What is Mac OSX Quick look doing to 14bit Nikon raw files?

[Andrew Reid]

 

Banding alert!

 

This is when you hit space bar to preview a NEF raw file from the D600, you get a low-res / low quality quick preview of the file. I'm not bothered by it (it is expected behaviour) but I find it interesting on a technical level.

 

What causes the banding?

 

For reference here is how Adobe Camera Raw handles the same 14bit raw file when it is opened in Photoshop CC.

 

[jgharding]

I've noticed this when using OSX with raw, it must use some kind of cheap and cheerful fast debayering to do previews. Windows just doesn't preview them at all!

 

It's lower in detail and has odd development, but I suppose it's just for a quick preview

[Quirky]

Banding alert!

 

This is when you hit space bar to preview a NEF raw file from the D600, you get a low-res / low quality quick preview of the file. I'm not bothered by it (it is expected behaviour) but I find it interesting on a technical level.

 

What causes the banding?

 

To answer the question in the topic title, the Quick Look is doing nothing to the image. It's merely reading the preview file Nikon have embedded in their proprietary RAW files. It does not open the actual RAW file. 

 

What's causing the banding, I don't actually know for sure, but my more or less educated guess is that it has something to do with the quality of the embedded preview file. Want a better looking preview, ask Nikon to cook one.

 

For reference here is how Adobe Camera Raw handles the same 14bit raw file when it is opened in Photoshop CC.

 

Well, opening the file in ACR/PS CC means that you're reading and converting the actual RAW file, not just the embedded preview, which Quick Look is using. 

[Andrew Reid]

Are you sure Quick Look is using the embedded preview? I thought this was an extremely low res thumbnail. Detail level is actually very nice on 27" iMac screen with Quick Look.

[Damphousse]

 

It's lower in detail and has odd development, but I suppose it's just for a quick preview

 

Not sure if I'm passing along new information here but if you want to view raw files in Windows you need a camera codec.  Here is the link for Windows 7.

[Quirky]

Are you sure Quick Look is using the embedded preview? I thought this was an extremely low res thumbnail. Detail level is actually very nice on 27" iMac screen with Quick Look.

 

I'm not 100% sure, but pretty sure, anyway. Feel free to prove me wrong, because I can't do that right now.

 

Looks like the "thumbnail" is actually a full pixel jpeg file. Or at least a rather large one. The same used by the lcd screen of your camera for a preview, which you can zoom into. Quick Look is using it, as long as it can read it. I don't have any NEF files, but my .ARW and especially my .DNG files look pretty good in preview, too. But they do look different (better) when opened up in, say, Aperture or another RAW converter.

 

Sometimes we can even see the preview of a yet unsupported RAW file of some new camera model, too, even though the RAW itself wouldn't open yet. Have you ever noticed that?

 

I believe it's up to each carrier package, and the metadata in it. Most RAW files do have an embedded full pixel jpg file cooked by the camera. But in some rare cases, like with the three-layer X3F files the embedded jpg image doesn't work with quick preview, even though it shows up and is zoomable in the camera screen. Why is that, I don't know yet. But it's there, and it opens up with the SPP app provided. Then it gets replaced by the actual processed RAW file, after a few seconds.

 

Apparently some preview files just aren't as well cooked as some others, or the metadata isn't optimised for the preview app, even though there's nothing wrong with the actual RAW file itself.

Just my 2c.

[jgharding]

Not sure if I'm passing along new information here but if you want to view raw files in Windows you need a camera codec.  Here is the link for Windows 7.

 

I didn't know that! Brilliant, thank you!