EXIF data question, 300D

[petrus]

Hi,
a while ago I discussed the exposure problem, my question was why the one lens over esposed everything and the other did not. Well, I still have the problem, and I try to overcome it by using manual and compensate the exposure by -1 step, which again produces almost too dark pictures under exactly the same condition as the basic setting produces over exposed ones.
The question is about the EXIF data, I cannot quite understand the different parameters, here is one example:
Exposure time is 8s
F-number is 16
... a little later in the column it says
Shutter speed 4s
Aperture value 8.00000
Max aperture 4.970860

The lens is the EF 28-135 IS USM

Can somone explain why there seem to be different Aperture and Time values?

I use AcDSee for quick reviewing of my pictures.

Any advice is much appreciated before I send my camera for 2 -3 weeks to Canon for checking.
:?: :?:

[robertwgross]

What are you using to see the EXIF information, not to review the image?

Why don't you set up a test? Shoot a test subject, and write down all of the information that you can see displayed on the camera display. All of it.

Then transfer that image file to your computer and use your EXIF viewer. Does the information match to what you had at the camera?

---Bob Gross---

[Loekito]

Maybe this is a "dumb" answer, or maybe I too "dumb" to answer :shock:

What mode are you using? are you using auto mode? or you specificaly using creative mode? since if you using auto mode (eg. green, close-up, sports, landscape etc..) the drebel will give automatic metering/calculation, so maybe when you frame your subject, and inspect the metering, you see that figure, but somehow when you release the shutter, there something happend (eg. big clouds passing by) so the drebel was recalculate the metering to get proper exposure, and you don't realize it, so when you download the picture to the PC and inspect the EXIF data, you got different figure.

But basically, what camera show, and the preview (pressing the INFO button during play/preview), and the EXIF should have same information.

regards,

Loekito

[SoCal69]

I can't adress the shutter speed issue, but I can address the Aperature issue...

I seem to recall a thread a while back which covered this issue. If I recall correctly, we figured that the "Aperature Value" was simpy the number of times the aperature area was halved. In other words, if your lens had actual full f-stop clicks, how many clicks from f/1 to f/16. Going from 1 to 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 is 8 clicks or full stops over. Hence your aperature value is 8.0. Seems to me that it isn't all that helpful when the f-stop is already given, but there it is.

Hope this helps.

[petrus]

Hi,
thank you for the comments! I was using creative mode, and the first F and T values where the ones the camera showed and the ones I chose. As I am having pretty heavy exposure problems with all my other EF Canon lenses (they are all brand new) except for the EF 18-55 I have been doing a lot of shooting (gray card and comparing shots of same objects with different lenses and settings). The contradictory informations in the EXIF data made me wonder, if there is a problem with camera after all (and not with my shooting)!

[vvizard]

Just like to shoot in something quick here. EXIF-info can be a pain in the ass when you're programming, and trying to convert raw exif data into something "readable" as end-users see it in their applications. ACDSEE probably is "big" enough to have gotten it right, but smaller hobby-projects might easily fail, and here's why:

About one year ago I was developing a webbased album-application much like "Gallery". I then implemented the function of automatically extracting and viewing exif-info from the pictures. I set it up to work nice with pics from my Minolta Dimage 7i. Later during testing, I acquired shots from both a Nikon D100, and a Canon IXUS. They where all calculating exposure-time differently. If I don't recall wrong, the D100 used to multiply it by 10 (for some reason way beyond my understanding), and Canon / Minolta didn't do things the same either. I simply decided there and then to drop implementing functions for extracting this info myself, but used the opensource program Jhead ( http://www.sentex.net/~mwandel/jhead/ ) to fetch and put them in the right format for me.

The app was written in PHP, and I haven't looked into it since, so I can't rule out that it was a bug in PHP's exif-library (which probably have been fixed now if that was the case) but I doubt it. Different companies seem to use their own "format" in the exif info, and then it's up the the programmers to make sure they support every one of them. So even though it probably isn't the case with acdsee, if you see strange EXIF-info in other less well-known apps, be sure to double-check it with another application, as theres plenty of room to make programming-glitches in that area.

[robertwgross]

Facts are getting confused here.

You stated that your other EF lenses worked one way, but your EF 18-55 worked differently.

Isn't that the EF-S lens, not EF?

I would expect it to work differently.

You didn't state what your heavy exposure problems were.

---Bob Gross---

[petrus]

Yes Bob, you are right - one discussion leads to another and the facts are confused. Let me make a brief summary:
In the beginning I only ha the EFS lens ad I was happy.
I also had the EF 75-300 III, but did not use it much.

Then a few months ago I got the EF 28-135 IS USM and my problem started.
At first only in bright daytime but now also in over cast and shadows (outdoor). The result seemed always to be more or less over exposed.
Example:
In the afternoon (here in Finland it is now light until 8 and 9 pm) normal daylight, but shadow, I shot white flowers in the grass using the 28-135 lens, using 135mm and ISO 100.
Setting Av; F16 and the camera gave me exposure time 8sec! Result - over exposure!!

One minute later under the same condition without changing anything except for changing exposure bias to -1 I shot exactly the same flowers again, and the result was slightly underexposed, F selected was still 16, Av function and the time the camera gave me now was 2sec!

Some testing with the 75-300 also returns over exposed results, but I cannot confirm this with any further tests as I have been concentrating my efforts on the 28-135 which would make an excellt allround lens, if I only could get it working. I also shot 5 pictures with each lens (same series of manual and auto settings for each lens) of a GrayCard in a room with only natural light (no strong sunshine), each and every shot was over exposed, some more, some less but substantially in every case.

After all the tests I have done and the loads of poor pictures and bad results I have lost the confidence in the camera. Either it is too much for me or the camera is really in bad shape! I know the 300D is not a point and shoot, but under normal conditions I should get at least normal "tourist" level pictures in automatic mode .

Bob, I really am grateful for every help I can get!

[robertwgross]

I don't know.

There is a standard problem that lots of new Canon users have. It might be happening to you, and it would be good if we can rule that out.

On the display, the camera tells you an aperture value. It might display 5.6 or something, and that means f/5.6.

Then it tells you a shutter value. It might display 30, and that means 1/30th of a second. Some users think that means 30 seconds, and that is wrong.

You might check and make sure that you aren't getting this wrong. That could explain a lot of things.

---Bob Gross---

[kb244]

I have a Digital Rebel, and I have 3 Sets of Lens, the Kit 18-55, the 28-135 USM IS, and the 50mm 1.8 II. Here are exif info from each ( obtained thru Photoshop CS, the same can be obtained thru windows XP, File property, summary, advanced I'm sure ).

18-55
Advanced Mode - EXIF Properties:

Exposure Time: 1/100
ShutterSpeedValue: 6643856/1000000
FNumber: 56/10
ApertureValue: 4970854/1000000
ExposureProgram: 2
DateTimeOriginal: 2004-04-25T15:20:32-05:00
ExposureBiasValue: 1/1
MeteringMode: 5
FocalLength: 18/1
ISOSpeedRatings (seq container) -> [1]: 100

Camera Data 1 ( I guess this is where photoshop translates the value to something more understandible )

Make: Canon
Model: Canon EOS DIGITAL REBEL
Date Time: 2004-04-25T15:20:32-05:00
Shutter Speed: 1/100 sec
Exposure Program: Normal Program
F-Stop: f/5.6
Aperture Value: f/5.6
Max Aperture Value: [blank]
ISO Speed Ratings: 100
Focal Length: 18.0 mm
Lens: 18-0-55.0 mm
Flash: Blank


Canon 28-135 USM IS
Advanced Mode - EXIF Properties:

Exposure Time: 1/125
ShutterSpeedValue: 6964784/1000000
FNumber: 63/10
ApertureValue: 5310704/1000000
ExposureProgram: 2
DateTimeOriginal: 2004-04-25T15:21:38-05:00
ExposureBiasValue: 1/1
MeteringMode: 5
FocalLength: 95/1
ISOSpeedRatings (seq container) -> [1]: 100

Camera Data 1

Make: Canon
Model: Canon EOS DIGITAL REBEL
Date Time: 2004-04-25T15:21:38-05:00
Shutter Speed: 1/125 sec
Exposure Program: Normal Program
F-Stop: f/6.3
Aperture Value: f/6.3
Max Aperture Value: [blank]
ISO Speed Ratings: 100
Focal Length: 95.0 mm
Lens: 28.0-135.0 mm
Flash: Blank


Canon 50mm f/1.8 II
Advanced Mode - EXIF Properties:

Exposure Time: 1/800
ShutterSpeedValue: 9643856/1000000
FNumber: 18/10
ApertureValue: 1695994/1000000
ExposureProgram: 3
DateTimeOriginal: 2004-04-25T14:04:36-05:00
ExposureBiasValue: 1/1
MeteringMode: 5
FocalLength: 50/1
ISOSpeedRatings (seq container) -> [1]: 200

Camera Data 1

Make: Canon
Model: Canon EOS DIGITAL REBEL
Date Time: 2004-04-25T15:20:32-05:00
Shutter Speed: 1/800 sec
Exposure Program: Normal Program
F-Stop: f/1.8
Aperture Value: f/1.8
Max Aperture Value: [blank]
ISO Speed Ratings: 200
Focal Length: 50.0 mm
Lens: 50.0 mm
Flash: Blank



Another thing to keep in mind, is that those values were obtained once I opened the raw for each picture, I noticed that when saved as a jpeg there is slightly more information, possibly in older Tiff-like format. Hopefully the information above will help you determine differences. The big numbers are usally for computer/application understanding and not so much human eyes, the Camera Data section in Photoshop CS I'm sure is where the human eye needs to look to get a more understandible interpretation of the data.

[petrus]

Thank you all,
having photographed with different setups (Dimage7i, Nikon F, Olympus OM2 etc), all the basics are quite familiar - just in the case of EOS 300D I meet the above related problems. So took the camera to the service depot today for checking.
:roll: