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Old Apr 21, 2005, 11:08 PM   #11
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Thanks for all the info, I think I cant be bothered to shoot RAW most of the time, I find it's enough work editing a jpeg and I presume with RAW it means even more editing:roll:
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Old Apr 22, 2005, 4:29 AM   #12
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aladyforty wrote:
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with RAW it means even more editing
Exactly. And don't forget that most of us can do automatic exposure bracketing of our high quality jpegs to make sure we get at least one correctly exposed shot, and often one that's correct for the highlights and one for the shadows. I always bracket the exposures when there's a shot I really don't want to foul up.

You still see professionals with Hasselblads on tripods, still bracketing here and there. This costs money with film, but costs us nothing but a bit of space on the memory card.
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Old Apr 22, 2005, 6:05 AM   #13
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aladyforty wrote:
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Thanks for all the info, I think I cant be bothered to shoot RAW most of the time, I find it's enough work editing a jpeg and I presume with RAW it means even more editing:roll:
I feel kind of foolish to speak out about this since I'm just a amateur stumbling my way along, and I actually only began shooting RAW yesterday! :O but the way I feel right now can be expressed as "I once was blind, but now I see."

Until now I've always shot JPEGs and adjusted values in PSP; pretty simple stuff. Before starting RAW I read quite a few online articles and waded through the theory as best I could, and I actually tried (feebly) to process a few images using the Olympus Master software that came bundled with my E-300 (only two weeks old), but the Oly Master user interface is a mess, and it runs like molasses in January.

Yesterday I downloaded the free version of RawShooter Essentials (RSE) and tried it out. Like Night and Day. I'm still in the evaluation stage, but at this point I am very impressed. Yes, I processed JPEGs before, but I, at least, could never get results like I got with RAW--and pretty easily, to boot.

As someone else suggested, digital cameras have narrow dynamic range, at their best much like slide film, with the same propensity to blow out highlights. One thing RAW lets you do is to substantially underexpose a scene in order to tame the hot spots, then develop shadow detail that wouldn't be salvageable in a JPEG (similar work can indeed be done with curves on JPEG images, but IMHO not to the same extent, or without messing up the color as severely).

Yesterday, I went out for a test run and shot a number of images at a local shrine; the sun was out with puffy clouds here and there, and it was striking parts of the shrine's roof, but the shrine itself is surrounded by a copse of trees that puts most of it in shade; the area under the eaves was almost pitch black from where I stood. I was shooting simultaneous RAW and SHQ (Oly's highest quality JPEG); here's the original JPEG for one frame (resized only):


I underexposed the frame by several stops to prevent the highlights along the roof and in the sky from blowing out; although the sky shows blue, part of it is right on the borderline of being blocked out white.

As I said earlier, some of the shadow detail under the eaves could be brought up conventionally by using curves and such, but when I tried doing that on the original jpeg, the results were less than good; the borderline area of the sky became solarized, and the colors became very hard to manage (I admit, someone else might have had better luck at it).

At any rate, when I opened the RAW image with RSE and corrected it (very logical procession of operations), it was possible to save the shadows without solarizing the sky or weirding out the green.



I probably wouldn't have gotten into RAW, either, if it hadn't been for the ease of using RSE (not to mention its being free); there are other conversion programs out there, but I'm going to stick with RSE until I get a better grasp of the process. RSE runs like the wind on my computer; the sliders respond instantly, while Olympus Master required about 5 seconds to complete each incremental operation.
You can also set up images in a queue, and process in the background as you correct a different photo. I'd give it a try at least.

(I have no connection to any of these products other than being a user. Like everything else, your mileage may vary).

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Old Apr 22, 2005, 10:12 AM   #14
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Hi Norm

Welcome to the shooting in RAW club...:-)

I read in a remark above that you cannot get back blown highlights even in RAW. Or in your case, shadow.

Absolutely not true! While not absolutely the same as true exposure control, you do have, for all PRACTICAL purposes, a play of two F stops in either direction.

What can be said is that RAW is not the same as prayer. If the highlights or shadow are more than two stops blown, even RAW wont help...

This is reality, and for those sceptics, they really ought to put this to the test, as you have demonstrated.

dave

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Old Apr 22, 2005, 5:47 PM   #15
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DBB wrote:
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I read in a remark above that you cannot get back blown highlights even in RAW.
That was me. What I said was that you obviously can't in reality alter the exposure you gave at the time, but you can obviously twiddle the brightness and contrast of the pixels. Getting detail back in achunk of image where the CCD registered its maximum intensity seems naively to me to require "Dr.Who" style time travel.

If, as everyone seems to be saying,it is in fact possible to simulate exposure compensation, please could someone explain to me how it works, and how it's any different from twiddling brightness & contrast or applying a curve in an image editor? Might it be that you're working with more bits per pixel, so less is thrown away?

Clarification from an expert who knows how the data gets from the CCD to the RAW file and then to thetif or jpgwould be welcome.
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Old Apr 22, 2005, 7:13 PM   #16
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Alan T wrote:
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DBB wrote:
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I read in a remark above that you cannot get back blown highlights even in RAW.
If, as everyone seems to be saying, it is in fact possible to simulate exposure compensation, please could someone explain to me how it works, and how it's any different from twiddling brightness & contrast or applying a curve in an image editor? Might it be that you're working with more bits per pixel, so less is thrown away?

Clarification from an expert who knows how the data gets from the CCD to the RAW file and then to the tif or jpg would be welcome.
No expert me, but I believe you're on the right track with the bits per pixel; since JPEG is 8-bit and the sensor is 12 or 14 bit, information is getting spread over fewer bits in JPEG, and as signals get clipped, it foreshortens the top and bottom zones (my guess).
8 bits =256 levels, while 12 bits (most sensors) = nearly 5000 levels. When converted to TIFF for export, the 5000 levels are spread over the full 16 bit workspace for 48,000 levels. See Michael Tapes article about this at:

http://www.luminous-landscape.com/tu...aw-files.shtml

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Old Apr 22, 2005, 8:06 PM   #17
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Unfortunately I'm no expert either. But I know enough from practicval experience that Norm is wrong on this. I know this because I've experimented with shooting in TIF...:-)

Now there is an explanation I read somewhere, and forgive me for bolluxing it up, but briefly the RAW file doesn't KNOW that the sensitivity was already predetermined.

When you use RAW, It's NOT quite as good as actually having the right exposure level. You are doing what someone in a darkroom would do, by pushing the film or it's opposite. So all RAW importers allow 4 stops of play in either direction.

I've found (as the article I read mentioned) that the practical level or results is 2 stops. past that, you get to much noise. You get noise ANYWAY, but the noise is not really objectionalble.

To dispute the technical aspects of the above will not present you with great difficulties

:lol:

I'm no techy. But to refute the PRACTICAL aspects of what I'm saying is going to be rough. In my personal tests, I can restore the blown highlights in an image because the digital data is still there. I cannot do this with a TIF or JPEG. And of course, as I said, if the images is too overexposed, not even RAW is going to help :sad:

I don't know of a professional shooting digital, who doesn't use RAW for their serious work, and the reason is as I described, as well of course of such issues as WB, etc.

Keep in mind that while you can use the eye dropper in the levels command to adjust white - you have to have WHITE there to begin with to use that option. Moreover, even then there is no fine tuning.

With the PS importer or other programs, the temperature can be adjusted exactly, with a fine tuning that doing it later is simply not available.

dave
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Old Apr 22, 2005, 9:29 PM   #18
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DBB wrote:
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Now there is an explanation I read somewhere, and forgive me for bolluxing it up, but briefly the RAW file doesn't KNOW that the sensitivity was already predetermined.

To dispute the technical aspects of the above will not present you with great difficulties

:lol:

Indeed. The ISO equivalence amplification happens before the analog to digital conversion. RAW is digital, therefore the "sensitivity" has been applied.
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Old Apr 23, 2005, 1:05 AM   #19
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Itall boils down to bits and bytes :blah:

The jpg is an 8-bit/channel file, the 3 * 8-bit channels compose the 24-bit image a jpg is capable of. It is produced by the camera taking a chunk out of the raw image the sensor produces and throwing away the rest of the information.

The RAW file from the Canon 20D is a 12-bit/channel file, the 3 * 12-bit channels produce a 36-bit image. It contains a much largerrange of colors that a jpg is capable of. This is why you can slightly "adjust exposure" when working from aRAW file. Or produce an image with a much larger dynamic range if your entire work-flow is 16-bit (Confusers round up to nearest byte boundary), Which Adobe-CS is capable of doing.

The MysteryMatics of it.
  • 24-bit image captures 256 shades per 8-bit channel producing 16.7 million possible colors (2^24) [/*]
  • 36-bit image captures 4096 shades per 12-bit channel producing 68 billion possible colors (2^36)[/*]
The MF backs for the Haselblad and others are full 16-bit, producing 48-bit images.

That is 32,768 shades per channel and :homey:Whats 2^48? :-)possible colors.

Duh..stupid brain it's:281 trillion possible colors :?

:cart:Myself I'd prefer it if everyone used jpg except me. :cart:

Peter.


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Old Apr 23, 2005, 2:00 AM   #20
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PeterP wrote:
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Itall boils down to bits and bytes.... the 3 * 12-bit channels produce a 36-bit image.....This is why you can slightly "adjust exposure" when working from aRAW file. Or produce an image with a much larger dynamic range if your entire work-flow is 16-bit
Excellent, thanks. That's what I wanted to know, and explains everything. We got there in the end!
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