DCRP Special Report: SR Electronics Ring Flash Review
by Tom Beardmore (December 17,1998)

Okay, I'll admit it. I'm a detail-oriented kind of guy. I'm fascinated by the minuscule details that come to light through macrophotography, in even the most ordinary subject matter. As a case in point, just take a look at the details that you can see in this outdoor faucet timer by clicking on it.

All you need is a digital camera that either has a built-in macro mode, or one that supports a close-up lens set. If the camera permits you to preview the image directly through the lens as well (such as TTL cameras like the Olympus D-500L, D-600L, or D-620L) or by using its built-in LCD (like the Nikon CoolPix 900s and others), you've got all the basics. As long as you're working with plenty of available light, you can produce some great detailed close-ups.

Indoors, however, it becomes much more difficult (if not impossible) to get satisfactory results with most digital cameras available today using their built-in flash units. Overexposure, harsh shadows, uneven illumination, and glare all contribute to less than satisfactory results. In conventional film-based photography, the answer is to use a ring flash unit with a single lens reflex camera. A ring flash is an electronic flash unit in the shape of a ring that attaches to the front of the lens using its threaded filter mount, surrounding the lens to produce soft, even illumination of the close-up subject.

Unfortunately, the current crop of consumer digital cameras poses some obstacles to using a ring flash. Most popular digicams have no threaded filter mounts like 35 mm cameras do, so there's no place to mount a ring flash on them. Among those few digicams that do have threaded filter mounts, some of the more popular models have no external flash synch socket, notably the Olympus D-500L & D-600L (although the new D-620L has one). Without an external flash synch socket, there is no way to synch the ring flash with the camera's shutter.

Although the photographer could use a slave trigger to set off the flash ring (a slave trigger is designed to set off a secondary electronic flash unit when it detects the flash of a primary unit), conventional slave triggers fire as soon as any flash is detected. Several popular digital cameras flash twice when taking a picture: the first flash sets the exposure and white balance, but it's the second flash that is used to take the picture.


The Solution: SR Electronics RF-50
Let me introduce you to the RF-50 Ring Flash from SR Electronics. Like ring flash units made for 35 mm SLRs, this unit attaches to the front of the digital camera's threaded filter mount. Unlike conventional ring flash units, however, the RF-50 is a slave ring flash that has been designed to trigger on the second flash of the digicam, so it doesn't require a direct connection to the camera's flash circuitry. By using this unique approach, the RF-50 succeeds in solving all of the previously-mentioned obstacles. It is designed to work with digital cameras that have an equivalent ISO number of 100, and is especially well-suited for use with the Olympus D-500L, D-600L, and the new D-620L. If your digital camera has an ISO equivalence rating other than 100, or it doesn't have a threaded lens filter, you probably won't be able to use the RF-50 with it. The remainder of this review assumes you are using one of the previously-mentioned Olympus digital cameras.

The RF-50 includes 49 mm, 52 mm and 55 mm series VII adapter rings, and a 43 mm to 49 mm step-up ring. To mount the RF-50 onto the Olympus, screw the 43 mm to 49 mm step-up ring into the threaded filter mount of the camera. Next, select the 49 mm series VII adapter ring and screw it onto the back of the RF-50. Finally, mate the RF-50 to the step-up ring on the front of the camera and screw the two together.

The RF-50 incorporates a built-in automatic exposure sensor that is effective from 1 to 3.1 feet (30 to 95 cm), so you'll find that most of your close-up photos will be perfectly exposed as long as you don't get too close to the subject; remember that the sensor is not designed to control the exposure closer than 12 inches to the subject. You can also override the sensor by switching the ring flash to the manual mode, but you'll be on your own if you do.

In order for the automatic sensor to accurately perform its function, you'll have to mount the RF-50 in a manner that blocks the camera's built-in flash unit (or find a means to otherwise reduce its intensity). Fortunately, because RF-50 has a free-rotating Series VII screw ring on the back of the unit, you can orient the ring flash in any position needed. I found that it was possible to mount it upside down on my D-600L, as shown here, so that the bulk of the unit's body was positioned directly in front of the camera's built-in flash. This is the way I used the unit in all of the example photographs that follow,


The Proof: Comparative Examples
I suppose the best way to demonstrate what the RF-50 can do for you is to show you a few examples. In all examples which follow, the picture on the left was taken with the camera's built-in flash, and the picture on the right is taken with the ring flash. To see an enlarged view of the photo, click on the images. The results speak for themselves... 


Cellphone with Normal Flash Cellphone with RF-50 Ring Flash

In the pictures of the cellphone, note that the keypad's slightly curved surface produced uneven illumination using the built-in flash. In the same picture taken with the ring flash, the lighting is more even, and there is no "hot" side.


Thumbtacks with Normal Flash Thumbtacks with RF-50 Ring Flash

In the pictures of the thumbtacks, the example taken with the ring flash produced a less harsh image and showed better color saturation. Shadows were less apparent, and there was much less glare in the picture taken with the ring flash.


Bike with Normal Flash Bike with RF-50 Ring Flash

In the picture of the miniature bicycle wheel taken with the built-in flash, the shadows made it difficult to tell where the black rubber tire ended, and the shadows began. There is also a very bright reflection coming from the crank. None of these problems were apparent in the photo taken with the RF-50.


SmartMedia with Normal Flash SmartMedia with RF-50 Ring Flash

In the final example, I intentionally created a difficult lighting situation by photographing a dark subject on a dark background. The differences here were rather subtle, such as the washed-out label of the standing SmartMedia in the photo on the left. The photo on the right had better overall color saturation.

I think you'll agree that the RF-50 consistently produced better results when photographing close-up subjects than when the camera's built-in flash unit was used!


Getting Your Best Results
For best results, SR Electronics recommends the following tips when using the RF-50 with your camera:

  1. Zoom the camera's lens in as far as it will go (i.e., maximum telephoto) before taking the picture in order to eliminate unintentional vignetting.
  2. Always hold down the 1.2 ft. quick focus button on the camera when focusing the camera and when taking the picture. This locks the focus (a problem sometimes observed when using Olympus ZLR cameras under low-light conditions) and sets the proper exposure.
  3. Always use the Automatic mode.
  4. Remember to use the Macro mode on the camera; on the Olympus, just press the "Macro" button.
  5. Block the camera's flash by rotating the ring flash as shown earlier, or reduce the built-in flash's intensity by partially covering it with black tape.
  6. To further reduce the flash's intensity, use a circular polarizer or a neutral density filter on the camera's lens.

Having used the ring flash unit, I've developed a few tips of my own:

  1. Use of a +1, +2, or +4 close-up lens set will help you get as closer to your subject but...
  2. Getting too close (i.e., closer than 12") can fool the RF-50's automatic sensor. To compensate, place a Kodak 50% gray card just out of the field of view of the camera's lens, but immediately in front of the ring flash's automatic sensor. Minor exposure corrections can be made using the +3/-3 automatic exposure control of the Olympus.


Almost Perfect
As much as I liked the RF-50, there were a couple of minor inconsistencies I found while using the unit. For example, the owner's manual states that the unit will automatically turn itself off after a period of time. Unfortunately, it doesn't shut itself off automatically, no matter now long you wait, and there's no "off" button. To turn it off, the only obvious solution is to open the battery compartment and remove the two "AA" batteries. However, I discovered an undocumented feature: if you wait for five minutes after the red "Ready" light begins flashing, holding down the green "Power On" button for two seconds (and then releasing it) will turn off the unit. The "Ready" light will continue to flash for a few minutes, but the battery will no longer be constantly charging the flash unit. [NOTE: if you press the "Ready" light, which is also the "Test" button, the RF-50 unit will flash and immediately turn itself back on.]

I also found it puzzling that the unit didn't include the flash synch cable, even though the manual indicates that one is supposed to be provided with the unit. I realize, of course, that the RF-50 is designed as a slave unit, and that it is triggered by the Olympus' own built-in flash. However, with the introduction of the D-620L, which has an external flash synch socket, and other digital cameras which have them, I think it would make sense to include the flash synch cable anyway.


So Who Would Use This?
Anyone who has a need (or a preference) to photograph close-up subjects should give serious consideration to SR Electronics' RF-50. Although it has a couple of relatively minor shortcomings, it's the best solution (if not the only solution) presently available for digital photographers, and especially for users of the Olympus D-500L, D-600L, or D-620L cameras. Some may think that its $250 price tag is a bit steep, but if the price of the RF-50 is compared to conventional ring flash units, you'll find that it's priced competitively.


Thanks to Larry Wilson at SR Electronics for allowing me to review the RF-50. SR Electronics offers several different kinds of electronic flash units for digital cameras, and a really cool slave trigger that converts conventional electronic flash units for use with digital cameras. If you're interested in more information about the RF-50 or any other slave units they offer for digital photography, SR Electronics can be reached at 800-234-7745 or visit their website by clicking here.

As always, if you should have any questions about this review, feel free to drop me a line!



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