The question has been asked MANY times, "Why do we only get to use a 50mm lens"? Well for several reasons. First, the short answer. 1. The 50mm lens is a GREAT learning lens. 2. It is inexpensive and fast. 3. It is a good lens (not all lenses are created equal).


A graphic from a famous musician comes to mind:



Do you know who gave us such an awesome graphic showing how a prism bends light?


The fact is, light bends when it goes through ANY glass...not just a prism. How little it bends is the question of good of an image it will produce.


Now, the long answers.


1. The 50mm lens is a great learning lens. MOST introductory schools start student photographers on a 50mm lens to help reinforce the basics with a single focal length . Control perspective by controlling the subject to camera distance...IOW, move your body...zoom with your feet.


2. Not only is a 50mm lens one of the least expensive lenses to purchase (or replace in the case of loss), it is also one of the fastest in terms of it's light gathering capability. The Pentax 50mm is generally a f/2 lens. The FASTEST zoom we have is a 28-85/3.5-45 (effectively f/4 at 50mm), which means that it lets in HALF the light than the 50mm f2 lens does when wide open. Another part of this challenge is that the longer the focal length, the faster the shutter required to STOP the camera shake from blurring your image.


3. You have heard the saying, "You get what you pay for". Well, nothing is more true than with lenses. There is a reason why some 70-300 zoom lenses are $150 and some 70-200 are $1500. The fact is that light bends when it goes through glass creating what is called distortion, such as CA (Chromatic Aberration). Lens manufactures know this...and design the special glass so as to limit the bending...and/or apply special coatings to correct for the distortions and reflections.  Zoom lenses are even more complicated because of the number of pieces of glass that a lens contains. A zoom lens contains numerous elements of glass in numerous groups. It is not uncommon to have a zoom lens with 14 elements in 12 groups (see some samples here). This cause significant distortion (barrel and pincushion) as you zoom from one end of the focal length to the other. In addition, the CA becomes quite significant. One lens I own has 21 elements in 15 groups. Fortunately, 5 of those elements are ED Elements...that is, they are coated with special coatings for extra lower dispersion of the light. Of course, to get these 5 ED coatings, you have pay $1,650.



Conclusion: This is not to say to not shoot with a zoom...but you should be shooting in the best of light. 1. They require more light because of the smaller apertures. 2. Need faster shutter speeds at longer focal lengths...at just the time when they offer less. 3. Perform poorly when shooting in poor light...ie. hazy, or light coming into the lens. In fact, zoom lenses perform even MORE poorly when wide open or closed down. A great deal of effort is spent by MANY people determine just how good is a lens. Check out this page (scroll down to graphic) to see how good a $1,200 Nikon lens fares when shot wide open at wide angle...and that is for $1,200.


Comparison of Lens Focal Lengths:




So, having now said all of that. Here are the zoom and extra lenses that are available for check out:


Lens		Aperture	Filter	Other
18-55 af	3.5-5.6		
18-55 af	3.5-5.6		
18-55 af	3.5-5.6		
Text Box:    
Zoom Lenses are available for ZX-m or similar cameras and             above.             
AF lenses are for DSLR checkouts only.
50-200 af	4-5.6		52	
35-80 af	4-5.6		49	
35-80 af	4-5.6		49	
100-300 af			55	

35-75		3.5-4.8		55	macro
28-80		3.5-4.5		58	macro
28-80		3.5-4.5		58	macro
28-80		3.5-4.5		58	macro
35-70		2.8-3.8		55	macro
28-105		3.5-4.5		72	macro
70-210		4-5.6		52	macro
35-80		4-5.6		49	
35-80		4-5.6		49	
80-200		4		55	macro
80-200		4.5			macro

135		3.5		49	
100		2.8		49	
135		2.8		55	
135		2.8		55	
135		2.8		55	
135		2.8		55	
135		2.8		52
2x		Teleconverter - need plenty of light as you will loose 2 stops of light.



Now, to something REALLY complicated...Digital vs. Film Focal Lengths


Unfortunately, there is a little bit of confusing terminology out there. There are THREE focal MAIN lengths. ALL of them try to compare what you would see with a 35mm.
35mm - the stated focal length is what you get. A 28mm lens is 28mm.
Digital SLR APS-c sized Imagers - a multiplier of the actual focal length times the crop created by a sensor that is different from the size of a standard 35mm camera. The multiplier varies from camera to camera even with in one manufacturer. For example, all of Nikons Digital bodies require the lenses focal length to multiplied 1.5. So, if I have a 10-20mm lens (like I do) then I REALLY only have a 15-30 35mm film equivalent...which is still pretty darn wide. Unfortunately, that 10-20 doesn't even work on a film camera, so it is a moot point...except that it is only a 10-20 on a digital camera. But on a Canon, the multiple is sometimes a 1.6...sometimes a 1.3, sometimes a 1.8.
Digital Pocket Sized Camera Imagers - really small chips that have a completely different meaning for every different camera because the designs are so different. IOW, you really can't compare one Compact P&S camera's zoom lens to another, unless they BOTH reference the effective 35mm equivalent. IOW, two cameras may both have  6.3...but you have to look at THAT cameras own literature to determine because depending on the size of the chip, which can be half or quarter the size of the APS postages sized chips, and then how far away the lens is from the chip.