Is the new DNG "fast load" actually faster?

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turnstyle

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Hi all,

So far, I've been keeping my camera RAW files in the camera-specific RAW format.

But I'm interested in some of the new DNG features, and so I'm considering converting my camera-specific RAW files into DNG.

Is the new DNG "fast load" actually noticeably faster? What exactly does it speed up, and by how much? It is "noticeable"?

I'm also tempted to use the lossy compression for all the not-so-great pictures that I can't quite throw away.

(It would also be nice to be able to update the embedded preview, which I can't do with my camera-specific RAW file.)

Last time I considered switching to DNG, it didn't seem necessary -- but it's getting more tempting...

Thanks for any thoughts!
 
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The Fast Load data helps speed up the initial load of the image in the Develop Module. It doesn't help with anything else. And I haven't noticed any speed up with it. For me, it's snappy, anyway.

DNGs keep adding advantages. A nice one is the newish internal checksum that gives a warning when the data has become corrupted. Eric Chan on the Adobe forum describes DNG as a wrapper that can enclose any of the filetypes that LR handles, including JPEGs. JPEGs have their data simply copied into the DNG without a decompression-recompression step that would lose data.

Personally, I'm thinking strongly of converting my collection to DNG, many of which would be lossy-compressed.

Regarding lossy DNGs, produce a few, get a friend to re-name both them and their parents randomly and see how well you do telling them a part in a "blind" test. :)

Hal
 

turnstyle

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For the bulk of my photos, I don't mind a bit of lossy compression -- the big plus (for me) of RAW is the ability to fix white balance, recover highlights, etc. If I can still do all that with lossy DNG files, then that's good enough for most of my pics -- seems to combine the advantages of RAW and JPG.

So Fast Load does make it snappier if you're flipping though your catalog? For example, for non-cached files? And for cached files too? ie, will I see less "Loading..."?
 
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No, I said I didn't notice a difference. I've got a snappy computer, so the loading bezel flashes on and off very quickly, anyway. I'd be interested to hear how it goes for you in a test.

Hal
 
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Imagine that fast load data as removing the need for the ACR cache - which holds partially processed data. The first time you look at a DNG without fast load data, it has to read the full data, do initial processing, and then store that in the ACR cache. Future times it reads the ACR cache first so it's quicker. If that rolls out of the ACR cache before you next come to it though, it has to start again. Fast load data, on the other hand, is stored in the file, so it only has to do it that the first time round and in future it only reads it. The bigger or more complicated the file (certain sensors, certain opcodes like forced lens corrections), the greater the advantage.
 

turnstyle

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Since you mentioned lens corrections -- does that mean the fast load data within the DNG file itself will change if something like a lens correction is enabled/disabled?

btw, do you happen to know of any videos/web pages that specifically demonstrate these new features of DNG?
 
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Nope, the opcodes are for things like some Panasonic cameras which insist on their lens corrections being applied - you can't turn them off and they're performed much earlier in the pipeline. It doesn't apply to LR's lens corrections.

I haven't seen much on the new DNG stuff yet. It's on my to do list but the last week's been insanely busy, so it might not get done until the final release is out, although I'll try to get it done in the meantime.
 
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I'm pretty sure that Victoria was referring to some of the more recent point-an-shoot cameras that do lens corrections in software for their JPEGs. Raw converters (including LR) automatically do that lens correction when they render the raw file. You don't have to ask for it. That's what would be sped up by the fast-load data.

There are a couple of videos, one with Julianne Kost on Adobe TV and one on Lynda.com that talk about the new DNG features:
http://www.lynda.com/Lightroom-4-tutorials/Photoshop-Beta-Preview/96215-2.html
http://tv.adobe.com/show/whats-new-in-lightroom-4-beta/

Actually, all those videos in those series are worth watching.

Hal
 

turnstyle

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Thanks, I hadn't known about those Lynda videos. It didn't actually seem to show Fast Load Data making anything faster -- and another detail that struck me: it appeared that using Lossy DNG might slow things down. In any case, I'm glad to see DNG progressing.
 
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If lossy DNG slows things down, it won't be by much. Essentially, lossy DNGs are JPEG-compressed, and decompression of a JPEG seems blindingly fast on any modern hardware.

Hal
 

turnstyle

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That may be a beta bug.
 

turnstyle

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That may be a beta bug.

It'll be interesting to find out -- I'll be tempted to use the lossy option for some of my photos -- but if it takes noticeably longer to open them, I'm not so sure I'd bother.

And if anybody does find a video (or any other info) that demonstrates the real-world benefit of Quick Load Data, please do post!
 
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I converted a folder's worth of images to lossy DNGs with the fast-load option. The size on disk went from 615 MB to 241 MB, which is a sizable reduction, indeed. Going from one to the next in the Develop Module seemed to be neither faster nor slower than in a folder with unconverted NEFs. In all cases, the "Loading" message appeared for somewhere around half a second.

Hal
 

turnstyle

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Great info, thanks! fwiw, that came out to a bit less compression than I had expected (I thought it would be closer to 1/4 the original).

If you're in a testing mood, I'd be interested to know if fast-load, non-lossy DNGs actually seem faster than traditional DNGs -- in this case, Adobe describes them as 8 times faster, so it seems that should be noticeable.

Thanks again. :hail:
 
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Yes, they are faster. Maybe twice as fast. If I had a slower computer, I'd have a chance to do better timings, but having quick-load definitely makes a difference, at least when the images aren't in the Camera Raw cache.

Hal
 

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Lossy DNG

Anyone tried converting existing DNGs to the lossy format.
If I try the lossy option is greyed out so I assume I cannot convert which seems a bit of a pain.
Maybe I'm not setting things up right or it can only be done on import
 
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watsonm,

That's a bug that has been reported at the Adobe site. Sometimes it's greyed out, and sometimes not. I've managed to get it to work, although earlier in the same session, it wouldn't.

Hal
 

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Well I tried on my laptop and it worked. So went back to Main machine and when I tried again I noticed the pop up panel had the previous Camera Raw settings of 5.4 . I flipped it to 6.6 and the "use lossy Compression" check box "Ungreyed" itself. I selected OK and it worked.

Next experiment was to
Select several images in the film strip and do the same but it would only convert one image.
Selected them in the grid view and it converted them all.
 
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watsonm

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I'll cut and paste a reply I made in flickr:

"I tried it tonight. I reduced three images I use to make an HDR snap to lossy DNG. I then selected them and exported them to Photomatix.
On re import I could not tell the difference bewteen the two shots either at initial re import or if I synched the post processing. That was at 4:1. Not a conclusive test I know but seeing I do a lot of landscape HDR it was relevant to me.

Better test would probably be a couple of A3 prints from a complete file before and after conversion"

As a subjective test I didn't notice any major performance difference in selecting a lossy or lossless DNG in lightroom and from the screen could not see any difference between images either. So for non critical stuff I suspect I may move over when the final release comes along. But then I am just an amateur that only prints up to A3 for personal use.
 
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If you've got Photoshop Mike, try opening the original and lossy DNG in PS and putting them as layers on top of each other. Then change the blend mode at the top of the layers panel to Difference mode, and you can see exactly what the difference is. On the ones I tried, I was surprised to see how little difference there was, even at 100% view.
 

turnstyle

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If you've got Photoshop Mike, try opening the original and lossy DNG in PS and putting them as layers on top of each other. Then change the blend mode at the top of the layers panel to Difference mode, and you can see exactly what the difference is. On the ones I tried, I was surprised to see how little difference there was, even at 100% view.

hah, I used to do that -- fwiw, I'd also use the magic wand with tolerance set to zero -- that can give a nifty visual showing how the compression is applied.
 
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