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01-06-2013, 08:42 PM   #31
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The histogram on the camera LCD is calculated from the converted JPG in the camera and gives only a hint of the underlying RAW data potential.

In under/over exposed images and especially with high dynamic range, the LCD histogram will be clipped at either end not only because the sensor was saturated (or received no light) but because of the compression from the original 12/14-bit space to the JPG 8-bit that drops all the fine steps. The resulting JPG will be clipped also with no way to recover anything from either end.

A RAW image can be processed to preserve any part of the 12/14 bit space and show details otherwise lost in the JPG compression. Obviously, if the same algorithm and conversion parameters are used to process the RAW data on the computer as in the camera, the resulting JPGs will be identical.

The power of the RAW data come to life when you want to change the default parameters or use a more advanced conversion program to get better results now or in the future. Think of having the option to do a single image HDR by changing the gamma curve in any part of the histogram and expanding the color steps without introducing gaps that will show as color contours.

01-06-2013, 08:57 PM   #32
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demp,
So I just took another underexposed shot on the Oly M43
The histo displayed in live view was at a lower level than the histo re displayed from the stored image, so i assume the camera boosts an underexposed image a bit.

How do we remap the level as you suggest? For example if the histogram stops at half brightness, that is 7 bits. How is that remapped to fill the 8 bits, for example.
Also, in doing that , is there any difference in the visible image displayed on 8 bit sRGB, compared to just dragging the brightness up a bit?

I am just using ufraw, it uses dcraw and I read that many of the commercial ones also are based on dcraw.
01-06-2013, 10:02 PM - 1 Like   #33
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QuoteOriginally posted by wombat2go Quote
demp,
So I just took another underexposed shot on the Oly M43
The histo displayed in live view was at a lower level than the histo re displayed from the stored image, so i assume the camera boosts an underexposed image a bit.

How do we remap the level as you suggest? For example if the histogram stops at half brightness, that is 7 bits. How is that remapped to fill the 8 bits, for example.
Also, in doing that , is there any difference in the visible image displayed on 8 bit sRGB, compared to just dragging the brightness up a bit?

I am just using ufraw, it uses dcraw and I read that many of the commercial ones also are based on dcraw.
The main difference is how smooth and natural the image looks after changing the brightness/exposure.

A 14-bit RAW image has 16,384 color steps per primary. An 8-bit one has only 256. When you map (compress) a 14-bit image to 8 bits essentially you are taking groups of 64 shades and collapsing them to one, assuming a linear map.

To correct an underexposed image (depending on the software you use) the exposure/brightness/shadows control reshapes the histogram by boosting and spreading the low values. If you use an 8-bit input image (JPG or otherwise) to generate another 8-bit output image, there will be some gaps after applying the correction which will show as color contours.

With the original RAW data, the input image is 14-bits. After applying the same mapping curve, you still have some gaps, but since you use groups of 64 shades, for each new one, some will have real data to give a continuous histogram in 8-bits.

The result will be a smoother, natural looking image. Depending on the noise level from the sensor, you can get your 256 shades that an 8-bit image can hold from a very narrow section of the histogram thus recovering details from an otherwise white or black looking image.
01-06-2013, 10:19 PM   #34
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Demp,
My Oly is 12 bit, 18% snr is
36 dB or 63:1 EV ratio at iso 100
30 dB or 31 :1 EV ratio at iso 400 where I normally use it
Do you mean that just by pulling the line in the raw converter GUI it automatically interpolates using the available bit depth from the raw file?
I tried that and could not distinguish on the Eizo any real difference pulling up a real underexposed shot compared to camera jpg.

01-07-2013, 05:13 AM   #35
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Wow, managed to inadvertantly start a fascinating thread. There is a lot for me to learn about digi photography that I did not bother to look into with my K-x. Now I have a K-30 I must make the time to look into this sort of stuff and treat my photography with the seriousness it deserves.
01-07-2013, 05:27 AM   #36
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QuoteOriginally posted by mikeSF Quote
While I can understand the ease of letting the camera generate a processed jpg by itself and not spending the extra time at the computer manipulating RAWs, I am way too much of a control freak to ever consider shooting in jpg. No way, not a chance. Far too limiting for my needs. And yes, I've done it, trust me, I have. To each their own, I suppose.
The al benefit I argue about shooting JPEG is it emphesises getting the shot right. I find too many people who think they can fix everything later in photoshop. That is just BS. Even if you shoot raw, getting JPEG settings correct benefits your workflow because thumbnails are displayed with the JPEG settings. If you allow your raw converter to import using your JPEG settings as well you start with where you want to be, or thought you wanted to be, etc...

The fact is, if you nail the shot for exposure and white balance, it does not matter.

The only valid reasons to shoot raw, in my opinion, are , better processing may come with newer software and time, and you can't process JPEG, or if you are shooting extreme shots, high key, low key, etc, where you are working so far off normal that the resolution is worth it
01-07-2013, 05:43 AM   #37
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Like mikeSF, I am way too much of a control freak; I want to tweak everything *before* I chop out more than half the data from a photo. No way would I let the camera do that.
01-07-2013, 05:46 AM   #38
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QuoteOriginally posted by Lowell Goudge Quote
The al benefit I argue about shooting JPEG is it emphesises getting the shot right. I find too many people who think they can fix everything later in photoshop. That is just BS. Even if you shoot raw, getting JPEG settings correct benefits your workflow because thumbnails are displayed with the JPEG settings. If you allow your raw converter to import using your JPEG settings as well you start with where you want to be, or thought you wanted to be, etc...

The fact is, if you nail the shot for exposure and white balance, it does not matter.

The only valid reasons to shoot raw, in my opinion, are , better processing may come with newer software and time, and you can't process JPEG, or if you are shooting extreme shots, high key, low key, etc, where you are working so far off normal that the resolution is worth it
Yes it does matter, I've left my camera in incadecent white balance and I had to pull it out and take few shots very quickly without thinking outdoors. Jpeg would mean I took bunch of ruined images.
I'm not going to adjust white balance every time I go from shadow, to cloudy or sunny on camera. I can do it later.

What is correct exposure? Maybe when I was shooting the photo I thought the pic would look great that way, but when I reviewed the photo later I felt that It should look a lot darker. It's subjective.
I think people who stick to JPEG they have not seen what raw can really do. Even nailing exposure with protected highilights etc, I will not be able to shoot lower than iso 200. Not to mention the photos will look flat.
I've a camera to take photos, not to fiddle with it and get in my way of taking photos, I can do that later on a pc.

Besides, what's the difference between using the raw developer included in camera and one on PC? Well, the camera one doesn't have the same flexibility and it's a lot harder to use.

01-07-2013, 05:46 AM   #39
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Blown highlight is blown highlight-the tiny bit of headroom some folks think they see is not significant.

The banding issue on a heavily manipulated JPG comes from trying to over-expand the dynamic range, using Auto-Levels or some such. This comes into play if you are way, way off-but can be helped using a layer/screen workflow, assuming you are not trying to salvage a real stinker-in which case not much will help in raw, either.

As noted, many raw converters use dcraw as the main engine-some use Apple's built in conversion, and some use Silkypix-but they all mostly use the same algorithm, and you can actually PICK the one to use in UFRaw-the differences are in the JPG converters and presets.

Yes, I have 6 different raw converters.

As to white balance, I can change it fine on a JPG, but I've taken some time to know how my cameras' settings affect the image.

Last edited by luker; 01-07-2013 at 05:48 AM. Reason: added last line
01-07-2013, 05:58 AM   #40
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Originally posted by luker
Not superior, may not even be different. Without corrections, you are just trading one set of presets for another.
QuoteOriginally posted by arcturus Quote
Ok thanks. Guess I'll stick with jpeg for now. Wish I had the time like so many others seem to have.
I have to agree with luker - HOWEVER, you can also adjust the presets in your camera and improve your jpegs - 'PRE' meaning before you take a picture.
Set your camera to something other than Auto (like Program), hit the info button and change how the camera's jpeg engine does its rendering.

In my opinion, Pentax's default of 'Bright' is just plain ugly most of the time. There are other presets that depending on the subject, might be better. Or you can tweak the jpeg rendering engine with your own preset.

Here is the rub. You have to make these choices before you shoot your picture, not after you shoot, and the only way you will know how your image will be affected is through past experience. On the other hand, if you shoot RAW, you can make these changes after you shoot the picture. More so, if you use a tool like Lightroom, you can build presets in the software similar to what Pentax has put in the camera and see exactly the impact on your image - or images because you can apply a preset to a whole batch if you so choose.

I'll be honest. If I always shot under tightly controlled conditions, I would take the time and make my own custom preset inside my camera and shoot jpeg. It is also true I wouldn't need much in the way of photo editing tools - mostly just a good resizer.

I am happy to say, that is not my photography experience. I shoot in a wide variety of conditions. Other than getting as close as I can regarding exposure and white balance, I'd rather not spend tons of time in the field ... for one thing, if I am with non or casual photographers, they don't have the patience to let me tweak things in the field, or the subject matter isn't going to sit still in the same light that long. So for me RAW is one of the most wonderful discoveries when I moved from digital point & shoot cameras to a dSLR. I have the joy I experienced shooting Ektachrome reversal film in my well loved Pentax Super Program, and I actually end up with a larger percentage of good images because I can do more of my thinking afterward.
01-07-2013, 06:20 AM   #41
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QuoteOriginally posted by luker Quote
Blown highlight is blown highlight-the tiny bit of headroom some folks think they see is not significant.
I mostly agree. Through my own dumb errors, that "tiny bit of headroom" sometimes has become very significant and salvaged something usable. And since I shoot RAW+, I can assure you that I couldn't always do such salvage jobs as well with the jpeg images as I could with the RAW.

When I use my dSLR like a glorified P&S for family snapshots, or other 'record-keeping' purposes, I will usually work with just the jpeg images - at most, see what auto-correct does and/or resize. But when I have an image worth looking at for more than 5-10 seconds in a family album or slideshow, I much prefer working with the RAW image.
01-07-2013, 06:20 AM   #42
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Why are so many here saying they can't correct white balance , EV etc of a camera jpg?
I can here in Gimp and even in basic Picassa. , and I thought that would surely be a basic feature of any decent photo editor.
01-07-2013, 06:27 AM   #43
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My workflow consists of almost always putting the images into Lightroom, editing out the bad ones and renaming the files. If I need to adjust an image I do so when I am thinking of either printing it or putting it out as a file to send off or use on my own computer. Nothing that I can see in my workflow would be easier if I shot jpegs unless I was able to shoot at a multiple of resolutions in jpg.Images processed in Lightroom 1 can be redone in Lightroom 4 for better results. I am not much into working hours on any one image however in RAW I do have more options if need be. I also started on film in the early 70s and still shoot film on a regular basis and do not understand people's comment on the difficulties of exposing slide film.

The only downside that I see in shooting RAW is that I have spent perhaps $60 more on cards than I would have if I shot jpegs and might need to buy harddrives ever 3 or 4 years instead of ever 10 years
01-07-2013, 06:30 AM   #44
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QuoteOriginally posted by wombat2go Quote
Why are so many here saying they can't correct white balance , EV etc of a camera jpg?
I can here in Gimp and even in basic Picassa. , and I thought that would surely be a basic feature of any decent photo editor.
Sure I can correct exposure and white balance on a jpeg. Particularly in regards to white balance, in my opinion, the RAW tools tend to be faster, easier to use.
01-07-2013, 07:05 AM   #45
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I have to check, but I remember trying to correct a jpeg that was shot in tungsten back to daylight settings, and it was damn near impossible. RAW I have no issues randomly changing white balance to suit me.
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