This article is an attempt to explain more clearly what all the data strings mean in the Exif data of a digital photograph. i will try to explain what each string of data found in the photograph means. Also ill try to expel some myths in regards to the data.

First thing Exif stand for Exchangeable image file format. What this file will show you in relation to your digital photo, is strings of data recorded when the image was taken by your camera. Such things as, time and date, make and model of the camera, aperture size, focal length, exposure length, and numerous other strings of data. I will include an example of a typical Exif data sheet in this article.

Now, it is rumoured that since the aid of Exif data that the use of a digital camera is just as good if not better than a standard 35mm camera. Reasons for this, is it is claimed by some that the Exif data is now able to be used as a kind of digital negative for the photo. That if any manipulation was done to the image that the Exif data would indicate it. This on one level is some what correct. We can use the data for this purpose to an extent, but its not fool proof.

There are now programs that allow you to edit Exif data. I have tried out a couple of these programs to test what they can and can not do. I found the ones I tested to have a steep learning curve. Making it a bit to much work for a person to use just for the purpose of fabricating a paranormal photo. This isn't to say it cant, wont, or hasn't been done though. I'm not going to go into a lot of detail about these programs because for the real paranormal investigator or researcher we wont have any need for these programs.

If the Exif data is utilized by the serious investigator to be used as it was designed for. Then it has its place, use, and aid in our arsenal. And that is used to help in the recreating or analysis of a digital photograph. I highly recommend you use the information for trusted persons. It can be used as I said earlier to expose fabricated images, but its not fool proof, be sure, before you call someone out on an image.

Exif data has helped me in my analysis of a photo on more than one occasion. Specifically awhile back the paranormal community was being flooded with these new images of what was describe as "super charged orbs". Basically a photo showing generally a orange light streak across the image. We still see these images occasionally, and well some groups still even use these as positive evidence of the paranormal. But with the aid of the Exif data, I was able to find the cause for them. It was quite simple really, all these images generally have 2 common strings of data. One being that the cameras "night scene" function was used. The second being that the exposure of the photos were of considerable length as far as a camera is concerned. Anything over 1/30th of a second is considered in my opinion to long of an exposure, that is with out a tripod. If a tripod is used exposure can be used at any length really. Night scene is designed to extended the exposure to allow more light into the camera so it can expose a darkened image better. It is not night vision and should always be used with a tripod, I cant say this enough.

Here is a typical layout of a Exif data sheet.



As you can see, there is quite a bit of data associated with just a single photograph. All of this data is useful especially when trying to recreate a photo. What im going to do, is go down the list of data a string at a time and describe what each section means and what's its for. I hope this will aid you in understanding Exif data.

Main Information

-Image Description- This is pretty straight forward. Its telling us the maker of the camera. With an editor this description can be changed to describe your image. The line of data we see in this specific data sheet is most likely a default entry made by the camera.

-Make- This line as well is telling us the maker of the camera. This is where you would normally find this information, where as the Image Description section would normally be blank or have an entered description of the photo.

-Model- This as well is pretty straight forward. Its the model number of the specific camera that took the photo. Even though these last couple of strings of data the Make and Model of the camera seems straight forward and some what basic. These two strings are important. Specially if analyzing a photo from some one else. You use the Make and Model to look up information on that specific camera. This aids us in a couple of ways. We can find out if there are any known defects in the camera that may be causing odd anomalies in resulting photos, or recalls, or look up detailed manufacturer specifications on the camera.

-Software- This string is telling us the software the camera has used to process the image. It is internal already on the cameras system. This is not indicating some form of software was used in any manipulation of the photo. Its the manufacturers software inside the camera that controls its numerous functions.

-Date Time- This is the date and time the photo was taken. This is useful if you keep your date and time up to date on the camera. Most people don't, but a good investigator should always make sure this is accurate, it can and will help later in an investigation. If you change your batteries, make sure to update the internal clock of the camera.

Sub Information

-Exposure Time- This is telling us the amount of time the shutter of the camera was opened to allow light into the camera onto the image sensor, to produce the image. For a photo to expose, light is needed. The amount of light is regulated by a few components of the camera. The shutter, aperture, and f stop (though this is really not a component). The amount of light that falls onto the digital cameras image sensor will expose the image. By exposure time, we are talking about the amount of time this light is on the image sensor. The camera generally calculates this time in seconds, or split seconds.

-F Number- This is telling us the diameter size of the aperture of the camera. The aperture is essentially the eye of the camera. This eye is what allows light in, or regulates the amount of light to enter. Apertures adjust in size depending on the mount of light you want in. or the camera will allow in on a specific setting. The F Numbers describe the size of the aperture at the time the photo was taken. In F Number's the smaller the number, the larger the aperture is opened. The larger the aperture is opened the more light can enter. In darkened conditions we want to use the smallest F number we can on our cameras.

-Exposure Program- This is indicating the setting used on the camera at the time the photo was taken. A lot of digital cameras today come with many different settings that can be used. Like, night scene, creative, sepia, black and white, and in this case shutter priority. This string of data is just simply telling us what setting was used at the time the photo was taken. Each setting will have its own default settings as far as aperture, f number, focal points, etc.

-ISO Speed Rating- This is telling us the sensitivity of the cameras image sensor to light at the time the photo was taken. Its similar to film ISO Speed, and yet still different. Were talking chemicals and pixels. Smaller ISO Speeds are used when a location is well lit with bright lights. The larger ones are for more darkened conditions. Higher the ISO Speed the more light is allowed to enter. To read more on this I recommend this web site http://www.cameratown.com/guides/iso.cfm

-Exif Version- This is telling us what version of the Exif standard this particular camera is using when writing its Exif data and displaying it.

-TimeDateOriginal and TimeDateDigitized- This is telling us again what the time and date was when the photo was taken. If manipulation to a photo was done. Often times you will see a different time and date stamped here than in the original time and date stamp. This should always be looked at when analyzing photos. To compare time stamps.

-Compression Bits Per Pixel- This is telling us the amount of compression the digital photo has had from the cameras internal storage. Watch this, to much compression can result in loss of quality in the photo.

-Exposure Bias Value- This is telling us the amount of exposure compensation this photo was given by the camera. As we can see this photo didn't have any. But you can adjust on some digital cameras the amount of exposure compensation you wish to give a photo. Basically to help the exposure of a given subject. This is a setting most of us wont use. But could be quite handy on site if you had the patience to learn how each adjustment effected a given photos lighting conditions, and knew how to apply it on site. The values are referring to different combinations of shutter and aperture speeds. If the photos you have been taking are appearing over exposed (too much light) decrease the exposure value. If their appearing under exposed (to dark) increase the exposure values then. That is, if your camera allows you to make these adjustments manually.

-Maximum Aperture Value- This is telling us the maximum size our aperture can go on this specific camera. As we can see this photo used the maximum size of its aperture at the time, by going back up and looking at the F Number.

-Metering Mode- This is telling us what metering mode the camera used in determining the correct exposure of the image. This photo used division. I'm not exactly sure what the division metering mode is, or more so, what area of the viewfinder the meter used. Basically what metering does is allows your camera to focus in on a specific area of the view finder so as to measure lighting, in order to set the correct exposure for the specific setting used. Generally there are 3 different metering modes. Spot, centre-weighted average, and multi-zone. Spot is generally just a small portion of the centre of the viewfinder, though some cameras allow you to move this spot around. Centre-weighted average, is similar to spot but has more of a feathering look to it from the centre working its way out. Multi-zone does what its called basically. It meters multiple areas of the viewfinder in order to find the best exposure. This is also typically the default metering program on most cameras.

-Flash- This section indicates if the cameras flash was used or not. some times you may see flash being indicated it was used but with a side note of compulsory. This means flash was forced, it had to be used.

-Focal Length- This is telling us the size of the portion of the lens that was used in focusing the image properly. There is a lot more detail about focal length. To much for me to write here I'm afraid, so I encourage you to go to this web site and read more if your interested. http://en.wikipedia.org/wiki/Focal_length

-Exif Image Height and Width- This is telling us the size of the photo in pixels.


Vendor Original Information

-Mode- This is telling us the cameras mode or setting that was used. Such as creative, night scene, etc. As we can see the normal default setting was used for this image.

-Quality- Pretty straight forward. Its telling us the preset quality that was used for this photo. Most cameras come with varying quality settings to allow you to take more photos of lesser quality, or lesser photos of higher quality. Its more so for storage. In our field, I highly recommend you go with the highest quality photo over the more quantity. Use more cards if you need to. But if you get that great ghost photo using a low quality setting on your camera to conserve space, you'll be kicking your self in the morning.

-Macro Mode- Anyone into photography knows what a macro is. It is a close up of your subject, an extreme close up, showing all the very small details. Traditionally it for taking photos so close that they are real life size. We shouldn't even encounter a need for macros in this field though. But fun to play with it.

-Digital Tele- This is the cameras digital zoom that most digital cameras have. Its recommended when using your zoom lens on your camera don't go into the digital zoom. It will only further pixelate your image, making it quite blocky, and losing a lot of detail.


The rest of the data on this particular sheet is of no concern really.

Now, some people may not know where to access this information about their photos. I highly recommend the use of the program I use in doing so. Its called EXIF Reader. The author of the program offers a free version with no strings attached. I've been using the free version for years, and should probably donate to the man or buy the full version at some point. But anyway, its a great program for looking at the Exif data of a photo and very easy to use. It can be found here. http://www.takenet.or.jp/~ryuuji/minisoft/exifread/english/

I hope this article is able to help explain a bit more what Exif data is and does. Thank you for reading.

© Terry Moore - A.R.E.A. Paranormal 2/17/07