1D cameras), a 24–85mm (rounded to 20mm and 90mm) and a 70mm–200mm. That would make sense for a wedding photographer. If Canon made a 24–200mm, he'd probably buy one.
The 30D (or maybe two of them) looks like it may have had a zoom from around 30mm to 70mm, stopping there because there are no shots between 70mm and 200mm. It's probably not a 24–70mm, because ImageReporter says there were 50 shots taken within 10mm of 30mm and none wider. It must have been Canon's 28–70mm ƒ/2.8. Indeed I found at least one shot made with that camera at 28mm and ƒ/2.8, so it could not have been a slower zoom. The gap from 70mm to 200mm means either that he put a 200mm prime lens on a 30D or he had the 70–200mm on the 30D zoomed all the way in while he had the wider zoom on another body. This makes sense, and is probably part of his normal work pattern during certain parts of the wedding. If I spent more time on the photos themselves I could probably figure this out for sure.
I didn't pay that much attention to the photographer during the wedding, but it's definitely interesting to find out a bit about how he worked from his meta-metadata.
I found out some things about my own shooting, too. I don't need a full-frame 35mm digital, or even a medium-format digital back, at least not yet. All I need to do is try harder to compose in the viewfinder instead of in Lightroom.
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Marc
