What is "highlight tone priority" good for anyway?

[Policar]

And if I understand it correctly, I can indeed simply reproduce this by shooting at iso 100 with 1ev underexposure and then apply a tone curve in postprocessing?!

Not sure if it would mimic the process 100%, especially since we don't know exactly what curve Canon uses, but it would probably be very, very similar and more flexible.  But yes, basically, highlight tone priority just turns down the ISO a stop then tags your images as being shot with it.

If your style requires clean shadow detail, expose to the right or use HDR.  If I ever shot landscapes digitally (I might some day!) I'd shoot 100ISO and expose to the right.  But for most of what I shoot (jpeg and video) it's fine for me.

[Bosman]

I recommend doing the research in Google. If you need more look it up.

I already knew and wrote what htp does, I've taken tenth of thousands of pictures with it. And I'm perfectly able to type something into google, but as you may or may not have discovered that not everything an internet search returns is very reliable. So I guessed it'd do no harm asking here if anyone has separated the usual user theories from the real information, no need for anybody to reply...

That being said, thanks for the links. But my question still is: If it's just an in-camera tone curve, why does it raise the iso value? Is it really 100% something that can be done in postprocessing?

Apologies for possibly offending you there brother. Perhaps I could have written that better.
Here is Chuck Westfalls info on some Canon Tech.
http://digitaljournalist.org/issue0902/tech-tips.html
"Highlight Tone Priority (HTP) is available with all current EOS models excluding the Rebel XS/1000D. HTP has no effect on the actual dynamic range of the image sensor. It's just an alternative method of image processing that preserves more highlight detail than Canon's standard processing, without significantly altering midtones or shadows. The effect of HTP is enhanced by Canon's 14-bit A/D converter, which provides finer tonal gradations than the previous 12-bit system. HTP is a Custom Function with a simple on/off setting, and the available range of ISO speed settings is slightly limited when it is on. Take a look at the following Web page for some sample images that show the capabilities of Highlight Tone Priority:
HTP affects RAW data as well as in-camera JPEGs. It is very useful in high-key shooting conditions such as wedding photography and certain kinds of sunsets. ALO can be combined with HTP with cameras that have both features."

[Marsu42]

Apologies for possibly offending you there brother. Perhaps I could have written that better.

:-) ... sure, no problem, and because my native language is "Sprechen Sie Deutsch?" I guess I'm often not expressing exactly what I've intended to...

without significantly altering midtones or shadows

This leads to the question: What's "significant"? Unfortunately, to me htp alters/compresses shadows so much that I've only used it in some situations lately, and now that I understand what it actually does in the camera might skip it completely.

HTP affects RAW data as well as in-camera JPEGs

This is exactly the statement I had - and which made me believe that "affect" does mean "alter" and not just "shoot at lower iso and then set a flag in the file apply a tone curve". I'm happy this is now clear to me :-)

ALO can be combined with HTP with cameras that have both features

... but of course alo really only affects jpeg. That's why my original question was about htp since it's very unusual that a body has a setting that affects raw data (because then it isn't "raw" anymore - but as we know raw files don't contain raw sensor data anyway).

[Bosman]

Basically, I don't need it but I have had some crazy backlit wedding portraits that killed some of the hair detail but rim light is something to enhance an image and giving up some detail is part of that equation. I havent had too many wedding dresses loose detail without HTP being on but that said there are a few but only in crazy light. I may have a few photos that would have benefitted from it but thats not enough to justify having it on for me.
If i did use it It would be in a case where there weren't a ton a shadowy areas to begin with then i wouldn't be giving up any detail info in the darker areas. I think snow-lit scenes and beach scenes may benefit the most. Does anyone else have thoughts on where they would use it?

[Policar]

The shadow noise it adds is so trivial, and would be 1000 times worse on color negative, once printed.  I use this for virtually everything I shoot during the day, but I don't shoot professionally.  To me the clipped highlights look a lot worse than a little shadow grain that is unnoticeable when printed.

I turn it off when shooting video at 3200 ISO or over or when shooting indoors at high ISOs.  Almost never shoot raw, though.

[Marsu42]

To me the clipped highlights look a lot worse than a little shadow grain that is unnoticeable when printed.

Of course clipped highlights are worse than shadow noise - the question is just if htp is not outperformed by shooting at half iso, underexposing 1ev (thus saving the highlights) and then raising the shadows with an intelligent algorithm like in LR4 in contrast to applying just a dumb tone curve in the raw converter...

[nikkito]

after reading all this i got confused. ha!
for those shooting Raw and using lightroom having HTP activated doesn't change anything. or am i getting all wrong?

[Marsu42]

after reading all this i got confused. ha!

You're correct: you're confused :-) ... but I'm sure Canon marketing wants people confused and thinking that htp is a mini-hdr mode (as I thought) or magically expands the dynamic range of the sensor. Fyi: htp changes the tone curve when shooting jpeg or raw. In jpeg the effect is applied in the camera, for raw as it seems from the discussion above in the raw converter (Canon dpp, Adobe raw).

[nikkito]

Wahrscheinlich ist es so wie du sagst 
I know it's not a mini HDR or something like that. What I'm asking myself now is if I can get the same results when i Post process a picture with Lightroom. Does it makes a difference if you have it on or not?

I used to have it on, not the same with ALO since I know that works only if you're shooting raw (or jpg) and post processing with DPP.

[adamkozlowski]

YMMV, but i used HTP for video. It enabled me to have a lot more detail in the highlights. And of course it's useful to all those "brave" people who shoot JPG.

[Mt Spokane Photography]

For those who are confused, The purpose of HTP (Highlight Tone Priority) is to prevent over exposure of highlights while still allowing you to view details in shadow areas.
 
It underexposes one stop, and the tone curve it uses for in camera jpegs lightens up darker areas so you can see a bit of the detail.  Its pretty subtle, so there is not a huge difference, but if you are sending out of camera jpegs straight to a printer or to the web, it may help.
 
You do not want to use it unless you have bright areas in a scens along with areas in the shade that will be too dark to see details when underexposed one stop.
 
 

[Marsu42]

[quote author=nikkito link=topic=5687.msg108886#msg108886 date=1334524131
What I'm asking myself now is if I can get the same results when i Post process a picture with Lightroom. Does it makes a difference if you have it on or not?
[/quote]

You cannot get around thinking while shooting :-) and looking at the histogram and search for clipped areas.

With a high contrast scene, it doesn't really matter if you underexpose manually or use htp - but imho you're more flexible when doing it yourself, because you can underexpose not just 1ev, but a little more or less because too much underexposure than necessary to save the highlights will introduce noise when re-raising the shadows in postprocessing.

[Bosman]

I recommend just using your histogram and another level past that the color histogram. This will ensure even your colors aren't clipped.