Mr. Westfall: question about Highlight Prio.

[ron_purdy]

Hi Chuck, do you know if the newest sensors (IdsIII, 1DIII, 40d) really have increased dynamic range over previous sensors, or whether the newer cameras simply use Highlight Priority modes to
tweak the data which has essentially the same dynamic range as before?

Best,
-ron

[ChuckWestfall]

Hi, Ron:

We haven't made any claims about increasing dynamic range with our current image sensors. Instead, we've said that dynamic range remains about the same or similar to previous generations despite higher resolution and smaller photosites. (Check 1Ds Mark III vs. 1Ds Mark II for example.)

Highlight Tone Priority mode has no effect on the actual dynamic range of the image sensor. It's just an alternative method of image processing that preserves more highlight detail than our standard processing, without significantly altering midtones or shadows. The effect of HTP is enhanced by our 14-bit A/D converter, which provides finer tonal gradations than the previous 12-bit system.

[ron_purdy]

This quick response is very much appreciated. Thanks Chuck!

[RalphEisenberg]

It is also much appreciated for its clarity! Many thanks.

[ron_purdy]

Thanks Chuck, I have a follow-up question.
So, when someone reviews the 40d and concludes the following, what they are actually seeing is not, in fact, an increase in dynamic range?
> >

• Good tonal response, dynamic range extended compared to competition, EOS 30D >>
• Highlight tone priority option delivers even more dynamic range with very little downside >>
• One surprise came from our testing of the cameras dynamic range, it delivered a consistently higher range than both the competition and its predecessor. The majority of this improvement, however, was in the shadow range, a function we presume of the new 14-bit processing pipeline.>>

>
I am just wondering if the actual dynamic range has increased *at all*, or if it’s purely software and processing advancements which the reviewers are seeing – and describing as “increased dynamic range.”
I realize that a lot of the HTP processing is taking place during exposure, but I am left wondering if some of this new processing be done to files from older cameras using DPP in the future?


Again, thanks!

-ron

[ChuckWestfall]

Hi, Ron:

To put it in your words, the dynamic range of the 40D image sensor itself has not increased at all compared to the 30D. In our words, dynamic range of the 40D remains the same as the 30D despite higher resolution and smaller pixels.

What you're seeing with HTP is a modified image processing algorithm combined with the effects of 14-bit A/D conversion of the RAW image data. Reviewers who discuss the benefits of HTP are effectively pointing out how image processing modifications combined with a higher bit-depth in the RAW image data can improve the rendition of highlight details compared to earlier cameras without those features.

And once again, the 14-bit A/D conversion enhances the effect of HTP because it provides 4 times as many gradations to choose from as the RAW image data from cameras with 12-bit A/D conversion.

[ron_purdy]

Chuck, is the below assessment my Thomas Knoll accurate?

quote

Thomas Knoll - 5:44am Oct 14, 07 PST (#1 of 15)

In camera, all this is happening in raw mode with HTP is the exposure is reduced by 1-fstop.

This creates a raw file with 1 extra stop of headroom. Exactly how the raw converter handles this is up to the raw converter. Camera Raw *by default* boosts the exposure slider zero point back up by one stop.

For many images, it is absolutely the correct thing to do. If you are taking photographs of normal scene, and have the camera set in HTP mode, then this is EXACTLY what you want. Rolling off the highlights like DPP does would just create a muddy image.

If you have an image that you needs rolled off highlights rather than boosted highlights, that is trival to do Camera Raw. Just boost the recovery slider (for versions of Camera Raw with that control). Or you can do a combination of reducing the exposure slider and increasing the brightness slider, which has the same effect.

end quote