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.
