Choosing a Digital Camera

An Educated Layman's Guide

For many years you've enjoyed the "traditional" (i.e., film-based) photography, getting decent (or better) pictures and lots of satisfaction ó both from the process itself and from the results. If it ain't broke, why fix it?

Still, for one reason or another you are tempted to try the digital medium. Maybe you have read my previous Quest article and decided to prove me wrong at your own expense, maybe you just want to see whatís on the other side of the fence. You are ready to try a trip into the digital domain, and the first step is to acquire a digital camera.

Not really. Actually, you may keep shooting slides or negatives, scanning them and then tweaking the results digitally to your heartís desire. Many people do that; so was I for a couple of years, until I discovered that a semi-decent digital camera usually brings better results. If you are reading this, however, it means you have either tried or rejected this option already.

So here it comes: advice for photographers (as opposed to gadget lovers) who need to choose from hundreds of digital models available on the market.

This, obviously, is not a comprehensive review of all possibilities, but rather an overview of things to keep in mind when making your own educated choice.

What kind of a camera do you need?

Very much like in the 35-mm world, digital cameras can be categorized into a number of distinct breeds. This can be done in a number of ways; my taxonomy runs by viewing system and, to an extent, by the form factor and size.

The models shown here are not necessarily my selections, they are shown only as examples of cameras in each class. My (possibly opinionated) recommendations in each group will be presented only in the next article of this series.

No optical viewfinder, compact size.

These are closer to electronic gadgets than to cameras, with viewing only via an LCD monitor on the camera back. The monitor, in addition to limited resolution, is often not very readable in daylight (although much progress was done in the last year). I consider this kind unacceptable for anyone who is likely to read these pages. Enough said.

The upcoming Stylus (Mju) 500 Digital from Olympus is a good example of a camera in this group. Although loaded with features (including 2.5" LCD display with >200k pixels), it lacks an optical viewfinder, and the tiny image sensor may make image quality not good enough for any semi-serious uses. Both disadvantages are common to all cameras in this class.

(The camera does not seem to have much in common with the previous digital Stylus models; an example of name recycling.)

Optical viewfinder, compact size.

These are cameras you can carry around all the time, usually fitting into a pocket or a purse. If you are not sure you want to go digital, this kind may be a good choice ó at least as a backup camera for your SLR. The optical, zooming viewfinder usually leaves a lot to be desired, but for critical uses like close-up photography, you can always resort to the LCD monitor.

For portability, the compacts are often built in the clamshell form factor, with the lens mounted within a collapsible barrel. Some, while not using the clamshell solution, still have a telescoping lens behind a protective external diaphragm. In extreme cases, the barrel may have three parts, and some lens elements may be moved aside when it is in the collapsed state. Ingenious, but not very sound mechanically.

A serious user would opt for the larger and heavier end of this range, as this is usually correlated with lens quality and more control options (like shutter and aperture priority, exposure compensation, etc.)

A good example of a tiny, yet very capable camera in this class: the Olympus C-60 (a.k.a X-3). The degree of control should satisfy a demanding amateur, while the image quality is also quite good.

Be warned, however, that while many cameras in this group look quite similar, the specifications, image quality, and control range may differ dramatically from model to model, so that great caution is needed when making your choice.

Optical viewfinder, regular size.

These cameras, while still providing an optical viewfinder, are not pocketable, reminding to a large extent the classic rangefinder models of years past. The lens, while usually collapsible, does not fold flush with the body, and offers better specs and quality.

Most of these models offer the full range of manual adjustments and automation overrides; they also accept various accessories, most notably an external flash and lens attachments.

This is why these cameras are a frequent choice for a serious amateur who for some reasons (weight, cost, convenience) may be unwilling to opt for a digital SLR.

A good example of a recent camera in this class is the Canon Powershot G6 of 2004. It continues the tradition of Canon G-models, at the same time changing the camera appearance so that it is now similar to that of competing Nikon and Olympus models. Seven megapixels may be an overkill for this sensor size, but the lens is excellent.

Similar models from Nikon or Olympus show very similar specifications and features; all also accept quality lens attachments extending the focal lenght in both directions.

Electronic viewfinder.

These cameras (often referred to as EVF models) usually are equipped with a wide-range zoom, with the longest-to-shortest focal length ratio between 1:6 and 1:10, sometimes with electronic image stabilization. Building an optical finder for these ratios is not simple, and I suspect this was the main reason behind the EVF solution.

In my opinion (supported with a casual experience with some of these models) these cameras are addressing rather the gadget-loverís than photographerís market. Especially in the U.S., where the mass market is largely specs-driven, eight is better than six, whatever these numbers may denote, and I have seen my share of badly focused and shaken images from EVF cameras of excellent specs.

Besides, it is quite difficult to take a good picture if you cannot see your frame well, and electronic viewfinders are still plagued by low resolution, shakiness, and flat tonal range. Every time Iím tempted to buy an EVF camera, I take one look through the finder and decide to wait another two years, maybe more. It may be personal, but I canít take pictures, while composing them on a low-quality TV screen.

With all my dislike for EVF cameras, I must admit thet the 8MP Minolta (pardon, Konica Minolta) DiMAGE A2 has very enticing specs, starting from a great lens and ending with a high-resolution (one megapixel!) electronic viewfinder, better than any competition I've seen yet.

Still, every major manufacturer has at least one model in this category, and all of them are packed with features, aimed at techies among us. Maybe one day I will warm up to these cameras, but not any time soon.

Single-Lens Reflex.

As with film cameras, this class is the most frequent (although not the only) choice for a serious user. Try an EVF camera, and then an SLR and you will see why.

Until two years ago, digital SLRs were, indeed, Ruby Goldberg contraptions, hybrids of a modified film camera body with a digital circuitry (each part even had its own power supply). They were also outrageously expensive.

Things changed. After the revolutionary E-10 by Olympus (which used a beam-splitting prism instead of the classic mirror), some other makers, most notably Canon and Nikon, released well-rounded models capable of satisfying the most demanding user. The new models offer lens interchangeability, impressive specs and good performance ó at the expense of extra bulk and weight.

As an example, the Olympus E-1 is the first interchangeable-lens SLR built from the ground up in the best Olympus tradition of innovation on one hand, and perfectionism on the other.

While some may complain about "only" five megapixels of image resolution, the camera delivers outstanding results, at the same time being a delight to handle. (A simpler, 8MP model, Olympus E-300 goes on sale this December, at half of the E-1's price to satisfy those who insist on pixel-counting.)

Canon, Nikon, and Pentax also have similar cameras at similar prices, and all of them have a dedicated following.

Specs and Performance

You may think that these two aspects are closely related, but this is not always the case. Camera sales are driven by the mass market, and that is dominated nowadays by illiterates. I know this is not a nice thing to say, but I owe you the truth: just check some questions (and, worse, answers) in many Internet discussion groups, and you may see my opinion as rather understated.

Camera makers seem to be quite happy with this state of affairs: an educated customer may be more demanding, while an ignorant one will buy whatever they put their advertising dollar (yen, pound) into.

Eight megapixels must be better than six, eight-times zoom ratio must be better than six times ó have you noticed that the lens aperture is never shown in any camera ads? How can you sell anything by a virtue of a lower number?

My vitriolic outburst aside, let us see what to look for when choosing a camera, not necessarily in the order of decreasing importance.

The Lens

In film cameras of yesteryear, the lens used to be the most important factor. Yes, you needed a shutter and a winding mechanism, but the picture quality was decided between the lens and the film (plus, of course, the printing process).

Not any longer. When you buy a digital camera, you are also buying the lifetime supply of what used to be film: the mechanism to translate the incoming optical image into the image record, and, indirectly, into the final picture as you see it afterwards.

Until a few years ago the cameraís light sensor, or the "electronic film", used to be the limiting factor of image quality. Almost any lens would do. Digital imaging is, however, progressing, and, while the sensor is still important, the lens is regaining its significance in the overall results.

Did I mention the mass market before? More often then not, the only question a buyer is asking (and the only specs the maker is pushing) is the zoom range, or, at least on the American market, "how many exes does the lens have" (my British readers may think Iím joking, but Iím not).

While the zoom lens ratio is an important convenience factor, it is not the only one. Usually a 3:1 or 4:1 zoom is enough for most uses; and one should look at some other aspects.

  • What is the widest lens angle? While most tyros do not care about this feature, you do. Most non-interchangeable camera lenses start at 35 mm EFL (equivalent focal length, i.e., the focal length of a 35-mm film camera lens, providing the same image angle); some start at 38 mm. Very few go down to 28 mm, providing a very nice wide-angle capability for interior and landscape shooting ó anything shorter means venturing into semi-exotic territory.

    The wider the zoom angle, the more expensive the zoom lens gets. It is much cheaper to make a 35-140 mm EFL lens, than a 28-112 mm one of a comparable quality, while both retain the same 4:1 zoom ratio. Guess what camera makers want to sell.

  • What is the lens maximum aperture? Another place to cut corners, especially at longer focal lengths. Wider aperture allows to shoot at faster shutter speeds and/or lower sensor gains (less electronic noise), in addition allowing for greater degree of control over depth of field.

    Except for the compact class, I would recommend looking for a lens with not more than one F-stop of difference between the wide and tele ends. Camera makers, however, often feel they can get away with more ó and they do.

  • Does the lens offer full aperture adjustment? Some of the cheaper cameras in the compact class allow you only to set the maximum and minimum aperture, and nothing in-between. For many uses this may be not acceptable, although it may be OK for vacation snapshots.
  • How good is the lens optically? Just last month, while choosing a compact camera for my wife, I went through image samples from no less than 26 models in that class. Many were simply unsharp (and not just in the corners), some suffered from chromatic aberration (sometimes in addition to color fringing, a similar effect due to charge spillover in the sensor), and most had visible vignetting, i.e., loss of light in image corners.

    This is not something you will see in the specs; neither should you depend on a reviewerís (or mine) verbal description ó go out to the Net and see the samples by yourself. The most dependable source of well-shot, consistent image samples I can name is the Steveís Digicams site. (Just ignore rephrased manufacturerís blurb in the reviews themselves, and youíll be fine.)

    Obviously, the samples show the combined effect of both the lens and digital image capture/processing, but do not make a decision without a close look.

  • How is the zooming done? Aside from SLRs, in most cameras you zoom by pressing a button or pulling a lever. This solution, while often necessitated by the collapsible lens construction, is much less precise than a ring around the lens.

    Be aware that some EVF cameras provide electronically-controlled zooming via such a ring; nicer than a button, but still less precise than a mechanical link.

The Megapixel Myth

The first question many people would ask about a camera is: how many megapixels. How wrong. Did I mention the mass market?

With the sensor technology geared for mass production, it is cheaper to throw in an extra megapixel or two, then to provide two extra buttons to access some frequently-needed features.

Actually, a six-megapixel camera collects only about two megapixels worth of information, as for every image pixel it uses just one RGB component signal, interpolating two other components from the neighbouring photosites. This is interesting enough for a separate article.

From my own experience, 3MP is enough to provide beautiful prints up to 18x24 cm (even from cropped frames), and acceptable ones at 22.5x30 cm. My wife had gorgeous 15x20 cm prints from her humble 2MP Olympus. And I am not easy to please.

For a serious user, five megapixels is certainly enough ó if the lens is able to provide enough resolution, and more often than not, it isnít. Anything else only takes room on the memory card, and slows down image processing. Well, maybe an SLR with high-quality lenses (like the Olympus E-1) could use more than 5MP, but even here I am not quite sure.

Color Depth and Image Storage

A feature usually overlooked is the color depth of the image: how many bits are being used to store a single RGB component of a pixel. While the common JPEG standard is limited to eight bits (256 levels) per color, many cameras allow you to store images in the raw format, as taken from the sensor. If that format has more pixels per color, you have a larger dynamic range, being able to retrieve detail from highlights or shadows more easily.

Most cameras record ten bits per pixel, better ones ó twelve, and a few ó fourteen. Keep that in mind, although you will not find the data in most reviews.

A related issue is that of image file format. The predominant standard is JPEG, a scheme using a lossy compression to reduce the file size from (usually) four to twelve times. Greater compression saves space, but introduces some image artifacts. Most cameras allow you to choose out of two compression ratios, usually referred to as high and super high quality, which, of course, means nothing.

Some cameras also offer the lossless TIFF compression scheme. Being limited to eight bits per color, it does not offer practically any advantage over a lower-compression JPEG. I have used the TIFF format just a couple of times, trying to spot the difference.

As mentioned above, better models allow you also to store images raw, just as they were taken off the sensor, i.e., without any adjustments and color component interpolation. In theory, this may come handy for a discerning user who may want to do some critical adjustments before any information is lost in translation. As tempting as this option may be, Iíve given up on using it: other factors seem to be more critical for the final results. Your experience may differ.

Sensor type

Most of digital cameras use CCD (charge-coupled device) sensors, first used in astronomic imaging decades ago; some use another technology, referred to as CMOS. While initially CMOS sensors exhibited more noise than CCDs, at this moment both kinds are capable of delivering equally good results, so the type of the sensor should not be a factor in choosing a camera.

A sensor consists of individual photosites, each responding electrically to light reaching it. The photosites are color-blind, therefore each of them has a small color filter on top of it, making it effectively sensitive to just one RGB component. The manufacturers like to refer to photosites as pixels, although this is not quite true, as I already mentioned above.

Really, in most sensors for every red and blue photosite there are two green ones, but this is just a technicality. Also, Sony is touting their new approach with four different sensors in a set, adding emerald to the three basic colors. As a physicist, I yet have to be convinced.

A notable exception to the standard solution is the sigma SA model line, with each photosite consisting of three "vertically" placed sensors. These cameras were originally advertised as 3-megapixel ones, now Sigma is referring to them as 9-megapixel. True, a standard 9-megapixel sensor would have as many sensors as a Sigmaís 3-megapixel one, so now at least everyone is bending the truth the same way.

All cameras allow for adjusting the amplification (or "gain") of the signal collected from the sensor, therefore effectively increasing the "film speed". This is expressed in the equivalent-exposure ISO film speed setting. Raising the gain usually leads to increase in image noise, quite similar to film grain.

All big-name cameras I have tried in the last two years had image noise which was at least acceptable, comparable or better than the grain in an ISO 100 negative film. At higher gains (ISO settings) the noise may be less acceptable; in some models becoming somewhat objectionable as low as at ISO 200.

Most reviews I have read, however, seemed to be too fussy about the noise issue, and I suspect the writers might have never seen a film image enlarged to the same screen size as their samples. We have to remember that viewing a pixel image on a computer screen in full size tends to exaggerate the noise effect.

The noise is, again, enough of a subject for a separate discussion, let me only say that noise-reducing algorithms are used in all cameras, regardless whether this is advertised or not. (The "noise reduction" you can sometimes see in the specs refers to the static noise reduction, applicable only at exposures of one second and longer.)

In-camera image processing

The image taken off the sensor is (except for the raw storage mode) not written directly to the memory card. Before that, it undergoes quite a lot of processing, which takes both time and energy (battery juice). Let me mention the most obvious steps, not necessarily in chronological order.

  • First of all, for every pixel the missing color components have to be interpolated from the neighbours. This was covered in the previous sections.
  • The color balance of the image is adjusted. Actually, most cameras do a very good job in that, so that in effect you have both daylight and tungsten film in your camera, no need for corrective filters. Many cameras allow you to set the color balance manually to one of the available presets (or color temperature values), some also offer setting "by reference".

    In the latter mode, you point the lens towards a white (or neutral-gray) area and press a button (more often, a combination of those), which means "I want this to be neutral". Iíve used this approach with a number of Olympus cameras (excluding the E-10 and E-20, where the feature did not seem to work at all), and the results were always first-class, better than any presets or the automated choice.

  • Sharpness, contrast, and color saturation adjustment. These are performed, seemingly, to make the images more "pleasing", often with mixed results. Most often I have issues with image sharpening.

    You cannot add detail where it was not captured, and it is very easy to have the image oversharpened, with white fringes along high-contrast boundaries. While this may look "sharp" in a mass-market, postcard-sized print, at any larger size it is quite an ugly effect, a sign of manufacturerís bad judgment.

    Luckily, the degree of these three adjustments can be changed in most cameras Iíve tried (except for the most basic ones). Many users would never think about it, but you should. Make sure your chosen model has this feature ó it is much more essential than a 10:1 zoom.

Autofocus

Letís face it: you have to have it, and you have to use it in any digital camera (except, maybe, SLR ones). Except for the SLRs, autofocus is performed based on the signal from the same sensor which is used to capture the image, and this may be the reason why the AF capabilities of digital cameras lag behind the film ones, in terms of both accuracy and speed.

On the other hand, digital non-SLR cameras are much more tolerant to focusing errors than film cameras. This is a matter of sensor size; for example, a digital model with the sensor being 7 mm across, at F/2 will provide the effective depth of field equivalent to a 35 mm film camera at F/10 (assuming the same effective focal length, or image angle).

Some cameras also allow you to switch to manual focusing. While this is not of practical (or precise, with a tiny distance scale on the LCD) without SLR viewing, the feature may be used for no-focus shooting, with the depth of field taking care of varying subject distances, especially at shorter focal lengths.

The Viewfinder

Iíve discussed this issue in the beginning of this article, so you know what the choices are. And, obviously, an SLR finder is my first choice, while an EVF ó a distant last. Thus, let me focus on the middle ground: optical viewfinders.

I have no good news here: in all digital cameras Iíve tried, optical viewfinders range from bad to very bad (although not as bad as in the Soviet Leica copies from the Fifties and Sixties). And you cannot take a good picture without seeing what you are shooting, period.

First, they do not show, even approximately, the whole scene which will be in the image. When a manufacturer claims an 80% coverage, they really mean 64% of the area, as the given percentage is linear. This means that you do not see 36% of what will be in the picture. Try for comparison a Japanese rangefinder from the Seventies (or the East-German Werra, a very collectible model), and you will see. It is understandable that a zooming finder is more difficult to make than a fixed-angle one, but still.

There are also large differences in the finder magnification. The market does not seem to care; during the recent research Iíve noticed that a newer compact model by Nikon has a smaller finder than the model it replaced, with both cameras being almost identical otherwise (oh, well, more megapixels, who cares?).

Last but not least, many models omit the eyepiece diopter adjustment.

In any case, even if a review says "brilliant optical viewfinder", do not trust that. Try before you buy.

The Shutter

Some digital cameras have a shutter, and some (especially the less expensive ones) do not. Instead, they rely on electronic circuitry to limit the time during which the image signal is collected on the sensor.

A "real" shutter provides, due to many reasons, better results. It is, however, more costly, being quite complicated, at least in non-SLR models. Instead of a simple open-close cycle like in film cameras, such a shutter has to stay open, letting the light through to allow for electronic viewing, exposure metering, and autofocusing. When the release button is pressed, all this ceases, the shutter closes, the image sensor is flushed ó only then the shutter opens to take the picture, just to close and reopen again. Quite a convoluted process; no wonder the response of most digital cameras is quite sluggish.

SLRs (except for the older Olympus E-10/E-20) use separate circuitry to do all the extra processing, therefore being more responsive (and more expensive, too). They are, however, plagued by other issues, including the problem of dust settling on the image sensor, some of that dust coming from the focal-plane shutter used. There are no free lunches.

As for the range of shutter speeds, even the simplest models are more than adequate. When was the last time you had to use 1/4000 of a second?

Batteries

This was almost never an issue with film cameras (even with autofocus), but digital cameras are very power-hungry.

While in earlier models (except for the smallest compacts) AA-size batteries seemed to be the standard, there is now a trend towards proprietary power sources.

The common alkaline AAís do not last long in a digital camera; you can expect fifty frames or even less, but the NiMH (nickel-metal-hydride) rechargeable ones are better, and do not show much of a memory effect after many cycles. I am still using some of these, bought in Ď2000. As an extra benefit, the technology is progressing quite rapidly: while four years ago the charge of 1400 mAh was standard, 2300 mAh is not unusual today. And you can always resort to the alkalines in an emergency: they are available at any gas station.

The lithium-ion chemistry used in most of the proprietary batteries provides more charge per unit of weight and almost no charge loss in storage (which is a problem with NiMH).

More importantly, proprietary batteries also provide a greater profit margin for camera manufacturers, and this seems to be the decisive factor, with prices at $70 per unit being quite normal. While all Li-Ion batteries have the same voltage (which is the matter of chemistry used, and not of design), every maker sticks to a proprietary solution, clearly, to avoid competition. How else can I explain that the Nikon, Canon, and Olympus models have, in addition to the same voltage, the same shape, and differ only in contact placement, so they they cannot be used interchangeably? I can bet all three come from the same factory in Taiwan, branding them as needed.

Even if the NiMH batteries need to be topped off after they have not been used for a period of time, they are still my choice. One more reason: external flash units, even the dedicated ones, are still using AA batteries; when I travel with my Olympus C-5060 and the matching Olympus flash, I have to bring along two chargers ó a bit excessive.

Controls

Do you have an Olympus OM-1 or a Minolta XD-7 in your closet? Take it out and feel the controls: a pleasure. This is one of the few things you will have to give up with a digital camera, be it an SLR or a top-shelf optical finder model.

This is not just a matter of taste, but also of convenience, and speed of operation. With a very few exotic (and correspondingly priced) exceptions, the ergonomics of digital cameras seems to be driven by manufacturersí, not usersí convenience.

The most prominent feature on almost all models seems to be the big shiny button to press. Most other controls are presented as other buttons and wheels, with the feedback being provided by the LCD screen. Worse, many settings may require you to browse deep into the settings menu system ó not something you want to do when trying not to miss that critical shot.

Still, some cameras are worst in this aspect than others. While Iím not against using the menu system to set some options or special functions, Iím really unhappy having to use it just to change the exposure compensation ó something I need for almost every image. The same about enabling or disabling the built-in flash.

Before making your decision, have a look at the camera interface, try it out. Check if the features you use frequently are easily accessible. If not, look elsewhere.

Bells and whistles

There are many unessential features which can be added to a digital camera almost at no cost, often done entirely in software. They are not only cheap, they also may look good on paper, so why not? Here are some examples.

  • The "digital zoom". This is not a zoom, but an electronic process of cropping the central part of the image from the sensor, and re-interpolating it to the full pixel size. You can do that better in postprocessing on your computer, which has much more power and can handle more sophisticated algorithms. But then, it looks quite impressive in advertising: 12x zoom (3x optical, 4x digital). Believe me or not, people are buying it!
  • The "movie" feature. Many cameras, especially cheaper ones, can record short animated sequences at 15 frames per seconds (a few can do 30), with a very limited resolution. Iíve seen implementations with two modes, referred to as "standard" and "high quality", although "crappy" and "very crappy" would be more honest. The cheapest VCR you can buy second-hand will be two orders of magnitude better.
  • "Artistic" modes. These allow you to convert (in-camera, that is) the image to sepia or other tinted monochrome, or to negative. Any freeware computer program can do a better job in postprocessing, also allowing you to change your mind if you do not like the results.
  • Camera on/off effects. Most of us can live without the makerís logo and a sound chime every time the camera is turned on or off. I find this offending.

Some other features, while not essential, may be less irritating, sometimes useful, and for some users ó even essential. Again, a few examples.

  • Self-timer. Iím using it once a year, but your mileage may vary.
  • Remote control. Many cameras offer an infrared remote control interface. Strangely, while the corresponding remote unit is usually included in the box with models sold in the U.S., it has to be purchased separately in Europe. This seems to be a rule with Olympus, but not only.

    I find the infrared remote very useful in tabletop photography with a tripod, especially with models having no socket for a wired release (read: most non-SLR cameras).

  • Interval shooting. Very few models offer this option. While not essential for most users, it can be implemented entirely in the software, and some of us may need it ó certainly more than any of the "features" listed in the first half of this section.
  • Shutter sound effect. Seemingly just a gimmick, but I find this quite reassuring and useful under most circumstances.
  • Macro capability. Many non-SLR digital cameras, even in the compact category, offer surprisingly good macro capability, being able to fill a frame with an object less than three centimeters wide. Because the depth of field in these cameras, due to the tiny sensor size, is much greater than in film cameras with the same lens angle, macrophotography becomes easier and more enjoyable.

Instead of conclusion

This was a long article, but I can't help it. For this readership, composed of the people whose passion is photography, I canít get away with just anything. I feel I owe you more.

Still, I realize I was able only to scratch the surface on a number of issues. I would like to come back to some of those one day, therefore your feedback will be most appreciated.


This article was originally published in Quest, the quarterly newsletter of the Olympus Circle; September, 2004.

All camera pictures are from the respective manufacturers' promotional materials.

Back to my other Quest articles


Home: wrotniak.net | Search this site | Change font size

Photo Tidbits | The Gallery


Posted 2004/12/04 Copyright © 2004 by J. Andrzej Wrotniak