EOS R6 Mark II: Help Needed Exploring use of Highlight Priority

[Skip70]

I'm leaning into using the Highlight Priority feature now that I learn it works in RAW without reformatting my photos to jpeg. 

A few questions for the expert community:

1. I'm puzzled that it changes the minimum ISO to 200. Why that? 

2. In exposing for the highlights, do I still need to select a metering mode and target my exposure on a highlight area or does the camera automatically sense highlights in the total frame and adjust accordingly? If I do the former, it seems I am exposing for highlight anyway, thus obviating any need for an inc-camera program to adjust to avoid blown highlights. If the later, am I correct that I just exposure for the subject of my shot and trust the program will adjust for any highlights outside of the dynamic range?

Thanks for any help on this.

1.  

[kvbarkley]

"I'm puzzled that it changes the minimum ISO to 200. Why that?"

I read an article about this many moons ago, so I can't find it, but IIRC, HTP changes to slope of the tone curve, and because of that, it needs some "headroom" (tailroom?) at the low ISO end.

[jrhoffman75 · Accepted solution]

https://www.eos-magazine.com/articles/eospedia/what-is/highlight-tone-priority.html

[Skip70]

Excellent, thank you. All one could ever want to know about HTP (and I did read it all!). 

Wish I had known this when I was taking photos las month of white egrets!  

[Peter]

"1. I'm puzzled that it changes the minimum ISO to 200. Why that?"

Because, in terms of raw data, ISO 200 HTP is the same as ISO 100. If you use the same shutter speed and aperture, the raw image data in the file will be identical whether you shoot at ISO 100 or ISO 200 HTP.
Open the raw files in software that doesn’t read the Makernote tag for Highlight Tone Priority, and you’ll see what I mean.

[johnrmoyer]

If your camera is set to save a raw file, then in the Canon DPP software, https://cam.start.canon/en/S002/manual/html/UG-04_EditImage_0040.html#EditImage_0050_11 one can make small adjustments to dynamic range. To me this seems better than highlight tone priority. 

Else, use negative exposure compensation. This will do approximately the same thing as highlight tone priority so at ISO 100 the image will be darkened as it would have been at ISO 200 using highlight tone priority.

If there is too much dynamic range in the scene, it is possible to use both negative exposure compensation and DPP to extend the dynamic range. 

Auto exposure will often expose for highlights if the subject is backlit and is small, or expose for shadows if the subject is small and in sunlight. Using exposure compensation to get the most detail on the portion of the scene that is important to the photographer seems like the best strategy to me.

The importance of darkening the exposure is that each of the R G B color channels clips at a different level and if the highlights are exposed so that they clip in the raw data, then white will change to another color or detail will be lost.

For example, the Cardinal in this photo was in bright sunlight and the red channel would clip with auto exposure. The shady background was not important to me. I used both negative exposure compensation and nearly the maximum dynamic range increase that could be done by DPP to get the feather details. https://www.rsok.com/~jrm/2026May11_birds_and_cats/IMG_5863c_2026may09_cardinal.html   

Northern Cardinal (Cardinalis cardinalis) in Norman, Oklahoma, United States on May 9, 2026

Edits done in DPP and saved to a dr4 file as a recipe

ExifTool	ExifToolVersion	13.25
File:Other	FileName	IMG_5863.dr4
CanonVRD:Image	WhiteBalanceAdj	Daylight
CanonVRD:Image	GammaShadow	0
CanonVRD:Image	GammaHighlight	0
CanonVRD:Image	GammaBlackPoint	+0.000
CanonVRD:Image	GammaWhitePoint	+1.990
CanonVRD:Image	GammaMidPoint	+0.000
CanonVRD:Image	GammaCurveOutputRange	0 16383

Camera Model Name	Canon EOS R5
Lens Model	EF100-400mm f/4.5-5.6L IS II USM +1.4x III
Focal Length	560 mm
Exposure Time	1/500
ISO	500
F Number	8.0
Camera Temperature	37 C
Measured EV	12.12
Measured EV 2	21.5
Focus Distance Upper	9.04 m
Focus Distance Lower	7.87 m
MakerNotes:Image	ExposureCompensation	-2/3