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"32 bit HDR TIFF" -- "16 bit per channel TIFF" -- I'm confused.

turnstyle

Active Member
Joined
Jan 4, 2011
Messages
229
Hi all, I'm starting to experiment with combining several exposures to make one final exposure.

It might be a bracketed set in an HDR type scenario. Or it may be a series of nighttime long exposures, all stacked together to get star trails.

Given the talk about the not-yet-released Lightroom 6 -- I learned about what seems to be called a 32bit 'Pro HDR' TIFF -- I also see that when exporting a TIFF from Lightroom, I have the option of selecting 8 or 16 bits per channel.

Can somebody possibly help me understand the difference between a 32bit 'Pro HDR' TIFF (as in the Merge option) and a 8 or 16bit TIFF as exported by LR?

Here's why I ask:

1) I import all my RAW into LR

2) I make modest adjustments, such as ensuring they have the same White Balance

3) I export from LR -- here's why I'm interested in exporting as 16 bit rather than 8 bit per channel

4) I import those into an application that merges them -- either, say, HDR or star trails.

5) I export from that -- and here's why I'm interested in the 32bit 'Pro HDR' TIFF...

6) I import that back into LR and do more editing.

SO...

I want to maintain the best fidelity from LR, through the merging application, back into LR -- retaining the most detail and ability to adjust highlights and shadows.

I hope somebody here will understand what I'm talking about! :)

Thanks in advance, -Scott
 
Joined
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Hi Scott.

I do merge to panorama regularly and merge to HDR when needed.
Step 3 is wrong - do not make TIFF's for your merges.
Instead, if your copy of Lightroom and Photoshop/ACR are co-ordinated you can send the raw files instead.
If that is not possible then make DNG files instead.

In Photoshop once the merge to panorama is done bring a 16-bit TIFF back into Lightroom.
If you are doing a merge to HDR create a 32-bit TIFF to bring back into Lightroom.

Your concerns about quality are valid but I can tell you from experience that what you do in-camera is crucial to a good result.
Be prepared to make this a learning curve - it is highly unlikely that you will nail a final result on the first try.
Getting your technique correct in-camera is the first hurdle.
Once you have the technique in-camera there is a big post-processing learning curve, once the merges are done.
If you spend a lot of time on this after several months you will likely start getting good results.

If you need more help on this we can explore some more.

Tony Jay
 

turnstyle

Active Member
Joined
Jan 4, 2011
Messages
229
I'm not actually using Photoshop at this time, though I am thinking about it.

Right now I'm using an app called Pixelmator.

My first project has been star trails.

I set my camera to take series of 30-sec exposures over an hour.

And I bring them all in as layers in Pixelmator, and set all of them (except the bottom layer) to have a blending mode of "lighten" -- at which time my trails show up.

So wouldn't TIFF be preferable there? eg, I'm not so sure I would actually want Pixelmator developing from RAW/DNG, even if it can?

Also, there is some sort of high quality TIFF called 32bit Pro HDR -- that's a different kind of TIFF, is that correct?
 
Joined
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Messages
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Brisbane, Australia
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Lightroom Version
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I don't know Pixelmatr at all - no idea what its compatible file formats are.
As for a 32-bit TIFF, as far as I know Photoshop merge to HDR is the only process that produces it - again other apps that do HDR may produce a 32-bit TIFF but I am not aware of them.

Tony Jay
 

Michael D.

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Location
Hackensack, NJ
Lightroom Experience
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Lightroom Version
I don't know Pixelmatr at all - no idea what its compatible file formats are.
As for a 32-bit TIFF, as far as I know Photoshop merge to HDR is the only process that produces it - again other apps that do HDR may produce a 32-bit TIFF but I am not aware of them.

Tony Jay

My favorite software to create panoramas is PTGui and yes, it can create 32 bit TIFF files. Also, Photomatix Pro, an HDR program, can create 32-bit TIFF files. For their specialized applications, I find both programs superior to the Lightroom/Photoshop combo. There are free trials for both programs for those that are interested. (Disclaimer - I have nothing to do with either company other than using and liking their software.)
 

turnstyle

Active Member
Joined
Jan 4, 2011
Messages
229
Thanks, so I'm a bit confused by what these 32 bit TIFFs are -- when talking about a bitmap file, I would think 32 bit means 8 bits each for R, G, B, and another 8 bits for alpha -- so that's 32 bits total.

But these "Pro HDR 32 bit TIFFs" seem to be something other than that. For example, I gather you can combine multiple exposures into one 32 bit TIFF -- and wind up with much more room to recover highlights and shadows -- meaning, more fidelity is in the file.

On top of that, when I export from Lightroom, I can export TIFF as either 8 or 16 bit per channel. So if that file only contained R, G, B -- 16 x 3 = 48 bits (or, if alpha is also included, 64 bits?).

So here's what I'm confused by:

1) old-school bitmaps have long been 32 bit -- (R, G, B, A each getting 8 bits)

2) new high fidelity TIFF is referred to as 32 bit TIFF

3) exporting from Lightroom seems to let you export what seems to be 48 bit TIFF.

So can anybody explain? For example, is "32 bit TIFF" a new format? Is the 32 bit in that actually 32 bit *per channel* rather than *total*?

Thanks again to all, hopefully this is useful to other folks too...

-Scott
 
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