Highlight Tone Priority-always leave off or...?

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eco_bach

Well-known member
A lot of DSLR experts suggest leaving this off, but in a few instances I've read its best to leave it on, for daylight shooting at least.
My understanding is that the net result of this feature is that it underexposes just your highlights by one stop, thus preserving detail.
So wouldn't it make sense to leave this enabled for all daytime shooting?
Any thoughts?
 
Makes your mids and blacks quite noisy in interiors or low contrast environments. I leave it off all the time unless it really helps a shot out.
 
I like the noise it adds, and it recovers a stop of highlights, so horses for courses I suppose.
I used it at iso 1250 for the short linked below my signature.
 
eco_bach said:
My understanding is that the net result of this feature is that it underexposes just your highlights by one stop, thus preserving detail.
Click to expand...
It underexposes everything by one stop. It cuts your ISO in half. It then uses 6dB of gain on the midtones and shadows to bring them back up to where they would have been, had you not been using HTP in the first place. That's why the mids and shadows get noisy.

It is appropriately named -- it places the priority on the highlights, hence Highlight Tone Priority. It's not magical though, it gets there by underexposing your mids and shadows.
 
Barry_Green said:
It underexposes everything by one stop. It cuts your ISO in half. It then uses 6dB of gain on the midtones and shadows to bring them back up to where they would have been, had you not been using HTP in the first place. That's why the mids and shadows get noisy.

It is appropriately named -- it places the priority on the highlights, hence Highlight Tone Priority. It's not magical though, it gets there by underexposing your mids and shadows.
Click to expand...

I'm glad I didn't read this before experimenting, it sounds like a terrible idea, though in practice I use it frequently : )
Thanks Barry for the explanation, no sarcasm intended.
 
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I don't think it's a bad thing at all. It's perfectly appropriate for certain scenarios, daylight being one of the primary intended uses. You just have to know what it does. It's along the same lines as Panasonic's DRS, except that DRS dynamically evaluates the whole frame and acts only on certain areas, whereas HTP acts on the whole frame globally. But hey, if you need it, use it -- and certainly its most desired usage would be in daylight scenes. But, just like DRS, I wouldn't advise leaving it on blindly, because it does have side effects (shadow and midtone noise). It's just another tool in the toolbox, not a magic fix-all, and when you need it, it's nice to know it's there.
 
Yes thanks Barry that's always been a mystery to me. Doesn't sound to attractive though.

Actually here's a question - Does it actually salvage any info that would be lost in shadows or does it merely raise what is there to a higher level?
If it doesn't save any information I'd rather do it in post where i have the choice.

lenny Levy
 
Sorry for the amateur question, but what does it mean to "cut the iso in half"? I suppose it doesn't mean that iso 800 becomes 400, but I can't figure out what that means?
 
Adding 6dB of gain to the mids and shadows can salvage info, albeit with noise.

Cutting the ISO in half lowers the exposure by one stop. It does mean 800 becomes 400. And that's why 100 is not a choice in HTP mode.
 
I seem to recall hearing that there was artifacting associated with it - is that true..

Thinking more on it , if you're outside with low ISO's anyway the increase in noise might not be a big issue at all. If it does this seamlessly it might be a great tool.

Lenny levy
 
That's the way I look at it -- if you need it, go ahead and use it.

I don't know of any artifacts associated with it, other than increased noise due to the system gaining up the shadows and mids. I think the only danger with HTP is in those that think that they should use it always; it's a special-case thing where you should use it when it's appropriate, and only when it's appropriate.

With DRS there can be some artifacts if you push it to level 2 or 3, but DRS is working on almost every pixel individually and dynamically adjusting all the time. HTP isn't really like that, it's (as I understand) a much simpler function; it just chops the ISO in half (so, yes, if you set it at ISO 800, it would be exposing at ISO 400) and then re-gains up the shadows and mids.

Does that mean something might be lost? Definitely. If something is so dark that it's on the very bottom of the exposure curve, and you stop down a stop, then yes that lowest-lit information would be crushed off to black, and adding gain to it won't restore it. But it's only the stuff that would be within one stop of being lost anyway. And you do gain a stop in the highlights so -- it's not really necessarily lost, just -- well, moved. If you put HTP on it will lower the exposure by a stop; if you then gain up a stop you'd have all the exposure you would have had in the first place -- except now with noisier shadows. So really, it's a case of you only use it when you need to save the skies or the highlights and you are okay with what happens to the shadows; and in that way, I think it's very appropriately named. It's for when you prioritize your highlights.
 
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