Which of these 5D2 functions affect raw images?

Hi, will the following 5D2 functions affect raw images, or only jpg images?

- Peripheral illumination correction
- Auto lighting optimizer
- Highlight tone priority

Thanks in advance!

Highlight Tone Priority because it effects exposure.

Hmm, well, let's back up a little bit...

The use of one of those settings can certainly influence how either your camera or you decide to expose, that's true.

Now then the question is, are any of those settings actually applying their "influene" on the actual Raw data? So, if you have peripheral illumination correction on, does the camera apply this to the Raw data, so that it now becomes the Raw data (visible to all Raw processors)? Or, does ALO apply a "curve" to the Raw data so that the Raw data is now "corrected" for highlights and shadows? Or, with HTP, where the analog data is supplied by an ISO that is one stop lower than the ISO you specified in-camera, and then a curve is "applied" to boost shadows while keeping the highlights "down", is this processing applied to the Raw data?

Now, this is an interesting question! I'll say that I don't have a camera with PIC or ALO, but I do have one with HTP. What has made things interesting is that if I shoot using HTP and bring the shot into Lightroom, you do see an effect applied to the shot -- it's "different" from a shot taken at the one stop lower ISO -- you do see better shadows with the HTP shot. And certainly if you shoot at the higher ISO that you set the camera to, but shot without HTP, Lightroom shows the highlights brighter.

Like I said, I don't have PIC or ALO so have never seen how Lightroom treats those images -- it would be interesting to see.

Now, since that is what my testing shows, I've asked the same question about HTP: does this prove that the curve is actually applied by the camera to the Raw data, and so the Raw data is now changed?

Well, some of the people I've had this conversation with actually have used software tools to check this out. What they have reported is that, in fact, when they examine a Raw shot done with HTP that in fact it is identical to one done at the lower ISO without HTP. So, their findings are that HTP does not alter the Raw data.

As to why it shows up in Lightroom, their assumption has been that Canon puts an HTP "flag" in the Raw file metadata and that Lightroom has been developed to "read" that flag and apply its own curve. And they point out that, in fact, Lightroom does a job at this that is not as good as an out-of-camera jpeg or, presumably, a Raw file processed in DPP.

Well, all I can do at that point is to say "OK..."!

But, something importand to consider is that if you are shooting Raw and you properly expose to preserve highlights, then you can do your own processing and have better control than if you just depended on HTP, and yes, that was part of my testing. I was able to match and even improve on an HTP jpeg by processing the shot with the lower ISO that preserved the highlights which, at the higher ISO would have been clipped at some point.

Now if I was shooting jpeg, I'd use HTP. ALO, high ISO noise reduction, PIC, all that, because the camera does in fact process the Raw data with those things. And, when it produces a jpeg, it compresses the image data to 8 bits and discards unneeded data. So, as we know, jpegs have less "latitude" to adjust these tones and that can make a big difference. So, in my HTP example, with the Raw file I could smoothly adjust the shadows and midtones to balance with the retained highlights, but from my experience with jpegs, I know that I would be asking for trouble if I routinely took on that task rather than using HTP. You can succeed to a degree (not too much noise in the shadows), you can get reasonably good results over and over again, but then here and there, however often, you will run into that problem jpeg and be banging your head against the wall.

So then, what about ALO and PIC? Well, first, I don't know how Lightroom handles these, it would certainly be interesting to know. But, what I said about the Raw processing still applies -- you could meet or beat the results if you have the skills with your Raw processing.

And then, you have DPP, the Canon Raw software. I presume that DPP recognizes and applies these three settings, assuming that they are metadata flags and not something "burnt into" the Raw data. In fact, if you open an image in the DPP editor and go to the NR/Lens/AlO tab, you should note that there is actually an ALO on/off checkbox (along with adjustments) which tells me that ALO is not applied to the Raw data and so is in fact a metadata flag. There is also an on/off option for the various settings the camera has for lens corrections, including the PIC function. If your camera does not have those functions, then ALO and all of them are grayed, not available.

So, because of what we see in DPP the conclusion would be that ALO and PIC (and other lens corrections settings are not "burnt in" to the Raw data. I don't see anything about HTP in DPP, which may continue to be confusing, but like I said when shooting Raw I don't use it (and I never shoot jpeg).

Well, did I help or just add to the confusion?

RAW converter aside, here is an explanation, it is what I've been led to believe over the years;
http://www.cambridgein​colour.com …/thread2052.htm​#post17586

I suspect HTP does but not the rest.

windpig wrote in post #13055493
RAW converter aside, here is an explanation, it is what I've been led to believe over the years;
http://www.cambridgein​colour.com …/thread2052.htm​#post17586

Heh! Since it's a forum thread it reminds me of the discussions we've had here since this camera "feature" (HTP) came out -- and, most of the "knowledgable" people who posted came to the same conclusions that I posted above, but of course since Canon And Adobe have not as far as I know disclosed the "inner workings" of all this all such things are "educated guesses" and so you'll see some variations even amongst "experts".

My own tests on HTP were done back in early '08 with my 1DM3:

http://www.pbase.com/t​onylong/mk3_htp_test

But, like I said earlier, these were done using LR3 and so were not analysing the actual Raw data but only the Lightroom "interpretation". So, if what I posted above and others posted in that Luminous Landscape thread are correct (I believe I saw that thread way back then or one very much like it) then the answer to the OP is no, the Raw data itself is not affected. And, if you shoot Raw you can get the same results shooting the Raw at the lower ISO and applying your own "curve".

This actually applies to all the setting that do image manipulations to your images in processing jpegs -- not just the three mentioned here, but the "old standards" Picture Styles and WB/Color Tone as well as things like High ISO Noise Reduction. Raw shooting does mean it's up to you do do the work, but you reap the reward of having control of these process, and, potentially, of enhancing a photo to better-than-jpeg quality!

Hi Tony

I haven't read all the posts and testing that's been done relative to HTP, so forgive me if I'm off, but here's my understanding of it. It's appears to be another form of auto ISO in that the camera will underexpose by 1 stop and then the camera (or DPP) apply what every enhancements are needed to bring back the exposure. With that said, it would be the only one of the three things the OP mentioned that changes the RAW data to the point that it can't be unchanged (underexposed).

Maybe I've spent to much time in the nice Northwest fall sunshine

Well, yes that the camera exposes at the lower ISO, so in that sense it underexposes shadows and midtones. That is the light the sensor collects and the ISO amplifier applies "standard ISO amplification to and so the result is the Raw data, the same as you would get with the lower ISO setting. What does not affect the Raw data is the "rest" of HTP, what makes HTP "different" from either "native" ISO setting -- it does not apply the tonal curve that boosts the shadows and midtones while retaining the highlights.

So, when you suggest that HTP alters Raw data, well, you have to qualify that -- you can make it a "yes and no" type of answer, as long as people who are actually paying attention to the Raw understand what they are seeing.

Like I said, Lightroom throws a curve ball at us by "trying" to handle HTP, but another Raw processor may just present the Raw file with the lower ISO. The highlights will look good, whereas the shadows and midtones will be underexposed -- in other words an outcome that many Raw shooters consciously set up in their exposure! In other words HTP gives us a Raw file that is "the way to do it when shooting Raw"!

I know this is an old thread but I got a question that I cannot find but I'm sure it is out there somewhere. Does HTP and ALO work if shooring in manual in jpeg format?

And do they work when using a speedlight? But I have a 50D.

Thanks.

If you turn HTP and/or ALO on, then sure they affect the jpegs -- that's what they are for. It doesn't matter what exposure mode you use (Manual, Av, Tv, P) -- those settings work on the image after it is taken, prior to saving the jpeg.

Since the original question was how the affect a Raw image, then that's a different question! Some Raw processors read the "tag" for HTP/ALO and apply some processing "under the hood", others ignore the tags. But that's for Raw files/shots, not jpegs.

Ok thank you..but when using a speedlight, does it affect the image or over ride what those two functions do because it is lighting them up? Or do they process the image even after it is taken with flash and then adjust?

Hmm, well I can't answer that -- I never turn HTP on and I don't have a camera with ALO...if you have a camera with both functions, try it out and let us know!

I don't see that having a flash would "turn off" those functions, but it may affect how they work...I just don't know 'cause I don't use 'em!