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Old Dec 20, 2005, 11:36 PM   #1
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I just downloaded DxO for the 20D and the 17 -85 lens. It seems to be very easy for jpegs, but when I tried it on Raw files it asked for focus distances on each one. While this is not difficult for a few pics, itis a fairly daunting task to batch edit a bunch of photo's having to enter the focus distance manually for each one!! Does anyone have a comment on this?? The program does a nice job of pre-Photoshop lens corrections and I think would improve the quality of photo's that I can achieve. Just wondering why it can't get the focus distance from the EXIF data??

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Old Dec 21, 2005, 1:55 AM   #2
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Because Canon stopped writing the focusing distance into the EXIF data.

They used to do it on the 10D and 300D, but later models don't. The reason presumably is that programs like DXO can make the photos from the 17-85 essentially indistinguishable from those with far more expensive L lenses. I think they're shooting themselves in the foot with that decisition though.

At any rate not having the focus distance affects only 2/10? corrections that DXO performs. Lateral CA and distortion.

So if the conditions are not such that you need to worry about Lateral CA and distortion then you need not bother, by default in fully automatic mode it will assume that the focus point was infinity.

Also note that it depends on the lens you are using and I think that the focusing distance is not even asked for on most telephoto lenses. Certainly it doesn't need to know on the 70-300 DO.

In any event, unless you have a VERY fast computer I would suggest that you probably don't want to be running every image through DXO, select your keepers first and then process them. That makes entering focusing distance much less of a chore.

Do make sure you set your output type appropriately, I am currently exporting to TIF, but it is tempting to consider using DNG as an output type. The only reason I could see for using JPG output is if you want to resize the image downwards at the same time, or perhaps if you plan on sending a large batch of snaps to the printers.

I am a complete convert to DXO. Essentially it does just about everything I would normally do in PS except a final levels adjustment and output sharpening. It saves me on average 30 minutes per shot compared to doing it manually in PS.

Finally I guess I should say that even if you do have to manually input the focusing distance on each shot it takes no more than 2-5 seconds per shot, and so adds perhaps 5-10 minutes to a fairly large batch but doing corrections in PS for CA and distortion takes a lot longer than that, because if you're doing it to the same standard as DXO you need to be looking at the photo and adjusting according to the focusing distance anyway, no? Actually for me no, because I wouldn't have a clue as to the details of the profiling algorithm they use, so correcting CA and distortion for me in PS is a far more subjective matter based on what looks right on screen, and that takes a lot longer than simply entering the focusing distance and letting DXO take care of it. Still a big advantage to DXO.

One possibility is to run the batch without entering focusing distance and then if you notice distortion or CA problems on a particular shot then go back and re-process it after manually setting focusing distance.

If you fancy starting a petition to get Canon to write the focusing distance back into the EXIF data I'd be happy to sign it. :-)
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Old Dec 21, 2005, 4:18 AM   #3
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Peripatetic (or bigboyhf) ... Can I ask a (maybe stupid) question relating to this?

I was wondering, is focus distance DIFFERENT to focal length? I'm assuming so, because Iknow what focal length is (the amount of zoom you're using).

So is focus distance the "centre" of the DOF area? (where the lens FOCUSES?)

My Canon 350D (1 month old) shows focal length in the EXIF data, but not focus distance.

If you could clarify this... thanks!

Safe n happy Christmas

PJ
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Old Dec 21, 2005, 5:07 AM   #4
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Yes that's right. Did you focus on a subject 1m or 10m or 100m distant?

To correct for certain kinds of distortion the DXO program needs that information.
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Old Dec 21, 2005, 8:08 AM   #5
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Wow, that's really crappy that Canon disabled that in the EXIF data. I just assumed all body/lens combos needed manual focus distance settings.
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Old Dec 21, 2005, 12:02 PM   #6
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Threequestions...

If I have 150 shots to process and I choose 10 as keepers, how am I supposed to remember what the focusing distance was for each?? When I did 5 shots, on manual, the batch would not even process without that info. Auto would though...

Why would DNG be better than TIFF?

Do you use Auto over expert all the time, and if so, does the Auto setting correct all the same settings?

From the few pics that I fixed with DxO, I was very impressed with the results.

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Old Dec 21, 2005, 12:15 PM   #7
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Well I find that if I look at the image I can get a pretty good idea of the focus distance. The harder it is to tell the distance the less it probably matters. In general it's only really important at the wider angles and with close focus distances, otherwise setting it to something approximating the hyperfocal distance or at infinity works fine.

DNG v TIFF - well only that you then get a chance to work on a "RAW" file when you import it into PS. I've never done it so I don't know if there's any mileage to be had from that method. It just occurred to me that there might be.

I have it set on Expert most of the time.
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