Do you use either ALO or HTP?

I have researched this topic, and still am a bit confused.  I understand how they work, and how both can improve the detail in under and/or over exposed areas, but I'm still not sure if there is any real advantage or disadvantage with either option.  I am shooting jpeg right now.

On my T6S, I have been trying ALO for a while and have not seen any dramatic changes in Jpeg  output.  I just enabled HTP in the custom menu to give that a try.  First thing I noticed was that the ALO option is now greyed out, so these apparently do not work together on this camera.  I was aware of the minimum ISO value of 200 now being the lowest level.  Still have not seen any real difference between this, the ALO, and standard shooting in the P, AV, or TV modes I typically use.

Does anyone have any real world experiences that they can share?  My inclination is to leave HTP enabled, but not really sure I'm on solid ground here.

I tried HTP and didn't seen enough if any difference. Decided it wasn't worth giving up ISO 100 for. Never tried ALO.

HTP basically meters an ISO step higher then applies a tone curve to compensate the image brightness. In other words, if the meter on standard settings would give you f/8 and 1/250 at ISO 100, HTP will meter f/8 and 1/500 at ISO 200 (or f/11 at 1/250, or any other equivalent combination depending on which mode you're in), then the camera processes the raw data at ISO 100 and lightens the image so the overall brightness is similar to the ISO 100 shot.

The way I see it, it's there to apply -1 step of exposure compensation (EC) for people who don't want to do that themselves. Guess what I'm gunna say next...

Yes, learn how to read your histogram and how to compensate the image brightness with the EC function. A lot of people think EC is a calibration setting (do it once and leave it alone forever), but it's a per-shot setting - take a shot, check the histogram and blinkies, change the image brightness if required and repeat until satisfied. Turn off all those "helper" functions (like ALO). Your camera will shoot faster and not get in the way when you're trying to take control.

As soon as you're ready, shoot raw and be amazed by what you can do.

Hi Stan, there can be a huge difference in highlight details being preserved if you shoot with HTP turned on. I leave it on by default and it blows my mind at times. Coincidentally, I did some testing today, hence why I am responding to your post.

For over a year I have left HTP on by default and I turned it on the day I bought a Canon 80D. I have always been blown away by the latitude of this camera's files in recovering shadows and highlights with raw files. I assumed the camera had a massive DR going by the amount of details I could capture/recover. For example, I have captured a white/grey seagull in the harsh Australian midday summer sun casting a harsh solid-black shadow onto the concrete pillar it was sitting on. I was able to recover details in the brightest white feathers while also recovering full details of the texture of the concrete pillar in black shadow. I could even overexpose the shadowed area.

I read an article saying it was just processing trickery which could be manually applied to the raw file in software, so I shot a whole event yesterday with HTP turned off. I did this to avoid adding any additional noise in the shadows which HTP can cause at times. I was horrified. For the first time ever since buying the camera I was finding I could not recover highlight details that would have been a piece of cake with HTP turned on. Those highlights would have simply been there already if shot with HTP on. It is winter here now and the contrast is nowhere near as high as on a bright summer day with a clear sky.

I did some test shots with a tripod capturing identical images with HTP on and off. In the most extreme my cat was lying on top of a chair with her front paws on a window ledge in the direct sunlight. I exposed for the cat which was in shade in the room. With HTP on the cat was correctly exposed, the windows ledge and cat's paws were overexposed, but still showed full detail. I could darken the highlights to taste, but detail was already evident without any adjustment. The shot with HTP off had the cat correctly exposed and the window ledge and cat's paws were blown out beyond recovery. I moved the Highlight Recovery slider to -3 (max recovery) in DPP and still had less detail than the unedited HTP image SOOC. Because I shot at ISO 200 there barely any difference in noise in the shadow areas of the image. There were some shadows on the window ledge cast by the vertical blinds. These shadows didn't exist in the image shot with HTP off as they were burnt out with most of the rest of the window ledge. The shadows were clearly visible in the unedited image with HTP on and looked true to the real scene when I applied some highlight recovery.

If you shoot in fairly flat lighting conditions there is probably no need to turn HTP on and restrict yourself from being able to select ISO 100. However, if you shoot outdoors in less than ideal situations, such as midday sun, then it is a no-brainer. Turn on HTP and preserve more highlight details than you could possibly recover using any means of software recovery later. I do have a Canon T6S (760D) too amongst several other cameras. I'll do some testing when I get a chance with that camera to see if it works as well as it does on the 80D. Sadly, I basically stopped using the T6S when I bought the 80D.

I'm shooting mostly raw now, and did not realize that HTP does affect raw files.  I'll enable it on my T6s and see what it does.  Thank you for your insights.

Hi WilbaW,  I have to respectfully disagree with you on this one. I read a similar response to yours recently and would like to see an official explanation by Canon as to how this works! HTP seems more intelligent than simply underexposing a stop and then applying a curve to bump the shadow and midtone details back up to correct exposure. I have found it recovers highlight details in situations where, if your theory was correct, the rest of the image would be VASTLY underexposed and would require significant shadow recovery. i.e. if I was to expose for the highlights the rest of the image would be ridiculously underexposed, by far more than one stop.

With HTP turned on (on a Canon 80D) I can basically correctly expose for the image, generally, and HTP takes care of the highlights. It does a far better job than anything one could do after the event in software. The fact that it "gets it right" across a broad range of lighting conditions tells me that it is varying the amount of recovery to what is needed. There is no way it is simply recovering one stop.

Turning the feature off suddenly makes my camera's DR seem very noticeably reduced.

Hi jvceac,

I'd suggest you try it again in a situation where it actually does something. Photograph a subject half in direct light and half in shade. Alternatively, just take some outdoor shots in a wide DR situation, such has midday sun on a clear summer day. It makes such a massive difference on my 80D that I leave it on by default unless I am shooting in very flat lighting or when using studio lighting. If I turn HTP off I lose a lot of highlight details.

I did some testing today and the results backed what I am saying. I deleted the images afterwards as they were just shots of a cat lying next to a window ledge. Had I known I was going to read this thread I would have kept the images. If you want me to I am happy to redo the test in a more useful shooting situation to show you how much difference it really can make.

Yes, the additional highlight detail even shows in Lightroom and Capture One Pro, not just DPP. The amount of difference you see with HTP on/off depends on the scene itself. It is night time here in Australia, but I will test my T6S at the first opportunity to see if it works as well as it does on my 80D. I hope you get the same results I am seeing.

Cooloox wrote:

Hi jvceac,

I'd suggest you try it again in a situation where it actually does something. Photograph a subject half in direct light and half in shade. Alternatively, just take some outdoor shots in a wide DR situation, such has midday sun on a clear summer day. It makes such a massive difference on my 80D that I leave it on by default unless I am shooting in very flat lighting or when using studio lighting. If I turn HTP off I lose a lot of highlight details.

I did some testing today and the results backed what I am saying. I deleted the images afterwards as they were just shots of a cat lying next to a window ledge. Had I known I was going to read this thread I would have kept the images. If you want me to I am happy to redo the test in a more useful shooting situation to show you how much difference it really can make.

That's interesting, I'll try it again. This past weekend I was shooting in a situation with a lot of highlight and shadow. Perhaps I was too quick to dismiss it.

Cooloox wrote:

Hi WilbaW, I have to respectfully disagree with you on this one. I read a similar response to yours recently and would like to see an official explanation by Canon as to how this works!

Don't base what you do on what people say, base it what works for you. Yes, you have said you are doing that, but it's not clear from your first post in this thread that you have done a valid comparison.

HTP seems more intelligent than simply underexposing a stop and then applying a curve to bump the shadow and midtone details back up to correct exposure. I have found it recovers highlight details in situations where, if your theory was correct, the rest of the image would be VASTLY underexposed and would require significant shadow recovery. i.e. if I was to expose for the highlights the rest of the image would be ridiculously underexposed, by far more than one stop.

I can't make sense of what you're saying there, but it probably doesn't matter, read on...

With HTP turned on (on a Canon 80D) I can basically correctly expose for the image, generally, and HTP takes care of the highlights. It does a far better job than anything one could do after the event in software.

That's such a huge claim that I have to assume it's made in ignorance of the facts.

The fact that it "gets it right" across a broad range of lighting conditions tells me that it is varying the amount of recovery to what is needed. There is no way it is simply recovering one stop.

Right, there's a curve, not a simple +1.

Turning the feature off suddenly makes my camera's DR seem very noticeably reduced.

Depends on what you are comparing and how you compare it. Let's set up a valid comparison.

Use a tripod, Av, f/8, manual focus, CWA metering, and RAW, on a normal naturally lit scene. Let's say you get 1/100 at f/8 and ISO 100 without HTP. Take that shot. With HTP you will get 1/200 and ISO 200. Take that shot.

If the effect of HTP is not apparent between those two shots, slow your shutter with +ve EC so that it is apparent. Keep the two shots you're happy with.

Now turn off HTP and set the same shutter as the HTP shot and ISO 100 in M. Take that shot. Post those raw files somewhere and we'll see if we can match the tones in the HTP shot from the manual shot.