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B&W Film Processors
Q. I don't have a darkroom but want to try the Ilford IR-type film. I'd like to know if you can name a few reliable
film-processing companies that would develop the Ilford SFX 200 and put it on CD, whether I use 35mm format or a 120 roll.
Arlene Harper
via e-mail

A. You did not indicate where you live in the U.S.A., but I assume it's in the South since you have a BellSouth e-mail address. I checked with HARMAN technology Ltd., the firm that markets Ilford black and white products in this country, and they suggested this lab in the Southeast should be able to handle your Ilford SXF 200 processing: Dalmatian Black & White Custom Lab (7D Dundas Cir., Greensboro, NC 27407; (800) 603-8107; www.dalmatianlab.com). As always, I suggest you contact the lab first before sending any exposed film for processing and burning to CD. If you have any other questions about this Ilford product, you can contact Terry Bevens at HARMAN technology Ltd. (866-953-7821).

Right GN For Metz?
Q. I read with interest Jack Neubart's article in the February 2008 issue of Shutterbug concerning the test of the Canon Speedlite 580EX II and Metz Mecablitz 58 AF-1C shoe-mount flash units. The article lists the Metz GN as 192. B&H's Summer 2007 catalog on page 176 lists the GN as 138. Can you determine which GN is correct? I anticipate purchasing a new flash unit in the very near future as the Nikon SB-600 I currently use isn't hot enough for me.
Gene Sheridan
Owner, Sheridan Photography
Lee's Summit, MO

A. I checked the Metz website at www.bogenimaging.us, the firm that imports and services Metz products in the U.S.A. They show the GN for the Metz 58 AF-1 shoe-mount flash is 191 in feet. This should be the correct GN since they sell these flashes. It's quite high, so it should offer the extra light you need. I believe you will need the "N" version if you are using a Nikon digital camera.

Anatomy Of A Lens
Q. I'll attempt to be brief but that's hard for me. My questions are about the anatomy of a lens. I'm 74 years old and my first camera was a box camera I received at age 12. My first 35mm camera was an Argus C3 with telephoto lens that I purchased while in the Army in the early 1950s and my current camera is a Canon EOS 40D D-SLR with numerous Canon lenses. The point I'm attempting to make is that I'm not a novice when it comes to photography (however, that may be questionable). My questions concern SLR lenses. Most lens manufacturers list the specifications (e.g., lens construction [number of elements and groups]; angle of view; number of diaphragm blades; maximum and minimum aperture; minimum focusing distance; maximum magnification; and physical characteristics [diameter, length, weight, filter size, and type of zoom/focus adjustment]) with every lens they manufacture. I have a fairly good understanding of most of these specifications and most are useful. However, there are a few that I'm not sure as to why I need to know what they are or why the manufacturers find it necessary to tell me. Maybe if I understood their meaning I'd find them more useful. My questions are: 1) What is the importance of knowing the number of diaphragm blades in a lens and how does that number affect the quality of the lens? 2) What influence does the number of elements and groups have on the quality and effectiveness of a lens? When I look at most lens schematics I'm sometimes able to count the number of elements, sometimes not. Yet, I've never been able to locate the correct number of purported groups. I hope you have time in some future issue of your magazine to address these questions. I'm almost sure I'm not the only one interested in these questions.
L. Paul Dufilho
Thibodaux, LA

A. It took a bit of digging and research to obtain an accurate answer to your two questions, but online I gleaned the following, which, I believe is a reasonable explanation. Basically the number of blades used for a camera's diaphragm will have a direct relation to the final appearance of drastically
out-of-focus areas in the image. The greater the number of blades will result in a rounder and smoother shape. This also produces more gradually blurred soft focus areas. If you look at the spikes radiating from around small bright spots of light found on a nighttime cityscape photo you could determine the number of blades in the camera's diaphragm. With an odd number of blades there will be twice as many spikes as there are blades. The number of lens elements is dependent upon the angle of view and maximum speed of the lens. A fast wide angle lens has to have many elements to properly correct for optical aberrations. Conversely, a long focus telephoto lens having a comparatively small aperture (f/5.6 or less) typically has a simpler construction, often just a doublet construction consisting of two elements. A good normal focal length, non-zoom lens with a speed of f/2.8 or less typically has at least three or four elements. Today's wide range wide angle to telephoto zoom lenses often have 15 or more elements. Early zoom lenses often had bothersome internal reflections between the different types of glass, plastic, and air spacing which degraded both color saturation and contrast, primarily when pointed toward a bright light source. Today, optical coatings help minimize internal reflection of light thus zoom lenses now have both good contrast and color saturation. I trust that this helps answer your interesting questions.