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-   -   What is the Percentage Range? (https://forums.steves-digicams.com/general-discussion-11/what-percentage-range-168336/)

Bynx Apr 2, 2010 11:46 AM

Quote:

Originally Posted by ac.smith (Post 1073851)
Granted your question is a hypothetical one but would we want to picture the sun, high in the sky as just a round orb?

A. C.

Actually I would. Id like to see a shot of the sun with solar flares and any texture it has, just like we see the moon.

Im getting lost in the discussion of interstellar light etc. In an outdoor scene on a bright sunny day if an exposure is made for an optimum image coverage as much of the range as possible, what would that range be? Its a given that Raw would be more than jpeg. So far as I understand it, that range would be 8 or 9 EV for jpeg and 12 for Raw. Now bracketing jpeg would increase that to a lot more than a Raw file. Now if we use our eyes in the same scene and allow them to adjust from the brightest to darkest areas, what range would our eyes have? And its equivalent to our best HDR, correct?

TCav Apr 2, 2010 12:30 PM

Actually, "interstellar" would be "dark", not "light".

The human eye has a dynamic range of about 90dB, but not all at the same time. The size of the pupil affects the dynamic range. Pupil sizes range from 3mm to 9mm. That would imply that 90% of the dynamic range of the eye is attributable to the action of the iris. It seems to me, therefore, that the eye with a fixed pupil diameter would have a dynamic range of at least 10 EV.

I have no doubt that this is a gross oversimplification, and welcome your comments and criticisms.

ac.smith Apr 2, 2010 1:57 PM

Quote:

Originally Posted by Bynx (Post 1073947)
Actually I would. Id like to see a shot of the sun with solar flares and any texture it has, just like we see the moon.

Im getting lost in the discussion of interstellar light etc. In an outdoor scene on a bright sunny day if an exposure is made for an optimum image coverage as much of the range as possible, what would that range be? Its a given that Raw would be more than jpeg. So far as I understand it, that range would be 8 or 9 EV for jpeg and 12 for Raw. Now bracketing jpeg would increase that to a lot more than a Raw file. Now if we use our eyes in the same scene and allow them to adjust from the brightest to darkest areas, what range would our eyes have? And its equivalent to our best HDR, correct?

Again you have two questions/comments. Pictures of solar flares, sunspots and other solar features starts off with HEAVY filtration to get the absolute values into a range that can be handled with our viewing or photograph equipment. If I were interested it would be straight to astronomy sources for me. HDR might be applicable but it would be well out of normal application of the process.

Now back to "normal" applications. I like TCav's estimate of the eye's dynamic range of EV10 and will use that for the rest of my comments.

A raw file will handle that (and this assumes the presentation media will handle it as well.) If the presentation is a print the most jpeg engines should handle the range actually available. This is the description of a scene in which the iris is not actually making any adjustments.

A scene in which the iris is adjusting will require both assumptions and simplifications. In this case I am assuming an outdoors, front lit scene between 2 hours after sunrise and 2 hours before sunset. Our hypothetical scene contains areas of interest that are both fully illuminated and those in open shade. Some "middle" gray for the fully illuminated portion would be EV15 and in the open shade area the same gray would be EV12. Applying TCav's estimate the eye is responding to EV7 (12-5) through EV20 (15+5) for a dynamic range EV13 including the iris's action. Even a raw photo doesn't quite handle this but 2 raw frames (DR 24EV) or even 2 jpeg frames (DR 18EV) HDR processed would. Including snow or light sand (middle gray 16) would raise the DR to 14 but would still be within 2 raw or 2 jpeg range.

This is simply a way to approach the question/problem. There are obviously scenes that could encompass a greater DR but I'll leave it to others to describe/analyze them. If someone has better numbers for any element of this analysis feel free to jump in.

A. C.

TCav Apr 6, 2010 6:45 AM

Yes. You're absolutely correct. That's the purpose of HDR: to represent the large dynamic range of a scene within the small dynamic range of the medium. You're compressing the dynamic range of the scene so that it will fit within a compressed 8 bit JPEG.

What HDR does for photographs is very similar to what dbx and Dolby did for audio. During recording, they compress the audio spectrum so the highs and lows aren't stored on top of, and become indistinguishable from, noise from sources in the equipment, and they amplify the soft sounds so they stand out from noise from sources in the recording medium. Then, at playback, the soft sounds that were amplified are reduced to their original levels, and the audio spectrum is expanded to its original dynamic range. In that way, the audio is truer to the original, and isn't corrupted by problems inherent in the recording process. This technique is referred to as companding. (Much of this technique has become unnecessary with the introduction of digital recording devices, though Dolby has kept pace with Dolby Digital technologies.)

musket Apr 6, 2010 4:36 PM

Here's an article that might explain more http://www.cambridgeincolour.com/tut...amic-range.htm

Bynx Apr 6, 2010 5:21 PM

Excellent article Musket, Thanks.

JimC Apr 9, 2010 6:34 AM

Quote:

Originally Posted by ac.smith (Post 1073851)
The best current jpeg engines across the board on 4:3, APS-C and full frame seem to deliver between 8.5 and 8.8 EV range although some still don't reach 8.

They tested JPEG images at 9.4 stops from the Sony A550 at ISO 200 (with it's DRO feature set to off). The full frame Sony A900 was also able to deliver 9.4 stops at ISO 200, and was still delivering a DR of 9.1 stops or higher through ISO 1600 with it's jpeg images.

ac.smith Apr 9, 2010 9:08 AM

Quote:

Originally Posted by JimC (Post 1076930)
They tested JPEG images at 9.4 stops from the Sony A550 at ISO 200 (with it's DRO feature set to off). The full frame Sony A900 was also able to deliver 9.4 stops at ISO 200, and was still delivering a DR of 9.1 stops or higher through ISO 1600 with it's jpeg images.

Yes, the A550 and A900 Sony seem to deliver impressive (class leading) DR in jpeg. The A900 also seems to have much better than most raw DR while the A550 seem to be a bit less than the norm. I say that cautiously on the A550 since they're labeling the raw chart a bit differently. The A380 DR, both jpeg and raw, seems to more like the rest of the marketplace.

A. C.


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