Photo Technical

Lenses, millimeters and pixels – oh my! – A02

Many of you may have been left wondering from my discussion of lenses in the previous article, what is meant when digital camera advertising describes the lens to be “35mm equivalent” to a zoom range, such as 38mm to 114mm.  An brief explanation will provide me a good side way into an important factor of digital camera quality.

The 35mm format has been with us a long time.  We all recognize 35mm camera to be one that used 35mm film, which provided negatives of 24mm x 36mm in size.  The size of the film, along with the speed of the film, i.e. 100, 200, 400 ISO, etc., had much to do with the quality of the prints that were possible.  We also knew that a 35mm camera with a 28mm lens (or less) would give us wide angle scene capability; a 50mm lens would be a normal equivalent to our eyes,  and a 100mm or longer would enter us into the narrow telephoto lenses that bring distant subjects closer.  Lenses were designed for this specific format.  Advertising for the new consumer digital camera is (still) based on this equivalent familiarity.

The important aspect to keep in mind, worth repeating from my last article, is that a 35mm or 38mm lens unfortunately is not very wide angle and therefore less useful for tight quarters or expansive panorama photographs.  There are a few “point and shoot” cameras offering a wider angle of view of 28mm.  If this feature is as important to you as it is for me, look for it.  The only other option is to buy a digital SLR camera allowing interchangeable lenses, and then if willing to pay an expensive price tag you can go even wider.

It is much easier in the digital world to go telephoto than it is to go wide angle.  This is due to the size of the capturing device, what has replaced film, and goes by either the acronym CCD or CMOS chip.  With only several exceptions all of the digital cameras, “point and shoot” as well as SLR’s, have chips smaller in size than a film negative.  The reason is, smaller chips are less expensive to manufacture.  The only advantages to you is the affordable pricing and greater telephoto capability.

I could go into the latter lens capability, but I am going to ask you to take my word for it.  Discussing the details on this enters into a more involved explanation of optics, but if it interests you let me know.  Talking about chip size will be more helpful.  This is related to resolution and the quality of the prints you can expect.

The chip size has a direct relationship to the resolution, whether it is 2 or 8 megapixels (with a few SLR digitals offering more pixels).  Another way you see this size described is maximum 1600X1200 or 3500X2300 pixels.  If you divide those numbers by 300 (the dpi – dots per inch for quality prints) you will get what print size is optimum for the cameras resolution, that is approximately 5X4 or 12X8 prints, respectively.  It is easily apparent why more megapixels are more desirable.

But, simply more megapixels on a chip is not the only factor in the final quality of a print.  The size of the pixel is equally important.  Completely opposite of film where the smaller the grain the sharper the photographic print, larger pixels generate less noise and better results.  Therefore, if you make a chip the same size as a negative, that’s even better.  Yet these two factors are just pieces of the puzzle in getting good photographic results.  The quality of the lens (and size again is in the equation) makes an important difference.  Of course, more pixels, larger pixels, better lenses translate into higher prices.

rom the start I could simply have told you buy a camera with more pixels and a better lens, or better still go buy a more expensive digital camera.  Instead, in the simplest way I can, I’ve provided information that will either give you better insight on the digital camera you own, or help you with new camera purchase to best suit your needs.  This is only the very tip of the iceberg, so to speak.  .   That’s it for now: Permission to come ashore.  Send me your questions to possibly cover in next issue.