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07-22-2010, 05:06 PM   #1
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Is EXIF important to you?

I'm debating whether or not to get my lens serviced for 145$ at the tech place.

Currently the EXIF data will show 50mm for anything above 50mm on my 17-70mm lens, and 18mm for anything wider than 18mm.

It's rated at 2.8-4 but at 70mm it will go to 4.5.

There's nothing wrong with the pictures, but I'm not too sure if 4.5 is really 4.5 or just 4. The guy I bought it from helped send an email to Sigma asking what needed to be fixed, and he said that the guy said the circuit board needed to be replaced which is the price above.

While there is nothing adversely wrong about this lens, is EXIF data really important?

07-22-2010, 05:21 PM   #2
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I use EXIF a lot to figure out what I did wrong with my settings (fl vs. shutter speed).
As far as getting your lens repaired, that is up to you.

Cheers, Mike.
07-22-2010, 05:37 PM   #3
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Are you sure there's nothing functionally wrong? Shake reduction uses the focal length to determine how much correction to apply, so if the lens is reporting that incorrectly, you may get bad results.
07-22-2010, 05:39 PM   #4
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I keep a spreadsheet of the exif data generated by Pentax Photo Browser, but I do not use it very much at all.

07-22-2010, 05:56 PM   #5
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You may also be seeing the limitations of whatever you are using to read your EXIF, rather than any flaw in the camera or lens.

One of my Sigma zooms, an ancient and cheap 100-300 UC zoom, always gets reported in the EXIF as a much more fancy and expensive lens, a 70-200 f2.8 Sigma. It amuses me to see the focal length in the EXIF say 300mm and then the lens identifier say I am using a 70-200mm lens.

As it has no impact on image quality I don't worry about it. In fact that lens delivers great image quality on the camera, way better than it should according to its reputation.

tl;dr: if it ain't broke, don't fix it.
07-22-2010, 07:28 PM   #6
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You can check the data the camera actually captured using the Review function in the camera.

This will rule out any possibility that the photo processing software on your PC side is wrongly reading the data.

Any problems with actual exposure ?

Focal length reading is required for correct SR functionality - so if the camera is misreading the focal length , your SR may not be compensating the right amount.

Pentax cameras often don't read Sigma lens EXIF data correctly, but basic things like Focal Length, Aperture are normally OK.
My K-7 can't differentiate between a 17-70mm/ 2.8- 4.2 and a 18-50mm f/2.8, but that's just the lens ID, no problem with more critical data.
07-22-2010, 07:41 PM   #7
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QuoteOriginally posted by Quicksand Quote
Are you sure there's nothing functionally wrong? Shake reduction uses the focal length to determine how much correction to apply, so if the lens is reporting that incorrectly, you may get bad results.
Got that covered, I actually use the OS built in all the time, so SR is disabled.

The exposure seems pretty much correct to me... nothing too out of the ordinary... the exposure *could* be f.5 off... but I'm not too sure... and it doesn't strike me as if it is.

And... uhhh... so far I've tried UFO RAW and Pentax software... both seem to be reading the exact same thing ;(.
07-23-2010, 12:32 AM   #8
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QuoteOriginally posted by NecroticSoldier Quote

While there is nothing adversely wrong about this lens, is EXIF data really important?
If it were me, I'd have it fixed if the camera really can't read the FL. If the camera is not reading the FL, then it is almost impossible that things are not going wrong somewhere that you don't know about. It is not just SR, but flashes that definitely need to know the FL, and there are probably a few other calculations that need to know what lens is attached.

As someone else said, if the issue is just whether the software you are using to look at EXIF has the Sigma in its database, that is a different story. There are programs that will let you look at the raw numbers coming out of the camera. I believe it was EXIFeditor (crude, but effective) which allowed me to see that some of my issues were just in the software reading the EXIF, and the numbers were changing.

07-23-2010, 09:08 AM   #9
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QuoteOriginally posted by GeneV Quote
If it were me, I'd have it fixed if the camera really can't read the FL. If the camera is not reading the FL, then it is almost impossible that things are not going wrong somewhere that you don't know about. It is not just SR, but flashes that definitely need to know the FL, and there are probably a few other calculations that need to know what lens is attached.

As someone else said, if the issue is just whether the software you are using to look at EXIF has the Sigma in its database, that is a different story. There are programs that will let you look at the raw numbers coming out of the camera. I believe it was EXIFeditor (crude, but effective) which allowed me to see that some of my issues were just in the software reading the EXIF, and the numbers were changing.
Yeah my flash reads focal length, that is why I was sorta worried.

Thanks, I'll try EXIFeditor and see how it goes.
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