Author Topic: raw  (Read 5558 times)

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Offline cj599

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raw
« on: October 10, 2009, 09:23:39 PM »
ive always been confuzzled on what shooting in raw does and how it benifits a photographer whats goo and whats and bad about raw?

Offline fother

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Re: raw
« Reply #1 on: October 10, 2009, 09:55:51 PM »
My take on this is pretty simple - the technical stuff can be pretty ... technical, but the concepts are fiarly straightforward

RAW is basically the photo as it is seen by the sensor. JPG is processed and compressed.

RAW files are therefore larger than JPG files (in terms of disk space). That's the main drawback of RAW.

On the plus side, RAW files give you far far far better control of white balance, colour correction, adjustment of contrast, saturation, recovering blown highlights, recovering shadows, etc etc. It's hard to express just how profound the difference in flexibility is.

Basically with JPG, the camera processes the photo as you take it, using a best guess of how you'd want it to look - and the changes are irretrievable - they can't be undone as the other data is discarded (hence the smaller files).

Because RAW is not pre-processed you often need to do a little more to get it looking 'just so'. In my experience this isn't intensive work, but can be done at batch level a lot of the time.

Of course, you can have the best of both worlds, and shoot RAW+JPG too... (personally I either shoot RAW or RAW+JPG - I always want the option of correcting problems / tweaking, so I always want the RAW, even if I'm 99% confident the JPG will be exactly as I want it to be)

Offline Radr

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Re: raw
« Reply #2 on: October 10, 2009, 10:20:30 PM »
By shooting in Raw, you are effectively capturing a digital negative, containig untouched raw pixel info direct from the image sensor.
this allows you to precisely cotorol how the final converted Jpeg,tiff or PSD is generated.
A raw file has ahigh degree of exposure latitude.
I hope it helps
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Re: raw
« Reply #3 on: October 10, 2009, 10:35:47 PM »
Raw is, if you like, 3 images.  1 for each colour.  The data is linear.  Not at all how your eye sees, or for that matter how your computer shows images.  It's, well, raw.  And that's why its spelt raw, not RAW.  It's unprocessed information - just as the sensor caught it.

The main advantage over JPG, is that it is not logarithmically compressed, so the range of data truly represents every photon captured (and noise too, but that's true of JPG's as well).

Since the camera has done no processing (well the Sony's do do some noise removal on raw) the data can played with in many ways most of them reversible (which is not often true of JPG).

The camera settings are tagged into the raw file.  So if you shoot a specific WB, contrast, NR, etc. settings, then that's what will show in ACR.  But ACR is _interpreting_ the settings, not showing the raw file as recorded - nothing can!  The settings only affect the way you _see_ the raw image, they don't change the raw image at all.

Raw lets you correct for light temperature and tint to the full range of source light characteristic.  This is much more limited in JPG.

As an example, let's say you shot one evening indoor with the WB set to tungsten.  The next day you take a shot of your kids in the park in the sunlight, but you forgot to change the WB to sunlight.  The image will be very blue.  You can correct the JPG, although far from "true".

OTOH, raw has no care about the source light characteristic, so you can easily set the WB on raw import.

Beyond that, in editing, you're working with the uncompressed data in its full bits/colour.  So with each edit function there is less loss than when working with a lower number of bits that have been compressed and re-compressed, sometimes many times.  (This has nothing to do, BTW, with the JPG image compression on save, that's another matter).

With PS CS3's raw converter I find that almost all of my basic image corrections for colour, contrast and so on are accomplished before the image gets into PS proper.  This is fantastic when all of the images are shot in the same conditions, then I get the settings right and apply the same settings to all of the images as a batch in raw converter.  That saves a hell of a lot of work.

Yes, raw files are larger.  Often 33 MB or so on the a900.  I save computer disk space by converting to DNG when moving the files from the data card to the computer (using Bridge, supplied with CS3/4).  There is also a free DNG converter from Adobe.  Most editing programs recognize DNG.  With DNG those raw files are reduced 40 - 50% in size (Lossless compression).

You can also, depending on your model use sRaw which is lossy-compressed, but I don't know of anyone yet who has seen a real difference in the files.  (Memory's cheap - I don't use sRaw).

Raw also gives you much better recovery of underexposed images (2 stops, even more) and overexposed (1/2 stop at least in most cases) so you can recover exposure boo-boo's much easier than with JPG where brightening an under-EXP results in muddy tones and lots of noise and calming down an over-EXP results in horrible blocking.  (You may get some posterization on brightening a 2 or 3 stop underexp in raw, but it's not nearly as ugly as recovering an under-exposed JPG).

You can also "expose to the right" in raw, where you move (usually with the aid of the histogram) the exposure to the right of the histo.  This lifts shadow detail.  Then in PS you "de-expose" the image to restore the tones to the right level.  Using the black point you can conserve shadow detail.  For example if the entire correctly exposed image was no brighter than middle grey, then you could expose it two stops brighter.  It will look over exposed in the camera monitor.  Back in the "lab" you re-expose it properly by moving the black point up.  This is much less versatile when done on JPG.
« Last Edit: October 10, 2009, 10:37:23 PM by Alan »

Alan

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Re: raw
« Reply #4 on: October 10, 2009, 10:39:09 PM »
By shooting in Raw, you are effectively capturing a digital negative, containig untouched raw pixel info direct from the image sensor.

Well, a digital "positive", actually. ;-)

And, nitpicking on, some Sony's do some noise processing on the raw data so they are not as pure as one would hope.

Offline chappo1

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Re: raw
« Reply #5 on: October 10, 2009, 11:35:25 PM »
I will not add to the technical discussion but tell you a story...I shot jpg when I bought my first DSLR.  I then moved to raw plus jpg but used to delete the raw files later as I did not really bother to learn how to process them.  Then, as Alan mentioned, one day I was shooting inside and had the white balance set to tungsten and forgot to change it for a landscape expedition next day.  it was either learn to use raw or junk the day's shots.
Now I shoot only raw and post process....john
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Offline winjeel

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Re: raw
« Reply #6 on: October 11, 2009, 12:27:10 AM »
...what the others have said. Plus, I shoot raw only. Because media formats change, it seems after processing, saving in dng may be the best long term option for compatibility and preserving as much of that data that is in raw, anyway. I haven't started saving anything in anything but sony raw and jpeg (after processing), yet.
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Offline Numpty

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Re: raw
« Reply #7 on: October 15, 2009, 11:35:32 PM »
How does raw and jpeg differ for blowing pictures up big as the filesize is larger for raw files is there more information so will it look better printed large?
Or will they both look the same its just you can adjust raw more easily?
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Offline dominicall

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Re: raw
« Reply #8 on: October 16, 2009, 06:42:53 AM »
How does raw and jpeg differ for blowing pictures up big as the filesize is larger for raw files is there more information so will it look better printed large?
Or will they both look the same its just you can adjust raw more easily?

When shooting RAW+JPEG in camera you don't get the option of shooting the highest quality JPEG (X-Fine) - it's actually RAW+FINE JPEG so there is an inevitable loss of detail.

Shooting RAW only gives the maximum detail as Alan explained, it's everything that hits the sensor. As well as processing enhancement, this also means that when processing a RAW file you get more detail than you would with shooting JPEG only.

Thus, if you want to blow up a picture poster size then RAW is the way to go.

That having been said, I had the photo I took of the sails on my folks boat and posted here printed 30"x20" and had it framed. It was taken with the Olympus mju tough camera which has a much smaller sensor that APS-C or FF which offer JPEG only.

If I stand very close to the picture on the wall I can see some artifacts, but framed pictures aren't meant to be viewed that way. Standing back it just looks like a lovely picture hanging on the wall.

Hope that helps.

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Offline Numpty

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Re: raw
« Reply #9 on: October 16, 2009, 06:01:45 PM »
Yes that explains it perfectly thanks
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Offline cj599

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Re: raw
« Reply #10 on: October 20, 2009, 04:42:53 AM »
thank you guys for all the help. so i will have to adjust the white ballence every time ?   also i been thinking about doing some large prints shooting in raw will help? i use picasa to edit everything i dont have the money to buy any other editing softwere.

Offline chappo1

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Re: raw
« Reply #11 on: October 20, 2009, 05:40:44 AM »
thank you guys for all the help. so i will have to adjust the white ballence every time ?   also i been thinking about doing some large prints shooting in raw will help? i use picasa to edit everything i dont have the money to buy any other editing softwere.

You would have gotten the Sony software when you purchased your camera.  This works fine it is just that many of us prefer the Photoshop option.

For simplicity look at it this way...when you shoot the best quality jpg you are presetting the Sony software in the camera before you go out and shoot.  If you shoot raw you can use the same Sony software on your computer to process the images after the shoot.

The computer software gives you a few more options and you can process each image slightly differently but that is a simple explanation that requires no expenditure.....john
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Offline dominicall

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Re: raw
« Reply #12 on: October 20, 2009, 07:41:43 AM »
thank you guys for all the help. so i will have to adjust the white ballence every time ?   also i been thinking about doing some large prints shooting in raw will help? i use picasa to edit everything i dont have the money to buy any other editing softwere.

When you are shooting RAW you can (theoretically) ignore the white balance setting since you can make any adjustments to white balance in the Sony software that came with the camera. Shooting in JPEG is a different matter as the white balance is set in the pixels and is much more difficult to adjust afterwards.

The Sony software is good but there are better alternatives.

A free RAW processing software that I've heard good things about is RAWTherapee - here.

If budget runs to it, you could get Photoshop Elements 8. Don't know where you are based but UK price on Amazon is £58.  With elements you can then use Adobe Camera Raw (included with Elements and updates can be downloaded) and then you'll have extra processing capability after you've processed the RAW file.

Hope that helps.

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Offline cj599

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Re: raw
« Reply #13 on: October 20, 2009, 07:05:12 PM »
im in the usa the elements is the one i was thinking

Offline cj599

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Re: raw
« Reply #14 on: October 27, 2009, 01:08:14 AM »
i cant install the raw converter on my laptop its a windows vista 64 bit i think i used the 64 bit installer tool at sonys web sight but only the pic motion viewer not the converter what should i use?