Examples showing HTP working with RAW files - 5D III

[Invertalon]

In the Dpreview review, they claimed that HTP (highlight tone priority) also benefits the RAW files. The general consensus is that it only benefited JPEG's, but that looks to be proven incorrect.

I took a series of sample images to compare side by side. Here are a few examples:

First one... This was AFTER I applied -100 whites and -100 recovery in LR4. Left side is HTP on, right is HTP off.


Untitled-1 by invertalon, on Flickr


Here is a second example. This is the RAW images, unaltered. Tripod mounted, live-view focused and manual mode taken within seconds of each other.


1 by invertalon, on Flickr


Now this after I applied -100 whites and -100 recovery. You can see some more detail retained on the left (on) side.


2 by invertalon, on Flickr

Finally, another area of the picture above on a blown out white house. This is after recovery of -100 whites and highlights. You can see more detail in the ON side.


3 by invertalon, on Flickr


So as you can see, HTP is giving more highlight headroom as Dpreview has claimed. No longer just for RAW files!

 

[Z]

As far as I'm aware, HTP has always worked for raw files. Are you sure you're not confusing it with auto lighting optimizer?

It's essentially shooting 1 ISO stop lower then applying a selective curve to boost the shadows/midtones, thus giving you an extra stop of highlight wiggle room - or at least this is how I've always understood it. The data is 'baked' into the raw file, but you'd be just as well off underexposing and applying your own curve adjustment in post. The result is increased shadow noise.

Someone correct me if I'm wrong.

 

[Invertalon]

Thanks for the info! I always thought HTP and ALO only benefited the JPEG's.

 

[mws]

I always thought it was only for jpegs.

Doesn't it take longer to buffer, slowing down the FPS?

 

[Invertalon]

I had comments on other forums that HTP increases shadow noise due to how it works. I looked in my examples in deep shadows and this appears to be correct. So if you prefer cleaner shadows, it may be best to turn off.

I turned off mine after seeing that. I would rather have cleaner shadows myself. Highlights have not been a big deal for me to save.

 

[Loswr]

As far as I'm aware, HTP has always worked for raw files. Are you sure you're not confusing it with auto lighting optimizer?

It's essentially shooting 1 ISO stop lower then applying a selective curve to boost the shadows/midtones, thus giving you an extra stop of highlight wiggle room - or at least this is how I've always understood it. The data is 'baked' into the raw file, but you'd be just as well off underexposing and applying your own curve adjustment in post. The result is increased shadow noise.

Someone correct me if I'm wrong.

Correcting you.

The HTP processing is not 'baked into the RAW file'. You're correct about what it does - reducing the ISO by one stop, then applying a tone curve to selectively push (meaning 'highlight preservation' at the cost of more shadow noise). The only thing baked into the RAW file is the one-stop of underexposure (which, I presume, is what Chuck Westfall meant when he stated that HTP affects the RAW image). In the metadata, the selected ISO is recorded (which is different than the ISO actually used), and the HTP flag is set.

When you open in the image in most RAW converters, the converter sees the flag and applies a tone curve to boost the exposure. Canon's DPP applies the same tone curve used in-camera. LR (ACR) uses Adobe's interpretation of that tone curve. The fact that you see a difference when you push the resulting images in your test is no surprise - you're comparing an exposure change in post added to Adobe's interpretation of the selective tone curve when HTP was used.

If you open an HTP-shot image in a RAW converter that doesn't support Canon's HTP flag, you'll just see a darker image - that same one-stop of underexposure that's the only effect on the RAW image data itself. That one-stop reduction does mean better preservation of the highlights, but you caould achieve the same preservation by applying a -1 EC before the shot. It's just that HTP may appear to do a better job, because it's using a complex tone curve that's difficult to manually create.

 

[nikkito]

i'm not the cientific guy like many of you here but if i take raw photos with HTP on (using Lightroom or using DPP), i can recover much more information from the highlights than when it's off.

And that's the important thing i guess

 

[Tcapp]

If HTP reduces the iso by a stop, does that theoretically mean that we can shoot at iso 25? Set it to L (iso 50) and use HTP? If it works as you all say it does, shouldn't it be possible to make it work for us as iso 25? (just curious if it would work / be an effective tool. No intentions of actually doing it!)

 

[Loswr]

If HTP reduces the iso by a stop, does that theoretically mean that we can shoot at iso 25? Set it to L (iso 50) and use HTP? If it works as you all say it does, shouldn't it be possible to make it work for us as iso 25? (just curious if it would work / be an effective tool. No intentions of actually doing it!)

No - when you enable HTP, the lowest ISO the camera allows you to select is ISO 200 (shot at ISO 100).

 

[Marsu42]

It's just that HTP may appear to do a better job, because it's using a complex tone curve that's difficult to manually create.

Did someone actually try and failed? It may involve some try & error but doesn't seem that impossible to come up with a point curve in Lightroom that emulates htp, or do the raw converters have some hidden magic unknown to the simple folk?

 

[Tcapp]

If HTP reduces the iso by a stop, does that theoretically mean that we can shoot at iso 25? Set it to L (iso 50) and use HTP? If it works as you all say it does, shouldn't it be possible to make it work for us as iso 25? (just curious if it would work / be an effective tool. No intentions of actually doing it!)

No - when you enable HTP, the lowest ISO the camera allows you to select is ISO 200 (shot at ISO 100).

Ah! Gotcha.