Highlight Tone Priority

[Jonathan Huyer]

Has anybody used this feature? I have previously just ignored the setting, but recently found out that it works with Raw images. So I'm keen to give it a try. Blown highlights are the most common exposure problem I have. https://www.youtube.com/watch?v=cbGW0yUUCcg

[neuroanatomist]

It depends on what you mean by 'works with RAW images'.

What HTP does is deliberately underexpose by one stop, and 'misrecord' the ISO in the metadata - that's why ISO 100 isn't available when you turn on HTP, i.e. you set ISO 200, it shoots at ISO 100 but records 200, or you set ISO 800, it shoots at 400 and records 800. If shooting JPG, it processes the underexposed image to brighten everything except the highlights (meaning it applies a tone curve). If shooting RAW, it sets a metadata flag so DPP can apply that tone curve.

If you open that RAW file in a 3rd party converter, results vary. Some ignore the flag and you just get an underexposed image. Others compensate by just boosting the total exposure by one stop. Of course, that just re-blows your highlights and adds shadow noise. AFAIK, no 3rd party converter tries to replicate the tone curve to preserve highlights.

So, if you shoot RAW and use a converter other than DPP, I'd leave HTP off so your reported ISO reflects the actual ISO used to take the shot, and just expose properly to preserve highlights. You can apply your own tone curve, not limited to the one full stop forced by HTP.

Personally, I don't use HTP for those reasons.

(Full disclosure, I didn’t watch the video but…‘Life-changing setting’. LOL)

[neuroanatomist]

One more note – if you’re using a reasonably new-ish camera (5DIV or later) and shooting at relatively low or even moderate ISOs and using a good RAW converter, there’s almost no noise penalty for lifting the shadows a couple of stops. Recent Canon sensors are ‘ISO invariant’ (Sony and Nikon have been that way longer) meaning it doesn’t matter if you raise the ISO in-camera or push the RAW file.

Practically, that means that if blown highlights are a major problem for you, you can just set your camera to –1 stop (more or less) of EC, or use AE microadjust if your camera has it, and push the shadows of your images in post.

[DavidEccleston]

Neuro, if the converter defaults to just boosting by a stop, and there's no real penalty to boosting shadows on modern sensors, doesn't that mean it gives you an extra stop of possible highlight recovery, essentially for free?

Manually ECing means you'd need to adjust each and every one your images back up a stop to get them normal, even if the highlights would not have blown, on the off chance if might save a rare shot. Using this feature would give you normal looking images by default, with the potential to claim back blown highlights during RAW conversion. That does seems useful, if not life-changing.

[neuroanatomist]

Neuro, if the converter defaults to just boosting by a stop, and there's no real penalty to boosting shadows on modern sensors, doesn't that mean it gives you an extra stop of possible highlight recovery, essentially for free?

Raising the exposure by a stop will just re-blow the highlights, you'd have to lift just the shadows to 'recover' the highlights.

Manually ECing means you'd need to adjust each and every one your images back up a stop to get them normal, even if the highlights would not have blown, on the off chance if might save a rare shot. Using this feature would give you normal looking images by default, with the potential to claim back blown highlights during RAW conversion. That does seems useful, if not life-changing.

If I was going to go that route, I'd just set a default profile that included a positive exposure adjustment of a magnitude matching the negative EC on the camera settings. No need to 'adjust each and every image' since they'd all be adjusted automatically for me, and if I wanted to recover blown highlights I could drop the exposure down and lift the shadows.

For me, this is a bygone issue. On a DSLR you had to take your best guess to expose for the highlights or chimp the exposure )maybe with 'blinkies' after the shot and reshoot (if you could). With mirrorless, you see the final exposure being captured in the viewfinder, you can even see a live histogram before you take the shot.

[DavidEccleston]

Raising the exposure by a stop will just re-blow the highlights, you'd have to lift just the shadows to 'recover' the highlights.

If Lightroom was raising the exposure by a stop, you'd get the same default look as a non HTP image, which is what you'll want 99% of the time... But you'd have more headroom to recover the highlight. Yes it would be blown by default when converted to JPEG if you ignore the blown highlight. I'd rather it do that than automatically attempt to recover blown highlights making each image an inconsistent exposure. The benefit is that with the highlight not blown in the RAW data, you have the option to recover the highlight in post.

I edited my post above to include an image of the 3 settings, when lowering the exposure to make the blown highlights at raw-level clear.

[DavidEccleston]

So, just tried it R7, Sigma 18-35, dim living room with stand-lights near walls.

Off: Lightroom shows ISO 3200.
D+: Lightroom shows ISO 2500.
D+2: Lightroom shows ISO 1600.

Image are progressively darker in Lightroom, so it's not applying a curve, or boosting exposure.

Setting D+ image to expose +0.4 looks the same as off. This can be setup easily as a preset.
Setting D+2 image to expose +1.0 looks the same as off. This can be setup easily as a preset.

Turning down exposure to see highlight clipping.


Off: Significant clipping.
D+: Clipping at brightest spot
D+2: No Clipping


HTPDimmed by Dave E, on Flickr

So, it does what it says on the tin. Would be nice if Lightroom could automatically apply a curve or simple default exposure adjustment.

[neuroanatomist]

At the end of the day, it’s just the camera underexposing the image and effectively not showing that in the selected ISO. If that helps you avoid blown highlights, go for it. Similarly, some people know they’re prone to being late, so they set all their clocks a few minutes ahead, so when think they’re running late they still end up on time. Personally, I prefer my clocks and my ISOs to be accurate.

[Jonathan Huyer]

Good feedback! Thanks for the insight. I'll give it a test and see how it goes, but I agree that with EVFs there's really no excuse for blowing things out anymore.

[DavidEccleston]

If you're expecting fast action when you don't have time to examine and adjust your settings, it could be useful, but no more useful than just setting EC to -1. In more carefully controlled shooting, yeah, not much value.

Think of it more as 'the camera can record more dynamic range than is usable... would you prefer to capture extra shadow detail that can be boosted, or extra highlight detail that can be brought down.'. Keep it normal if you're afraid of shadow details being lost, and use HTP (or just EC -1) in you're worried about highlights. The ideal option would be for HTP to act like EC -1 when shooting, but auto-boosted to normal in Lightroom... but since it doesn't do that, you might as well just use EC -1 to avoid the "fake ISO".

Maybe if Lightroom supported a tone curve going outside of 0-255 they'd have added one for HTP. Currently you have to use the lowered exposure and boost mids and shadows, or fix exposure to be normal then lower highlight and/or whites sliders, everything after that section seem to be done post-RAW conversion. Just adjusting curves still clips highlights even when they should be recoverable, you just get dimmer clipped values. I didn't know that before yesterday, so if nothing else, this discussion has helped there!