Number 228 - May 2002

Some Thoughts about Digital Cameras
by Alex Dumestre, 1960 PC User Group
I was musing recently about the rapidity with which the digital camera scene is changing. In general, things are getting bigger, better and cheaper. You can't complain about that can you? But these changes can create problems unless you can change the way you think about some things - and unless your computer system keeps up with the increased demands placed upon it. Resolution, for instance     The name of the game is resolution. As recently as four years ago affordable digital cameras were advertised as having VGA resolution! If you have been around PCs for a decade or so you might recognize VGA (Video Graphics Array) as referring to some of the earlier monitors that were capable of displaying 640 x 480 pixels, the state of the art in 1990. A camera that could take a picture that could fill up a VGA monitor screen was then the goal of most camera makers targeting the consumer market. VGA is less than one third of a megapixel (640 x 480 = 307,200). Pictures of this resolution were suitable only for display on a monitor or as prints no larger than 4" x 3". That didn't make digital cameras appeal to very many people, particularly when their prices were in the $500 - $1000 range. Soon the cameras had advanced to SVGA (Super VGA) resolution which is 800 x 600 pixels. This is in the half-megapixel range.     Then, about 3 or 4 years ago, the advertising was touting Megapixel cameras. These came with prices of $1000 +/- a couple of hundred bucks. The first digital camera that I got my hands on was a 1.3 megapixel beauty by Olympus. This was a point and shoot camera that could provide decent 5" x 3" prints and was a joy to use but the price scared me (and most people) away. Then, about 2 years ago I tried out a 2.1 megapixel camera and found that I just had to have it.     Since then we have seen an increase in megapixel size every few months, stepping up through 3, 4 and 5 megapixels until today we are seeing 6 megapixel cameras being advertised to consumers. And the amazing thing is that each time the megapixel size is increased the price remains about the same - in the $600 to $1000 range. (In all of the cases that I'm talking about I assume the camera is a name-brand, quality camera with a good zoom lens and automatic everything with some manual overrides - what the industry refers to as Point and Shoot). Even better news is that last year's models are quickly moved into the sub-$500 price range and that can really be a good buy. So where's the problem?     Is it possible to have too much of a good thing? Well, sometimes it can be a problem. One of the first things to consider is storage space - both in-camera and computer-related. As recently as two or three years ago one of the most popular digital cameras was the Sony Mavica that captured its pictures directly to a built-in floppy disk. This was a wonderful approach back in SVGA days because one could fit several of the half-megapixel images on a floppy, perhaps enough for a day's worth of picture taking. Even if a floppy won't hold very many pictures, they are plenty cheap and very available. You could do such things as ask a stranger to take a picture of you and the family at the Grand Canyon with your camera and then, instead of just saying thank you, turn around and take a picture of him and his family and hand him the floppy! And when you (or he) got home you just inserted the floppy into your computer. What download problem?     Let's take a little detour here. Don't confuse a megapixel with a megabyte. In some cases they can be numerically similar but in most cases they are two different animals. A pixel is a tiny area of color on a picture which is stored as a code number in an image file. In order for pixels to form wonderful, sharp, clear, photo-realistic images there must be hundreds of thousands or millions of them. That means that a raw image file must store hundreds of thousands or millions of numbers. How much memory does it take to store one of these numbers? A byte? Not unless you are satisfied with only 256 colors. For real color we usually demand 16.7 million colors (24 bit/pixel TrueColor). Twenty four bits require three 8-bit bytes. So, even an SVGA image that is approximately a half-megapixel requires a raw image file three times that size or approximately 1.5 megabytes!     Wait a minute, how do we fit even a single 1.5 MB raw image file on a 1.44 MB floppy disk. The answer is that we don't--not without compression. The vast majority of digital pictures are written by the camera to its storage media (Memory Stick, CompactFlash, SmartMedia, floppy, ZIP, Mini CD-R, MicroDrive or whatever) as a compressed JPEG file. A high-quality JPEG is, perhaps, only one tenth the size of the raw image file and therefore we can fit up to ten SVGA resolution images on a floppy. How many 2 MPix compressed images can fit? Only two or three. How many 6 MPix JPEG compressed images will fit? None! The days of the floppy drive camera are numbered.     The obvious observation is that as MPix ratings of cameras climb, so must the size of camera storage media. Luckily this is happening and card and stick RAM is becoming cheaper and cheaper. 128 MB cards cost what 8 MB cards cost two years ago and cards, MicroDrives and Mini CD-R disks are exceeding the 200 MB size. Computer Considerations     Not only must these huge image files be stored on the camera but they must also be downloaded to the computer and processed there and they must be archived and backed up. I just came back from a 16 day vacation with almost a GB of compressed image files. Back in the days of 4 GB hard drives this would have presented a problem but with today's 80 GB hard drives it has almost disappeared as a concern. In the days of archiving to ZIP cartridges, these large images would have run me broke but with today's CD burners it is a non-problem.	With size goes a need for more speed - in downloading from camera, uploading to Web, processing with graphic editors, etc. If you get into working with multi-MPix camera images and doing editing on them then you will need a muscle computer that used to be considered necessary only for serious gamers. We are talking GHz processors and 256+ MB of RAM and don't even think of trying to use parallel or serial ports for downloading from camera. Luckily today's USB is adequate and tomorrow's USB-2 will be even better. Not until you get into video editing will you have to have firewire. It is evident that the PC is keeping up with the needs of digital camera fans but you, personally, may have to replace that 66 MHz Pentium with 500 MB hard drive that has served you well these past several years. So how much resolution do you need in a camera?     That depends on a lot of things - mainly on the depth of your interest in photography and how you use the photos that you take. If you are serious about photos and proudly hang 14" x 11" enlargements on your wall and want to be able to read the licence plate number of a car in your picture that was three blocks away then you might really need a 5 or 6 MPix camera. If you shoot vacation pictures and family birthday parties and e-mail these to friends and store the resulting prints in a box and carry around a stack of wallet sized pictures of the kids (or even print an occasional 8" x 10" to frame) then you can probably be quite happy with a 2 or 3 MPix camera. Why go to the trouble and expense of creating huge image files for uses that do not justify it? You might be better off spending the extra money on a better lens or fancier controls. If, on the other hand, you are a real photo hobbyist and you can afford it then, what the heck? Go for it. Selectable Resolution     You should realize that just because you have a 4 MPix camera that you don't necessarily have to take all your pictures at the full 4 MPix. All of the cameras may be set to take pictures as something less than their maximum resolution. This is useful if you know that the particular picture-taking session does not require the highest resolution and you want to fit as many pictures as possible on your card. Think carefully about this before using it. You can always convert your high resolution images to lower resolution but you can never go the other way. E-Mail     It is not uncommon for newcomers to buy a nice new multi-MPix camera, snap a few pictures of the kids and immediately e-mail a couple of dozen of them to everyone they know. If they have a dial-up connection, they will soon realize that this is not the thing to do but if they have broadband but some of their friends have dial-up then they will have to rely on them (or their ISPs) to tell them. Someone sent me two 4 MB image files the other day that caused two things to happen. 1) when I checked my mail the message was truncated after a few lines followed by a note from my mail server that the remaining 8MB would be downloaded only if specifically asked for it. 2) I received an e-mail from my ISP informing me that my allotted 10 MB of e-mail storage space was 87% full!     The considerate thing to do is to make a reduced resolution copy of the original to be used as an e-mail attachment. My standard practice is to reduce copies to 640 x 480 pixels from their original 1600 x 1200 (or whatever), convert them to JPEG, if they are not already in that format, and send them on their way. These are typically in the order of 50 to 90 KB in size and take well under a minute to transmit over dial-up lines. They are large enough to fill the screen, or at least a sizable portion of it, on most people's monitors and don't usually have to be scrolled to see the whole thing. These, however, do not have adequate resolution to allow the recipient to make a decent print much larger than wallet size. No problem, if the recipient thinks the picture is just adorable, you can always e-mail that one to that person in a more suitable resolution and know that the 10-minute download time is appreciated and not resented. One last caveat on this subject. Make a reduced resolution copy. Do not apply the reduction to your original. You can't go back. The Future     So far the flow of change has been such that I've been able to slowly adjust my routine to keep abreast of the changing technology. This may not last much longer, however. I've typically converted my photo files from JPEG to TIFF if I wanted to do much editing on them. Once finished with the editing I then convert them back to JPEG in order to save storage space - the TIFF is generally about 8 times larger than the JPEG. Both file types are compressed compared to the original raw file but JPEG achieves its much smaller file size at some cost in quality while the TIFF causes no reduction in quality. The JPEG lossy compression is generally acceptable unless it is redone several times, so that is the reason for not using JPEG during repeated editing/writing passes. So what changes do I foresee in my operating procedure?     One is that today's huge hard drives hardly require that I be stingy with the file size so maybe I should convert all of my new shots to TIFF and leave them that way. On the other hand, I would only be able to fit perhaps 200 pictures on a CD instead of the 1500 - 1600 that I currently get.     If the long awaited JPEG2000 finally becomes widespread this year then I'll just start using it and forget about the TIFF intermediate format. Why? Because JPEG2000 can achieve 100 times the compression of TIFF with only an imperceptible loss of quality. Ah, progress!     Alex Dumestre has been associated with computers since the mid '60's, most of the time developing geophysical applications for use on mainframes, minicomputers, and work stations. He is a bit of a nut about graphics but is a perpetual novice on PCs. He is a member of the 1960 PC Users Group and can be contacted by e-mail at DumestreA@PDQ.net
Number 228 - May 2002