Raw vs bitmap

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Tom

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Could someone please explain the difference between Raw and Bitmap formats. It would seem to me that they're the same, but the numerous mentions of "raw format" make me think this might not be correct.

TIA.
 

Bob Buchanan

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Tom said:
Could someone please explain the difference between Raw and Bitmap formats. It would seem to me that they're the same, but the numerous mentions of "raw format" make me think this might not be correct.

Tom, thank you for creating the new Photography and Imaging section. A number of our members are to varying degrees familiar with film photography. However, most all of us have the need to learn more about digital photography. By having a separate section for this, hopefully more discussions will happen -- and all of us will learn and benefit.

Am not a technical expert inside the digital camera -- and really don't care to be. In film photography, I considered myself a "shooter" and only wanted to know enough darkroom to be a better "shooter".? But that changes now for the digital shooter. And your question is an example.

The bitmap is a Windows format that stores all the color info about each pixel of an image in a single byte. It is not a machine dependent format -- in that you can send it to most any printer or whatever. So it's a great format for printing images for both these reasons.

The drawback of a BMP as output of the image processor in a digital camera is that it is too large. So most digitals present the image in a compressed state -- the JPEG. A JPEG is sort of a compressed BMP.

The drawback of the JPEG is that each time you modify and save it, or "just" re save it, it compresses once again -- and each time this happens, the quality (or information stored about each pixel) is lowered.

The raw data that is spewed out by the image processor in a digital camera can be stored as is in the RAW format. It is not in a format that can be printed -- and must be further processed by computer software to convert it to a BMP, JPEG, or whatever.

The reason I mention that the attitude about understanding darkroom has changed is because of the ability to output in RAW vs. JPEG. The RAW format allows me to essentially shoot the picture over again in the SW darkroom. An example is color balance of an image -- white balance, white point are terms used in digital.

When I shoot, I set the white balance to the light conditions I have at the time. If under incandescent lights I set differently than in bright sunlight. However, if I screw up the setting plus have told my camera to save my pictures in JPEG format -- I will have a tough time changing the white balance with the software. It can be done, but easier and more effective working with the RAW format.

If I saved in RAW, I just change that setting with the SW to what it should have been when taking the shot. Same with other camera settings that are stored in the RAW but not in a JPEG as an image wide setting.

So think of the RAW as a negative that you would take into the darkroom. NEVER modify and re save it. Always create a BMP or whatever from the changes you make just as you would create various prints from a negative. In the film darkroom, we mess around with a negative to correct stuff we did while shooting as best we can. We can now do the same thing with the RAW in the digital darkroom -- but more effectively because we are changing a setting vs. changing the results of a setting.

The drawback of shooting in RAW is that if doing sports or moving wildlife, the image processor cannot get images out to storage as fast as just shooting in JPEG to begin with. So if I want to catch a bird in flight, my XT is capable of shooting 3 frames per second -- but not in RAW, so I would miss some good shots.

And that gets back to Karl's point of knowing all there is to know about what it takes in camera settings "before" you shoot vs. waiting to fix everything in the SW darkroom. That's because one will not always want to shoot in raw -- and will want that JPEG to be as perfect as possible to begin with.

Most better digitals now allow the shooter to get "both" RAW and JPEG on each shot. That's great because it essentially give the shooter a negative (RAW) and a proof print (JPEG) to look at.? However, hopefully one can see the pros and cons of that from my response. Most of my subjects are sitting still, so I like to have both. Jerry Fitzgerald shooting at the race track might prefer JPEG only.

Hopefully others will add to or correct my thoughts. I have never taken a RAW into digital SW other than to get a BMP or JPEG copy so what I say here is mostly from what I read about this format. My older digital did not give me such a format, whereas the Canon XT Rebel will do all kinds of amazing stuff.
 

Ned

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Here's what Wikipedia (http://en.wikipedia.org/wiki/Image_file_formats) has to say about RAW and BMP formats:

RAW

The RAW image format is a file option available on some digital cameras. It usually uses a lossless compression and produces file sizes much smaller than the TIFF format. Unfortunately, the RAW format is not standard among all camera manufacturers and some graphic programs and image editors may not accept the RAW format. The better graphic editors can read some manufacturer's RAW formats, and some (mostly higher-end) digital cameras also support saving images in the TIFF format directly. Adobe's Digital Negative Specification is a recent (September 2004) attempt at standardizing the various "raw" file formats used by digital cameras.

BMP

The BMP (bit mapped) format is used internally in the Microsoft Windows operating system to handle graphics images. These files are typically not compressed resulting in large files. The main advantage of BMP files is their wide acceptance and use in Windows programs. Their large size makes them unsuitable for file transfer. Desktop backgrounds and images from scanners are usually stored in BMP files.
 

Tom

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Bob Buchanan said:
..thank you for creating the new Photography and Imaging section.

Glad to do it Bob. Over the years, I've watched the interest/participation increase when the subject is discussed and, as you suggest, others like myself learn something from the discussion.

Thanks for the detailed and considered response to my question re file formats.

The bitmap is a Windows format that stores all the color info about each pixel of an image in a single byte. It is not a machine dependent format...

I understood the differences between bitmap and compressed file formats, but was confused by the term "raw", especially when used in the context of "I shoot raw". From what you and Ned have said and from what I read elsewhere, it appears that the "raw format" is a proprietary format of the camera manufacturer. I'm reminded of one or more of my prior DSCs that saved in a proprietary format; At the time I either didn't understand the significance or couldn't be bothered to find out.

Let me elaborate on my question a little ....

I'm currently evaluating a couple of cameras before the respective store return policies run out (Since they have different functions I may end up keeping both, but more on that in a different discussion). One of these cameras has options to save images in "uncompressed tiff" or two sizes of jpeg. The same scene produces file sizes of 17.0Mb, 2.90Mb and 1.45Mb respectively. I'm trying to figure out if I'd be missing out on something (in the digital darkroom) by not choosing a camera that saves in "raw" format vs the "uncompressed tiff" format. e.g. your comment ...

The RAW format allows me to essentially shoot the picture over again in the SW darkroom.

Is this ability lost if the camera saves the images in "uncompressed tiff" format?
 

Tom

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Ned,

Thanks for the link to the Wiki. A little basic, but it helped explain the proprietary nature of "Raw" file formats.
 

Gary RV_Wizard

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I thought that RAW formats were the all the unprocessed pixels, just as the camera recorded them.  Most all the current digitals "process" the pixels to some degree or another to improve image quality and then convert the result to some standard image format and some type/degree of compression. RAW is neither processed nor compressed.

"Processing the pixels" isi the digital equivalent of what the automatic developing systems do to film negatives. They balance colors, lighting, contrast, etc. in an attempt to fix common problems. In doing so, they may eliminate some aspect that the skilled photographer was looking for.  For example, some digital processing will automatically rotate an image, do red-eye correction, adjust facila colrs to a pleasing skin tone. Some digital processors will ieven nterpolate pixels to enhance resolution. If you select RAW format, none of that happens and you can adjust everything yourself with post-processing software such as Photo Shop. Digital cameras witha RAW format usually come with software to handle it, because the pixels in a RAW file are proprietary by definition.

BMP (bitmap) is merely an uncompressed file format but the captured pixels have already been processed.
 

Tom

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Thanks Gary.

I thought that RAW formats were the all the unprocessed pixels, just as the camera recorded them.

That's what I thought, but for some reason I assumed the resulting raw file was a bitmap file.
 

Bob Buchanan

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Tom said:
I'm currently evaluating a couple of cameras before the respective store return policies run out (Since they have different functions I may end up keeping both, but more on that in a different discussion). One of these cameras has options to save images in "uncompressed tiff" or two sizes of jpeg. The same scene produces file sizes of 17.0Mb, 2.90Mb and 1.45Mb respectively. I'm trying to figure out if I'd be missing out on something (in the digital darkroom) by not choosing a camera that saves in "raw" format vs the "uncompressed tiff" format. e.g. your comment ...

"The RAW format allows me to essentially shoot the picture over again in the SW darkroom.

Is this ability lost if the camera saves the images in "uncompressed tiff" format?

From what I know and have read so far, yes, you would be missing out by not having RAW capability. If you do have RAW and want TIFF, you can convert a RAW to TIFF just as you can to other formats via the SW.

I think of TIFF as a super BMP. Unlike the JPEG, it does not lose anything when compressed. It was designed a number of years ago by Aldus for scanning and imaging equipment. It has the nature, as the BMP, of not being machine dependent. However, once in the darkroom, you would be making changes just as you would with a BMP (again, from what I have read and understand so far).

Tho proprietary to each imaging sensor, I understand that some SW (don't know which) will convert various vendor RAW formats. Also, i read somewhere that MS is planning to include RAW software in a future version of Windows. However, as with the Canon, I imagine all vendors with RAW as a format include necessary SW in their kit.

From what I know and have learned so far, I would not want a digital camera that would not give me a RAW format -- as an option. And having the ability to produce both a RAW and JPEG of a single frame is especially nice if that is what I want for a specific shot.
 

Tom

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Bob Buchanan said:
....I would not want a digital camera that would not give me a RAW format -- as an option.

I'm not sure I wanted to hear that Bob as it might influence my final choice of camera. This message might explain a little more of my dilema.
 

Tom

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I moved some of the replies in this topic to here because they really discussed the camera comparisons.
 

Gary RV_Wizard

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but for some reason I assumed the resulting raw file was a bitmap file.

Well, it is a "bit map" per the meaning of the generic  technical term but RAW does not necessarily conform to the Microsoft BMP file format. It's probably pretty similar and in some cases (some camera brands/models) it perhaps can be processed as if it were BMP file. However, it would not assume that to be always the case. RAW is non-standard by definition.
 
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