Learning Photography Through EXIF Information

February 12, 2010February 12, 2010 TCDavis

EXIF stands for “Exchageable Image File Format”. EXIF information is embedded in the code of photos taken by most digital cameras. If a Flickr member has allowed “More Properties” to show in his/her photo stream, then viewers can see EXIF information by clicking on “More Properties” under “Additional Information”, to the right of each photo.

So, why is EXIF information so important? Because it reveals lots of technical details about how a photo was taken. Let’s use one of my recent photos as an example:

Below is the EXIF info for that picture:

Camera:
Nikon D200

Exposure:
0.02 sec (1/50)

Aperture:
f/16

Focal Length:
270 mm

ISO Speed:
250

Exposure Bias:
0/6 EV

ISO Speed:
250

Orientation:
Horizontal (normal)

X-Resolution:
72 dpi

Y-Resolution:
72 dpi

Software:
QuickTime 7.4.5

Date and Time:
2008:05:07 10:45:08

Host Computer:
Mac OS X 10.5.2

YCbCr Positioning:
Centered

Exposure Program:
Manual

Date and Time (Original):
2008:05:08 08:41:40

Date and Time (Digitized):
2008:05:08 08:41:40

Compressed Bits per Pixel:
4 bits

Maximum Lens Aperture:
50/10

Metering Mode:
Pattern

Light Source:
Flash

User Comment:
(c)TCDavis:tcd123@alumni.pitt.edu

Sub-Second Time:
90

Sub-Second Time (Original):
90

Sub-Second Time (Digitized):
90

Color Space:
sRGB

Sensing Method:
One-chip colour area sensor

Exposure Mode:
Manual

White Balance:
Manual

Digital Zoom Ratio:
1/1

Focal Length In 35mm Film:
405

Compression:
JPEG

Colour Mode:
COLOR

Quality:
FINE

White Balance:
FLASH

Sharpening:
AUTO

Focus Mode:
AF-S

Flash Setting:
NORMAL

White Balance Red, Blue Coefficients:
514/256, 300/256, 256/256, 256/256

Thumbnail IFD Offset:
2354

ISO Speed Requested:
250 (May be different to Speed Used when Auto ISO is on)

Photo corner coordinates:
0, 0, 3872, 2592

AE Bracket Compensation Applied:
0/6

Tag::Nikon Type 3::0x001B:
0, 3904, 2616, 3904, 2616, 0, 0

Tag::Nikon Type 3::0x001E:
1

Tone Compensation (Contrast):
AUTO

Lens Type:
14

Lens Min/Max Focal Length, Min/Max Aperture:
700/10, 3000/10, 45/10, 56/10

Bracketing & Shooting Mode:
Shooting Mode: Single Frame AE/Flash Bracketing Off White Balance Bracketing Off

Tag::Nikon Type 3::0x008A:
2

Colour Mode:
MODE1

Lighting Type:
NATURAL

Noise Reduction:
OFF

Tag::Nikon Type 3::0x009A:
605/100, 605/100

Tag::Nikon Type 3::0x00A2:
4818821

Tag::Nikon Type 3::0x00A5:
18426

Total Number of Shutter Releases for Camera:
18426

Image optimisation:
NORMAL

Saturation:
AUTO

Image Width:
3872 pixels

Image Height:
2592 pixels

This photo was taken with a Nikon D200.

Secondly, the exposure time was 1/50th of a second and the aperture was F/16.

Next you learn that the picture was taken at 270mm of focal length. That won’t tell you what kind of lens I used, but it does reveal that it’s a mid-range telephoto. Now, if you know something about taking telephoto shots, you will deduce that I used a tripod for this shot, because 1/50th of a second would be much too slow a shutter time at this focal length to get a good clear shot handheld. I had to be using a tripod. And indeed, I was.

Next you notice that I used an ISO setting of 250, which isn’t very high, given this back-lit shot. I wanted to keep visual noise down (that speckly texture in the background of some shots), so I chose a relatively low ISO.

You will note that the exposure program was Manual. This means that I made all the settings myself: aperture, shutter speed, ISO value, and White Balance. Notice that the light source says “Flash”. Actually, I didn’t use a flash in this shot, I used natural back lighting by the morning sunshine. However, I made a White Balance setting error, and set the camera for flash instead of for cloudy conditions. (Sometimes I choose the cloudy setting, even if it’s sunny outside, because the cloudy setting brightens a photo to the red end of the spectrum, and I wanted the warm red of the leaves to be enhanced. I erred in the setting, but the photo turned out O.K. anyway, because those leaves had plenty of warm red on their own!

Next, notice the user comment line. I have programed my camera to indicate that each and every photo is copyrighted by TCDavis. My email address follows, in case anyone viewing the EXIF info wants to contact me regarding the use of a photo. On Flickr you will notice that some photographers stamp their copyright on their images. I choose, rather, to embed my copyright in the EXIF info, because it cannot be cropped away that way.

Finally, you will notice the image width and height. This is the width and height of the original shot, not after processing. By looking at these original dimensions you can tell pretty well whether a shot uploaded to Flickr has been cropped or not.

Well, that’s a lot of information, and I haven’t even mentioned all that is in the EXIF information of the Redbud photo. For the purposes of learning, however, the most important items are aperture, shutter speed, ISO setting, and exposure program type. These will tell you a lot about how a photographer achieves his/her shots.

When I was learning how to freeze birds in flight, I looked at the EXIF info on some sterling flight photos and saw that I had to use a shutter speed of at least 1/1000. I’ve also learned that to get good depth of field, one should use a narrow aperture; say, F/16 or higher. In the Redbud Leaves photo I was mostly interested in getting good depth of field, because not all the leaves were equidistant from the lens, and I wanted as much clarity in each leaf as possible.

As you are learning from other photographers in my Flickr  group, Better Web Pics, or just browsing around Flickr, take a look at the EXIF information. You can learn a lot from what you find there.