Off-brand 'ring' flashes, TTL? (by 2 users)

I've broken up my comments into two portions and imbedded them in the
original text.

Grover

: I have just purchased a Sunpak DX-12R, which is to my knowledge the
: only off-brand alternative to the Nikon SB-21 macro flash. Vivitar
: make a ring flash (model 5000?) and Sunpak has a DX-8R, but neither of
: these are TTL flashes.

Grant,

The DX-8R IS TTL and is a no-focussing light single circular flash tube unit

Grover Larkins

: Overall, I am satisfied that the DX-12R is preferable to the SB-21.
: Here are the advantages of each flash:

: DX-12R: - much cheaper (factor of two). I paid $218 + $30 (dedicated
: module) at B&H in NY
: - offers 1/2, 1/4, 1/8 and 1/16 (SB-21 has only 1/16) power
: ratios
: - has four, quite bright, focusing lights (SB-21 under
: batery power has only one, which is not much use)
: - did I mention it was much cheaper?
: - modular foot allows use on various brands of camera with
: full TTL (I'll probably never use this feature), and
: dedicated module can be shared among various flash heads
: (good if I ever buy another Sunpak dedicated flash)

: SB-21: - not actualy a ring flash. Has two independent linear
: flash-tubes which can be fired together or alone (this
: allows directional lighting and shadows when desired
: to expose surface detail, eg. coin photography)
: - offers separate under-exposure and over-exposure indicators
: - perhaps slightly more ruggedly built
: - has an optional flash difuser for short working distances
: (eg. reversed wide-angle lens)

: Nikon flashes have always been _quite_ pricey, and frequently not as
: fully featured as off-brand alternatives. In this case, the choice is
: not as clear-cut, but unless you _really_ need directional
: macro-lighting (and this can be achieved with the DX-12R by some
: homebrew masking of part of the ring-flash), I think the Sunpak is the
: better buy.

: I have two problems with the DX-12R. First, it only comes with
: mounting rings for 62mm and 67mm filter-sizes. This is _very_ anoying
: as I didn't discover the lack until I returned from my road-trip to
: NY. Of course I can use a step-up ring to mount the flash on my 52mm
: Micro-Nikkor 105/2.8, but I would prefer to have a non-kludgey mount.
: Sunpak do offer optional mounting rings in other sizes, but I have so
: far had no success obtaining one in Toronto (where the DX-12R sells
: for a ridiculous $CDN 838 list price, and is bought only by
: well-heeled dentists). The second problem is that the distance/f-stop
: scales for the flash's manual mode are calibrated for a 50mm lens.
: The flash manual tells me to see my lens manual for other focal
: lengths. Of course, my Nikon lens manual is mute on the subject of
: distance/f-stop calibration for Sunpak flashes.

: This brings up my questions. The manual is contradictory about the
: meaning of the distance scales. In one place it says the distance is
: to be read off of the lens scale, implying they are film-plane/subject
: distances. In another, it specificaly states they are flash/subject
: distances, and NOT camera/subject distances. Since the flash is on
: the end of the lens, I really don't know what they're trying to say.
: The second question is, how should I recalibrate the scales for my
: 105mm lens? I would presume for small magnifications that a 50mm and
: 105mm lens would require the same aperature to obtain a correct
: exposure, but that for higher magnifications the greater working
: distance of the longer lens might require slightly larger aperatures.
: Anyone care to comment on this? I will naturally be using TTL mode
: most of the time, but the ocasional macro-fill-flash at 1/8th power
: would be very nice, and I can't achieve that unless I know how to
: re-calibrate the scales for my 105mm lens.

: grant..

Comment on the Last here -- Use a flash meter and a steel rule to measure flash
to meter distance for the marked reproduction ratios on the micro-nikkor and
compile a table of f-numbers for each power setting on the flash unit at these
distances. I find a flash meter to be a practical necessity as the power ratio
settings can be off considerably -- heck the flash capacitors are usually
-20/+50% capacitance tolerance units and they change with age and amount of use
as does the tube's output

Grover Larkins