Technie question(s)...

I'm considering a 5D (I have 20Ds now...) for FF, but am reading good things about the highlight preservation logic in the Mark-something or the 40D (I don't know which).

Tech question 1: Does the 5D have this highlight preservation logic?

Tech question 2: How does this HPL (if that's what it's called) work?

I know the HPL (please humor my abbreviation) preserves highlight values, but it can't vary the ISO of the CMOS chip just in a bright spot (like a bride's dress). Unlike the Fuji chip, the entire Canon chip is one ISO or another; it's not possible to lower the ISO in just one place while leaving the other parts of the chip at another ISO.

So if my understanding of the CMOS chip is correct (and I believe it is), how does this HPL preserve highlight values on a bright spot while retaining shadow detail (i.e., from the samples I've seen, this isn't just an ISO override by the camera)...?

Do you mean HTP highlight tone priority? Improves the highlight detail, the dynamic range is increased by 18% gray to bright highlights, the graduation between the greys and highlights become smoother, it works very well

It is on the 1 MK3, 40D, I would guess the 1DS MK3, and again would guess it is on the to be released new 5D upgrade

The 5D does not, the 40D does (the 1DMKIII might as well, but I'm not sure about that). The function you're asking about is called Highlight Tone Priority. I can't speak for how it works, but it's not a function of the sensor but is rather a software feature. The 40D manual simply states the following:

Improves the highlight detail. The dynamic range is expanded from the standard 18% gray to bright highlights. The graduation between the grays and highlights become smoother.

Two caveats with this function is that ISO range is limited to 200-1600 and noise in the shadow areas may be slightly more than normal.

MaDProFF wrote in post #4253000
Do you mean HTP highlight tone priority? Improves the highlight detail, the dynamic range is increased by 18% gray to bright highlights, the graduation between the greys and highlights become smoother, it works very well

It is on the 1 MK3, 40D, I would guess the 1DS MK3, and again would guess it is on the to be released new 5D upgrade

Although Im not sure of how it does it, I just wanted to clarify that it doesnt increase dyanmic range by 18%. It adds DR between 18% Gray ( like a a gray card. Also just a "middle" gray ) and maximum highlights.

Mark_Cohran wrote in post #4253035
The 5D does not, the 40D does (the 1DMKIII might as well, but I'm not sure about that. The function you're asking about is called Highlight Tone Priority. I can't speak for how it works, but it's not a function of the sensor but is rather a software feature. The 40D manual simply states the following:

Improves the highlight detail. The dynamic range is expanded from the standard 18% gray to bright highlights. The graduation between the grays and highlights become smoother.

Two caveats with this function is that ISO range is limited to 100-1600 and noise in the shadow areas may be slightly more than normal.

The 1D MkIII does indeed have it and it limits your ISO to 2oo-16oo. 100 isnt selectable.

Same with the 40D

AdamLewis wrote in post #4253074
The 1D MkIII does indeed have it and it limits your ISO to 2oo-16oo. 100 isnt selectable.

I meant to type 200-1600. I've edited my original post to reflect the correct ISO range.

Yup, that's it...HTP.

Ya know what my guess is of "how" it works, since the CMOS chip can't add dynamic range in a portion of the chip?

My guess: it's software only (as already stated by another poster) and processes the RAW data (16,000+ data values rather than 256 of JPEG) with a bias in the bright areas. With the RAW data in a matrix, it could use the bright values in any area of the image it wants to when creating the final JPEG. Assume that without HTP, the JPEG converter makes a linear decision as to what values compress to their JPEG equivalents. With HTP, the JPEG converter looks at highligh values differently and compresses them with more separation in the bright (or near-saturated) areas. Rather than make a linear decision, it looks to emphasize smaller differences near the saturation point.

If I'm correct, this feature (HTP) could be added to the firmware of ANY camera, new or old. Same for ETTL II - it could be put on an old digital Rebel and fix the flash exposure problems. I bet Canon won't do it to preserve new camera body prices, and make you buy newer systems.

MaDProFF wrote in post #4253000
Do you mean HTP highlight tone priority? Improves the highlight detail, the dynamic range is increased by 18% gray to bright highlights, the graduation between the greys and highlights become smoother, it works very well

It is on the 1 MK3, 40D, I would guess the 1DS MK3, and again would guess it is on the to be released new 5D upgrade

Mark_Cohran wrote in post #4253116
I meant to type 200-1600. I've edited my original post to reflect the correct ISO range.

A little off topic, but you change your avatar like every week!
I know people by their avatars and if not for you being in all of them, Id think you were always a new user haha

AdamLewis wrote in post #4253454
A little off topic, but you change your avatar like every week!
I know people by their avatars and if not for you being in all of them, Id think you were always a new user haha

Just trying to keep you on your toes.

I gotta tell ya, this HTP feature would benefit me enough that I now am willing to wait for Canon's next FF camera model. I'm convinced they won't put HTP in a firmware update for existing cameras, it won't sell the newer models.

I spend a huge amount of time managing highlight saturation when shooting events, so even a minor assist by the camera would help me tremendously.

Darn...was close to a 5D!

RVsForFun wrote in post #4256232
I gotta tell ya, this HTP feature would benefit me enough that I now am willing to wait for Canon's next FF camera model.

HTP is available in FF today, in the new EOS-1Ds Mark III.

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A question about HTP: Is it clear that it's only for jpeg? That RAW is not benefitted by it? This would be good to clarify so that those using RAW don't rush blindly for something that won't help!

Yes, it's good for RAW.

Imagine this...you capture an image and that image contains blown-out highlights. Neither JPG or RAW can resurrect those highlights...they are lost forever.

Now, there may be some software to fabricate some highlight content, but that's out of scope of this reply.


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AperturePriority wrote in post #4258225
Yes, it's good for RAW.

Imagine this...you capture an image and that image contains blown-out highlights. Neither JPG or RAW can resurrect those highlights...they are lost forever.

Now, there may be some software to fabricate some highlight content, but that's out of scope of this reply.

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OK, if it's good for RAW, that would imply tweaking something in the capture process, rather in the software -- I would imagine since it only works above ISO 100 it would involve a "smart" reduction of the amplification applied to the sites (to "up" the ISO from the base (100)) that were judged overexposed...?

I don't know how else it could work with RAW.