The digital eye sees things differently

I recently attended a party with my son's playgroup.  After the party, one of the mothers generously gave everyone CDs of the photos her husband had taken with his new digital SLR (dSLR).  As I sat there scanning through the hundreds of photos, it slowly dawned on me that I would not have been able to take the equivalent photos with my digital camera.

The photos from the party were great.  The subjects, almost exclusively one year old babies, were in focus, caught in the moment of smiling, laughing, opening a present, stealing a cupcake, discovering a new toy.  The exposure was good, the colors were crisp, and the backgrounds were pleasingly fuzzy.  Like I said, I couldn't do this with my camera.

What's wrong with my camera.  The short answer is that it is about five years old.  Although has a pleasing feature set for an amateur photographer (also known as an enthusiast), including aperture priority, shutter priority, and manual exposure settings, manual focus, a zoom lens, a flash, a remote control, burst mode (with auto focus - which is increasingly uncommon these days), and spot metering, it is slow.

This is reason #1 why I couldn't have taken the photos; babies don't sit still for very long.  It's something I have been struggling with since my own baby started smiling.  It took weeks of trying before I was able to capture the moment for the grandparents to see.  So I started looking for a new camera (which is part of the reason the blog's been so quiet recently).  With everyone complaining about the slow speed of digital cameras, surely the designers had done something to improve it.

And they have.  I talked to some friends, asked strangers about the cameras they were using, found some reviews (if you're interested in really detailed reviews of digital cameras look at www.dpreview.com), and decided on one I liked.  It was smaller and lighter than my current camera, and it had a 12x optical zoom.  All I needed was to play with one a little to be sure it lived up to its hype, so I made a trip to the local camera shop and had a play.

It was peppy.  It was so much peppier than my current camera.  But my husband thought it could be better, so we asked to see a dSLR for comparison.  Actually, not any dSLR, but the same model used to take the photos at the party.  It was peppy.  It was very peppy.  And after taking a few photos with it, the compact camera felt just as slow the one I had at home.  As we walked out of the store, we concluded our next camera should be a dSLR.

Then we decided they were too expensive.

Since I was stuck with my old camera, I decided to revisit it's functions to make sure I was getting the most out of it.  After the shutter delay, my biggest gripe about my camera is the depth of field.  Imagine complaining about images being too focused, but that's what's been bugging me; I cannot take photos with a shallow depth of field.  This is reason #2 why I could not have taken the photos from the party with my camera.

Shallow depth of field: the subject is well focussed and everything else is blurry.

For those of you who aren't photography buffs, the depth of field of an image is the range of distances from the lens that appear crisp and focused.  It is commonly used to reduce the emphasis on parts of the image that are not relevant.  In the aforementioned pictures of the babies, it was the unfortunate background.  It is also commonly used to give a two dimensional image a three dimensional feel.

The traditional thought about depth of field is that it is inversely proportional to the size of the opening of the lens (aperture) so larger openings yield images with shallower depth of field and smaller openings produce images with more of the image in focus.  Aperture is measured as the ratio of the lens length to the diameter of the opening, therefore a longer lens has a larger opening than a shorter lens at the same aperture number.  The largest lens opening for a lens is always less than the length of the lens, and most lenses are three to five times as long as their largest aperture.

Using the aperture priority mode, I opened the lens as much as possible and took a few photos of my son.  Everything was in focus.  I tried getting closer, so the relative distance to the subject (my son) and the background was greater.  Everything was in focus.  I got even closer.  Now the background was slightly blurry, but still clearly distinguishable, and my son's face was starting to look distorted.  No matter what I did, I couldn't get a satisfyingly shallow depth of field.  Clearly there was more to it than just aperture.

The lens redirects scattered light onto the sensor, shown at left.  A shorter lens (top) makes a smaller image on the sensor, but a smaller sensor means the image can still be framed the same as with a larger lens and sensor combination (bottom).

When investigating digital cameras I came upon the term equivalent length, which means the length of lens on a 35mm camera that would produce the same field of view.  It's only natural that people would be interested in the equivalent length, since prior to the switch to digital cameras, nearly everyone used 35mm cameras and a large proportion of them had a sense of the field of view provided by a 28mm lens versus a 105mm lens.

One camera I looked at had a lens that was equivalent to 35mm at the wide end of its range, but it was actually only 6mm long.  This is accomplished by reducing the format size or sensor.  The image projected onto a small sensor does not need to be as large as the image projected onto a large sensor for the resulting picture to fill the same amount of the frame, so a smaller lens is used with a smaller sensor for equivalent framing. This camera's sensor was only 5.8mm across, or roughly 1/6 of 35mm.  But was this 6mm lens really equivalent to a 35mm lens?

I found a nice explanation of depth of field versus format size at www.wikipedia.com.  The smaller the sensor is, the deeper is the depth of field for a given aperture and equivalent lens length (where the camera is the same distance from the subject and the image is framed the same, assuming the same aspect ratio).

This is a really significant thing for photographers who want to use depth of field to their advantage to consider when selecting a camera.  My digital camera's sensor is 7.2mm across.  That means an image shot at 2 meters from the subject with a 35mm equivalent lens at F2.8 will have a total depth of field (from the near limit to the far limit of acceptable focus) of over 4 meters (according to the depth of field calculator found at www.dpreview.com), whereas with my film SLR it will be about 0.6 meters, and about a third of that with a 4"x5" format camera.  Let's put this into context, if the image is shot in my living room, the background would always be in focus on my digital camera, but nearly always fuzzy on my 35mm film camera.

So when you see a camera spec that states the lens length as 35-135mm equivalent, you should now know that it isn't.  As it turns out, only a few of the most expensive digital SLRs available on the market today have a sensor as large as 35mm film.  The vast majority of consumer digital cameras (as opposed to professional digital cameras) have sensors between 1/9th and 1/3rd as large.

Incidentally, I've just recently started getting prints of my digital photos and have discovered that they all have a blue cast (well, really it's cyan).  That's reason #3 I couldn't have taken the photos from the party.  Maybe I will get a new camera soon.

The death of free to air?

As mentioned in a previous post, I gave up watching TV.  There was a caveat, that I would watch one or two of the best shows (where "best" is entirely subjective).  Well, the new season has rolled around and the TV is still off, but the VCR is working pretty hard.  I've got it recording the one or two best shows every week and now have eight weeks of them on tape with the intention of watching them when I feel like watching TV.  So far, I've watched one hour.

Now, it doesn't take a genius to figure out that this is going to become a horrible mess, even with just two shows, trying to keep track of what's been watched and what hasn't, making sure the tape in the VCR has enough capacity, and is positioned in the right spot.  But technology comes to the rescue (or would, if I were earning money and could justify the expense) in the form of a digital video recorder (DVR).  Many of these little units (often paired with a DVD recorder) can record up to a hundred hours of TV, and allow you to pause and rewind live TV or start watching a show already in progress from the beginning while still recording the end, instantly navigate through your recordings by means of a menu (rather than having to scan through hours of programs to find the right spot), automatically select items to record using a broadcast guide, and provide a commercial skip function.  Why has it taken so long for these to be widely available?

Now, the commercial skip function is not a new idea.  It is nothing more than a 30 second fast forward that can be repeated a number of times and exists on my five year old Korean VCR.  The difference is that with digital content, it is possible to instantly skip an entire ad break of predictable length without even scanning the ads in fast motion.  Television broadcasters will have to become increasingly clever to force people to watch at least some of the ads.  My guess is that the length of ad breaks will vary more and shows will be scripted so that there can be more ad breaks.  There will be a premium on the last ad space in a break (or perhaps the last few in a longer break) as the first few will be able to be skipped more readily than the last without missing the return of the show.

As fewer people see the ads, they will become less useful marketing tools, and networks will have to become more creative about how to pay for the cost of purchasing or creating shows and delivering them to viewers.  Advertising will become increasingly insidious and difficult to avoid.  Shows will decrease in quality as they incorporate product placement to pay the bills, as seen in "The Truman Show" or "Survivor".

As people can watch whenever they want (after the initial broadcast) networks will no longer be able to use high profile shows to increase the viewership of the duds placed between them.  Whereas we may brighten up at the prospect of fewer bad TV shows, the reality is that there will be fewer good TV shows, because they are the ones that cost money to produce.  I suspect this will force free to air networks out of business or searching for a new profit model that includes either a subscription price (as with cable or satellite TV) or pay per view.

For those of you living in the US, the TiVo has been around for quite some time and provides the functions described above for a subscription.  In many areas of the US high proportions of people already subscribe to cable TV due to poor reception.  Not so in Australia, where cable TV does not include the free to air networks, but with only 2-6 free to air stations, depending on where you live in Australia, many people subscribe to cable just to have more choice.  My guess is that the growing availability of DVRs will be the death of commercial free to air TV.