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  The Reflector - Online
   

Feb. 2001



President's Message

Portrait of Steve Berkowitz

Photo FAQs

Photo FAQs

Eric Kissa
Below are some of the questions asked at the "Experts" session, answered now in more detail.


Q.: How good are independent flash units?

A.:Electronic flashes made by Canon and Nikon are so good that a lower price would be the main incentive for buying an independent brand flash unit for these cameras. Flash units made by Sunpak and Vivitar are less expensive but still very reliable and are often used by pros. Some models are dedicated to AF cameras and perform most of the dedicated flash functions. Some Sunpak electronic flashes have an AC adapter to save batteries during portrait or copy work. Very good flash units are made by Metz as well but they are more expensive.

A potential problem with using an independent brand flash unit is the risk of damaging the camera electronics. The synchronization voltage may be too high for some cameras, especially the Canons. As an example, the older Vivitar 283 flashes have damaged Canon EOS cameras, although the recent production Vivitar 283 flashes may be used. To test the synchronization voltage of an electronic flash, measure with a voltmeter the voltage across the contacts of the flash (The contact on the shoe is the negative). I measured the sync voltages of my Sunpak flashes with the following results: Model 221S 45 V, 433D 2 V, and 444D 2 V. The maximum allowable voltage, according to the information I have, is 6 V for Canon EOS, 25 V for Minolta Maxxum, 250 V for Nikon, and 600 V for Pentax cameras. I used Sunpak flashes on manual focus Nikons for many years without any problems.

A flash used as a slave is not directly connected to the electronic circuitry of the camera and a damage is not possible. Because dedicated functions are not needed, any flash unit may be used. However, the Nikon SU-4 slave sensor enables TTL flash control and requires a flash dedicated for Nikon.

Q.. Which handheld exposure meters are the best?

A. Handheld exposure meters are used for incident light, reflected light, spot and flash metering. For cameras with a spot metering option, only the incident metering is of interest. Actually, the incident reading is the most important exposure information because it measures the amount of light illuminating the object independently of the darkness of the object.

The Sekonic and the Gossen meters are the most popular. I have found that for incident metering the old Seconic analog L-398M easier to use than the digital reading meters such as the Digilite L-318B. The L-398M comes with a set of slides for each shutter speed/ISO combination and indicates directly the f stop. The average of the reflected reading (by the camera) and the incident reading of a handheld meter is very accurate. An incident light measurement can be obtained indirectly by reading a gray card with the meter in the camera. However, this procedure requires a camera with a 1/3 stop exposure readout. As a complication, handheld metering must be corrected for the filter on the lens. The real problem is a zoom with a variable f number. This is one of the reasons why pros prefer lenses with a constant f number.

Spot metering with the exposure meter in the camera is a convenient alternative to a handheld meter and, with some experience, quite accurate.

Q. Are teleconverters useful?

A.. Yes, if they match the lens, not only optically but physically as well (vignetting of the image or insufficient clearance between the rear element of the lens and the converter may be problems). Teleconverters, or extenders as they are usually called, degrade the optical performance of a lens (flare, loss of sharpness) but the loss is quite acceptable with a matching 1.4 x converter. 2x converters degrade the image quality considerably. Converters reduce the speed of the lens, one stop by the 1.4x converter and 2 stops by the 2x converter. This results in a slower AF response as well. However, I have found that the Nikon F100 or 90S can autofocus a 70-300 zoom extended from 300mm f/5.6 to 420mm f/8 reasonably fast in bright light. The Nikon AF extenders match only the new Nikon HMS lenses. The older AF lenses can be used with the Kenko PRO 300 ASF converter and presumably with the Tamron SP 1.4 AF PRO converter.

The converter should be attached first to the lens and the assembly then mounted onto the camera. The reverse procedure may confuse the camera electronics. Some camera makers (Nikon) recommend switching off the camera every time when changing lenses, with or without an converter.

Q. Point-and shoot (P/S) cameras.

A.. To concur with Lynn Maniscalco, P/S cameras have several advantages over single-reflex cameras (SLR). A small P/S fits into a shirt or trousers pocket and can be always with you. The little camera is ready to shoot as fast as it can be pulled out of the pocket. A small P/S is more mobile as a SLR, less intimidating and a great tool for candid photography. The smallest P/S, Olympus Epic (4.7 oz) is lighter and smaller than a wallet. The Epic is weatherproof and its clamshell design protects the lens very well. The 35mm f/2.8 lens produces sharp 8x10 prints and the camera costs less than $ 100.

P/S cameras have several limitations, of course. Of my small P/S cameras (Konica Mini A4, Yashica T4, Olympus Stylus Infinity and the Epic) only the T4 can deliver acceptably exposed slides. The fixed focal length (35 mm) is an asset for wide angle shooting but a limitation for general photography.

A P/S with a zoom lens is more versatile but the power zoom is slow to operate and the P/S zoom lenses are dim at the long focal length end. The zoom P/S camera is too large for a trousers pocket but a belt pouch is fine. The best of the P/S zooms, the Pentax 928 (28-90mm f/3.5-9) allows an ISO override and with a -0.5 compensation ISO 400 slides are properly exposed most of the time. Unfortunately, the camera is no longer made and nothing like it is available.

Send questions concerning photographic equipment (cameras, lenses, accessories, filters), photographic techniques (other than digital), and film, as well as information on international photographic exhibitions, to: ekissa @aol.com.


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