What use is EXIF?

[walwyn]

From time to time I get asked questions like: There is no EXIF data with the file what exposure did you use?

Its a question I don't really understand. I mean even if I tell you that a particular shot was taken at 1/100 sec at f8.0 what useful information does that convey? Similarly if one knows that an image in the gallery was taken with a Dodo 100-300 zoom XT lens, what use is that?

My personal opinion is that, despite the fact that such data gets pasted by rote into all photographic books and magazines, it is for the most part useless noise.

Can anyone tell me what practical use it actually has.

[Canis Vulpes]

EXIF is data tagged to the image file. Data recorded is mostly about the camera settings that were used to take the picture, hence the question you quoted. 'There is no EXIF data with the file what exposure did you use?'

I think this site sums the EXIF situation quite well.

http://www.exif.org/

a joy of WPF is learning from other people wiling to share their knowledge rather than keep it close to their chests. I have found it very useful knowing what camera, speeds etc have been used and what proportion of the frame is actually represented. I hope it shows in what I see as a huge improvement in my pics since I joined, and now helps in passing on what I have learnt to newcomers who one recognises as taking the earlier steps on the path.

I also post occasionally on WildAboutBritain where the exif is jumbled and that is one of the reasons I have gradually spent less time there and more here

[walwyn]

Perhaps I wasn't clear, but I do know what EXIF is. What I don't understand is how it can be considered useful to anyone? What use can the exposure data for this

http://www.fotograffiti.it/albums/An..._Mountains.jpg

or any other photo be put to?

[Don Hoey]

Seems Chris posted while I was typing so I'll go with what I have written. Sorry if I repeat anything Chris.

On the forum I find them interesting. It is not that I intend to memorise and copy them for a given situation. However I did use some as a starting point for my first moon shots.

Examples :

I always read Foxy's and have come to greatly admire the capabilities of his D2Hs. Now is there any benefit in that. YES. If I contemplated getting that camera, and I very nearly did but opted for the D2X instead. Once again Foxy's images amongst others helped sway that decision.

Similarly Leifs images. Leif is a Nikon man the same as me. I looked at his pics taken with the Nikkor 200mm macro and have compared bokeh with shots posted with the 105mm VR macro. If I was in the market for an upgrade of my macro then his pics would probably swing me towards the 200mm.

If I was thinking of attending an airshow, and we have talked prop blurr in posts before, then I would do a trawl through the gallery to check out approprite shutter speeds. I could say the same for blurring water over a fall. These are things I do not have in my head. Give me a subject and a flashgun or two and I don't even have to think about anything. Others however may.

Generally creative use of focal length, shutter speed or aperture is something that the exif can show up. Some of Robs images to name but one of several fit that bill.

On the fun side how will I know someone is posting images with an undeclared new toy.

Outside of the forum then I am helping Ros. She is currently using the camera in simple program mode until she can digest and make sense of info on the relationship between shutter speed, aperture and ISO. Without the exif to refer to on pics she e-mails me then I would have no idea what shutter speed and aperture settings the program selected to be able to offer advice. So if the picture is blurred, was it incorrect point of focus, or too low a shutter speed for the focal length used, possibly agravated by a low an ISO setting. All info in the Exif. Without going through the Critique Forum I am sure there are pics posted where that same info has been helpful in someone providing reasoned help.

Don

[miketoll]

It is very useful to learn from. Say I take a macro shot but there is not enough depth of field I can look at the data and know that next time what f stop would be better at that distance and with that lens or perhaps I want to know what shutter speed I used on that pan shot that worked so well. A helpful tool to build up experience and knowledge with.

[Don Hoey]

Originally Posted by walwyn

Perhaps I wasn't clear, but I do know what EXIF is. What I don't understand is how it can be considered useful to anyone? What use can the exposure data for this

http://www.fotograffiti.it/albums/An..._Mountains.jpg

or any other photo be put to?

No exif in that, but as its Ansel Adams then he was probably using a 10 x 8. A google of Ansel throws up thee images at the top of the page. Now if you look at the middle image aperture would certainly be interesting and that would probably be f64. So I have guessed at 10 x 8 camera and an aperture of f64 but if you were into that format then the lens used might also be of interest. Also dare I mention film type.

No exifs in those days. You had to buy his books and I did. Did I learn anything ............. I hope so.

Don

[walwyn]

Don,

The problem though is that if he took the photograph 10 minutes later or earlier the exposure would have been different. In addition we're not seeing the PP work that went into producing the image, the time the plate spent in the developer, the type of developer, or the dodging and masking involved in the printing. In addition to exposure being situational and transitory, we have no idea where he took the reading from, nor whether he overrode what the meter told him.

[Gidders]

Originally Posted by walwyn

Don,
The problem though is that if he took the photograph 10 minutes later or earlier the exposure would have been different. In addition we're not seeing the PP work that went into producing the image, the time the plate spent in the developer, the type of developer, or the dodging and masking involved in the printing. In addition to exposure being situational and transitory, we have no idea where he took the reading from, nor whether he overrode what the meter told him.

What you say is absolutely correct but... even without the exif we can say that he used a small aperture (because of the depth of field) and slow shutter speed (because of the movement in the cloud). If his intention was depth of field, then an exposure 10 minutes earlier or later would have had the same aperture but a different exposure time. Conversly, if his intention was a certain degree of movement in the clouds then his exposure time would be fixed and nthe aperture varied.

If someone wanted to take a shot similar to the one I posted of water moving over rocks the exif tells us that this was taken at 1/13 sec. OK some rivers move faster or slower but it gives someone else a starting point. Similarly to freeze the action at the Appleby horse fair I used a 1/500 and to get this perspective in Victoria Square I used a 10mm lens on a 1.6 crop factor body.

I cant remember all that sort of information but the exif records it for me so I can learn for the future, and help others. Now OK Ansel Adams didn't have the luxury of cameras that encoded the exposure info into his negatives, but I wouldn't mind betting the he, and other greats of the times, kept records of how their images were captured.

Post processing, whether it be in the dark room or digital, can affect things like the brightness, or contrast the image, but they cant change perspective (lens choice) or depth of field (aperture - unless focus stacking is employed) of freezing of action (shutter speed)

[walwyn]

At the back of my mind (from some 25 years ago) I recall blurry water 1/4 second. But as you say it all depends on the rate of flow, and the amount of blur required. Go back a month later and the flow rate will have changed, the light and mood will be different and a different length of time will be optimal for the moment. So you bracket on length of time, you're not going to set up camera and tripod dial in 1/13 second press the shutter and pack up.

I don't know, perhaps there are novices that look at EXIF data to use as a starting point, but I suspect they're more likely to have got a book on photographic technique out of the library, which has told them: blurry water long shutter speed.

I suspect they are also more likely to read "landscape photography: set white-balance to cloudy" than to ascertain that from EXIF data.