White Egret
What is the problem with Point & Shoots?
Point and Shoot cameras (P&S) have a number of defects and many of them can be traced to the small sensor size in the bodies. A DSLR sensor is about the size of a large postage stamp but P&S sensors are the size of a fingernail. Those tiny sensors have just as many pixels squeezed onto them as the larger DSLR sensors have. That means the pixels are tiny and very close together. Sean McHugh explains this in more detail. Roger Clark goes into great technical detail about this issue on his website. Some of the problems caused by these small sensors:
- High apparent noise level and diminished ISO
- Loss of Depth of Field Control
- Decreased dynamic range
The high noise apparent noise (see below for a comment from Roger Clark) level of these small sensors mean that even tho the camera manufacturers may show higher ISO values in the camera controls those high ISO values are unusable.
Depth of Field (DOF) is how photographers control the zone of sharp focus in an image. It is one of most important creative factors that photographer use to control what the viewers see. A photographer can show a person in sharp focus but throw everything behind that person out of focus and thus concentrate the viewer’s attention on the subject and not the background. And because of the physics of small sensors and the lenses that they use on those cameras you are unable to control DOF. Everything in the image will be in focus, period.
(Note on this: see below for a comment from Roger Clark)
You can see this for yourself by playing with this calculator. For example at 55mm and at f/4 a Canon DSLR has a zone of focus of 1.1 feet at a distance of 10 feet. A Nikon Coolpix P90 has an infinite zone of focus. When you use this calculator you need the real focal length of your camera’s lens not the 35mm equivalent. Usually dividing the shown focal length by 8 or 10 will get you in the ball park. So a P&S that show 60mm is probably actually around 6 or 7 mm in reality.
The dynamic range (DR) of an image is how much difference exists between the deepest blacks and the brightest whites that the image will show. DSLR cameras with 14 bit processors will have a distinctly higher DR at low ISO and will maintain higher DR all the way thru their usable ISO range. P&S cameras start of with lower DR at low ISO and this drops rapidly as the ISO is increased.
Other defects
Some other defects of P&S cameras are:
- They limit the user to jpeg files
- They have small memory buffers
- They use a slow focusing mechanism for the lens
- The camera processors are slow
- They have long shutter delays
- They use up batteries quickly
DSLR cameras can use raw format for the image files. These raw files have many advantages. Too many to go into here but they are a vast benefit to serious photographers. Michael Reichmann’s Luminous Landscape has a good article on the subject. There were a few P&S cameras that allowed the use of raw format but manufacturers have mostly eliminated that feature on most of them. The only apparent reason would be to drive people to buy a DSLR to get raw. P&S cameras all capture the image in raw but convert the raw images to jpeg before you can get to the file.
There are actually people who hack the firmware on cameras to add raw capability and I notice there is a list on Yahoo devoted to that subject. I have been a bit perplexed by those hackers since I don’t know what you could do with a P&S raw file. Raw files are not images, they are the actual data that the camera sensor captured. A raw file converter takes that file and converts it to a real image. But no commercial converter software will take any of those P&S raw files.
A memory buffer is where the camera stores the file until it is fully written to the flash card. DSLR can often hold 20 or more images in a buffer but P&S are lucky to hold a couple of files.
DSLR cameras use a lens focus method that depends on the camera having a mirror, called phase detection, P&S cameras have no mirror and are stuck with a much slower method called contrast detection.
DSLR cameras use a fast processor, sometimes involving dual processors that are much more powerful that the microbrains used in P&S cameras. And of course they can make use of the much greater amount of memory in the camera.
All the points above are the cause of one of the major points of irritation on P&S cameras. The very long period of time that elapses between the time the shutter button is pressed and the camera actually takes a photograph. On some of the worst examples this can be one full second. And by the time the camera actually makes a photograph that special thing that junior was doing is only a memory. This is called shutter lag.
The shutter lag on DSLR bodies is usually around 0.05 seconds or so. Pressing the shutter button most of the time fires the shutter instantly. This comes from the fast focusing lens, the fast processor and for multiple shots the big buffer. Current DSLR cameras can shoot somewhere between three and ten shots every second. And keep that up until 20 or more shots have been captured. Something between a half of a second and one and a half seconds to capture five shots. A P&S takes between six seconds and 25 seconds to capture 5 shots.
And last thing I’ll mention is the incredible way P&S cameras eat batteries. A DSLR will be able to take thousands of shots on one battery charge. The batteries last for days or weeks depending on how many shots you take. My sons Canon G series camera uses the same type of battery as my Canon 40D and he is using the battery charger all the time. The 40D body is much larger than the G and the lenses are vastly larger and heavier and move faster but the batteries last much longer. I doubt he can get 200 shots on a charge. And that camera is no different than other point and shoots in that respect. I don’t know why it is, perhaps running the LCD kills the battery. But they go fast.
Should most users move to DSLRs?
In my opinion and despite all the advantages of a DSLR, I think the answer is no. DSLRs are darned hard to use, the manuals are thick and you cannot ignore what is in them. Manufacturers add all sorts of ‘shooting modes’ to the lower end DSLRs to try to pretend that these are super P&S cameras but they are not. And many people who buy them expecting that they can continue their point and shoot practices are soon unhappy with their new and expensive DSLR.
I often hear complaints by new DSLR owners that their cameras are producing ‘bad’ images. Well the images are fine but the DSLR user has to understand how to make good images, he has to do a lot more thinking and has to understand photographic technique. Plus most DSLR images need post processing, you have to learn how to use Photoshop Elements or even Photoshop (there are a lot of other software packages out there) to make great photographs.
And obvious solution to the problem of people wanting something better than a P&S and the complexity of DSLRs would be a automated camera with a large aps-c sized sensors and LCD focusing. People have been calling for this type of camera for years. But no manufacturer will make one. It is a mystery, perhaps DSLR manufacturers do not want to introduce a model that would compete with their DSLRs. But there are camera companies that do not make DSLRs or if they do sell darned few of them. Why don’t they produce such a model?
If you are serious about being a better photographer, then of course a DSLR is the only way to go in their price range right now. But be prepared to work hard to master the camera, read the manual, buy a book or two and shoot a few 1000 shots before you begin to get a good feel for using the camera. Having a background in film SLR cameras will make the switch easier but it will still be difficult.
Next up: comparing DSLR systems
—UPDATE—
Roger Clark has this comment:
“The correct way to put this is that the small sensors actually have LESS noise
at all levels, from shadows to highlights. The problem is that the small pixels collect so little light that they have very LOW SIGNAL. The factor that we see in images is not absolute noise but signal-to-noise ratio. So the small pixel cameras have low signal-to-noise ratio at all levels from shadows to highlights compared to the larger pixel DSLRs.”use that link to his site above to get a much fuller discussion of this.
