Be careful when evaluating focus in DPP

Started Oct 31, 2009 | Discussions thread
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Horshack
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Be careful when evaluating focus in DPP
Oct 31, 2009

Everyone who uses DPP knows about its rendering delay. When you open a raw image, esp. an 18/21 MP image, DPP first renders the photo in low-quality mode to quickly get it displayed. After the low-quality render is done, DPP then starts a high-quality render that takes a lot longer to complete (approx. 4 seconds on my Q6600 2.4ghz quad core 2 duo).

For focus tests I typically shoot a sequence of 5-10 photos and then load the photos into DPP. Last night I noticed DPP will not do a high-quality render for all photos when they're loaded in quick succession. After loading the first photo, DPP does the low-quality render and then starts the HQ render. If I then load 4 other photos while the first photo is doing the HQ render, DPP will not do the HQ render for the other 4 photos, even after arranging the photos (menu: Window -> Arrange Vertically) to all be visible at the same time. DPP will only do the HQ render for each subsequent photo if you click on that photo's window.

If you load the photos slower, so that you give DPP a few seconds between each, DPP will do the HQ render for each. So it appears DPP will only do the HQ render for an active window if there's not another HQ render in progress, otherwise DPP never does the HQ render for that active window if another window is subseuqently made active (DPP doesn't queue all the windows it needs to render). This results in only the first and last loaded photo being rendered HQ.

Here's how this can bite you...Inside DPP I arrange the windows/photos (menu: Window -> Arrange Vertically) so that all photos are visible at the same time and then zoom into my focus target in one of the photos. By default the windows are synchronized (menu: Window -> Synchronize) so that when I zoom to the focus target in one photo, all the other photos zoom into the same area as well. I then look at all the photos to see which are in focus and which aren't. However, because DPP never did the HQ render for the other photos they'll appear to be OOF when they're not.

Here's a sequence of screen shots to demonstrate this. What can really throw you off is DPP's "High Quality" status indicator in each of the opened windows - a reasonable person might conclude this indicator means the HQ render has been done when in fact it hasn't.

Here's what the photos look like after they've been loaded in quick succession at their initial magnification (which is "Fit to Window") and then arranging them and switching to 100% magnification. The "active" window is IMG_0038, which was the first photo loaded. Notice that IMG_0039 appears OOF.

Here's me clicking on the IMG_0039 window. DPP displays the "Generating a high-quality preview" message in the status bar.

When the HQ render is done, IMG_0039 no longer appears OOF.

And here's the same thing for IMG_0040. First I click on the window to start the HQ render.

And now IMG_0040 is in focus.

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Kodak Instant Camera
Kyocera 1MP Camera phone (pre-paid phone plan)
http://horshack.smugmug.com/

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