Delta Macro ring

[Javelin]

I picked up one of these and have had the chance to give it a run. The flash tube is one of the round types instead of short straight rods.

For medium distance it lit a small room with very pleasing even light but I really wanted macro shots.

This was 1/125 F25 ISO 400 100mm The subject is a new snail and is maybe 10mm long. that is a dandelion leaf he is on.


1/30 F25 ISO 400 100mm


You can see the reflection of the ring in his antennae on that one.

These flowers are only about 2mm across.


The above were shot with 100mm but there was also a DCR 250 diopter attachment for some shots (the flower)

The build quality is quite good for the Price of the unit. it fits well and feels solid enough. the ring unit is made to rotate. So far I have about 250 shots on a set of batteries. the unit will only work in TTL mode there is no other buttons one it other than a shoe release and a test button. the unit powers on with a slide switch which is kinda cheap but it's a simple slide type. the flash shoe fits the top of the A700 properly and doesn't;t wobble any more than my other flashguns. The ring built onto the flash fits 52mm and there is a nice selection of adapters that comes with it. the only one missing was a 49mm which I picked up and fits the DCR250 and the MMinolta MD 50mm I use on my bellows (haven't tried the bellows yet)

the flash responds well to compensation but does tent to underexpose a little, at first I thought it was weak but it's plenty powerful enough to light through F32 with enough to spare (you can over expose at 1:1+ at F32)

the only bad point is .. well there are 2 the preflash pulses are very slow. easily distinguishable and will cause lazy eye. The other draw back is in the specs for the flash. and I never saw this posted in the ads is that that flash duration is only 1/700. thats a long time when the Minolta Ring flash is 1/50 000 or faster. there aren't many other bugs around yet (faster ones) so I don't know how this is going to affect those images but overall I'm pretty pleased with it as is.

[David Kilpatrick]

The maximum flash duration will be 1/700th - full power. I know for sure the Delta does not use a fixed duration power variation - that is VERY expensive to make - but shortens the flash pulse like any other gun, to achieve short durations. The Minolta flash 1/50,000th is its minimum duration, I think. It's harder to make a true ring flash with very short durations as the circular tube is physically longer, and this helps determine the flash pulse and t=0.5 time.

Also, Minolta quote durations which may not be T=0.5.

To explain to newbies, flash duration is never expressed for the total length of the flash burst, which is T=1. That means T (time) to delivery the full (1) output of the flash. Flash has a peak followed by a declining burn which contributes to the exposure and also warms up colour temperature. T=0.5 is the industry standard: 'the time taken for the flash to deliver 50% of its overall light output', which normally means about 1/5th of the total T=1 duration, because of the sharp sudden peak and the gentle slope 'tail'.

So, a flash with T=0.5 1/700th may well have a T=1 duration of 1/125th. Generally, battery operated small guns have a sharper peak and shorter tail than studio flash. T=1 for a camera top gun might be 1/350th instead. But ringflash units use studio flash type tubes. The Minolta macro flash does not, it uses short tubes like the camera-top built in flash.

Some makers have quoted T=0.1 or T=0.2 as their 'duration' in the past because they measured only the initial peak, and ignored a long tail of light emitted after this. This was very deceptive and it's not common now.

David

[Greg Beetham]

I've always sortof wondered about how much influence the tail has after the pulse, being dimmer by factor x (and diminishing) than the actual f-stop balanced exposure pulse. What I mean is, will the tail register enough too show any movement by the subject after the initial pulse?
Another thing that could/should influence how the flash behaves is how close to maximum output (or not) of the unit the situation demands, ie. the combination of settings and circumstances...how big is the distance, (near maximum, medium, or close), what f-stop is being used, and what ISO is set. If say, the distance is reasonably close, the f-stop is not deep and the ISO is high, the pulse that the unit would deliver should be of much shorter duration (I would reasonably expect...) than where the distance is close to maximum, the f-stop is deep and the ISO is not high.
That's where I always thought some manufacturers got those incredible 1/30000-1/50000sec. figures from, taking the results from the most advantagous combination of settings etc. I'm not sure if there is any way of verifying them either.
Greg

[Javelin]

Walt may be able to shed more light ( heh ) on the limitation of the 1/700. I think it has to do with the quality of capacitors, their potential (max charge) and how quickly they can discharge. The minolta is a lot more powerfull.. seeming... if that makes any sense. although even the minolta had trouble lighting large areas it seems very quick in opeation, the round tube might have something to do with the time too. Also this flash can light things almost inside the ring area. the tube is shaded on the outside and reflected forward but the inside is all clear plastic difuser.

One trick I started using was using the flash on the DCR250 wich also gives it a quick disconect from the lens so while my subject is getting his portraits done I can pop the thing off and get a diferent kind of shot in an instant.

[Greg Beetham]

I guess you could see if the 1/700sec duration is as claimed for all exposures or does vary according to circumstances. On the A700 you can set whatever ISO you want in M mode (you can't on the A100, it's locked in ISO100), TTL should still work OK in M mode, so what you could do is find some fairly average ambient light like 1/5sec f4.5 ISO200 then take a photo at about 15" with the ring flash but reset the ISO to 1600 or 3200 and the shutter to 1/1000sec (f4.5)...the flash is burning longer than the shutter at 1/700sec so you shouldn't end up with a dark band accross the bottom of the photo..(in theory), although I think there will be one of some sort, whether it's a really black one or a faint one remains to be seen.
If it's a black band then the flash has cycled at much higher than 1/700 sec, if there is a visible smudge then it probably is cycling it 1/700sec....at a guess.
You might have to play with the f-stop if too much ambient gets back into the mix, try f5.6 or f7 etc.
Greg

ps. The whole thing probably won't work anyway, the flash ready signal will most likely re-set the shutter back to 1/250sec...even in M mode...and there is probably no provision for M mode on the flash itself....coises foiled again..

[Javelin]

yup that won't work I could use a trigger cable though. I think I have one here (sync cable with a hotshoe on it) and just photographe the ring at diferent speeds unti I see the shutter leaf

[Greg Beetham]

Nah, I don't think that one will work either, it's probaby mean a full dump regardless (not TTL regulated), and therefore always at the 1/700sec quoted speed...hmmm gotta tink about dis.
Greg

ps. It's just another example of what I've been saying about M mode all along, it's a gammin one....not a real one.

[Javelin]

well if we want to see what the max speed is it should be at full power no?

[Dusty]

I guess you could see if the 1/700sec duration is as claimed for all exposures or does vary according to circumstances. On the A700 you can set whatever ISO you want in M mode (you can't on the A100, it's locked in ISO100), TTL should still work OK in M mode, so what you could do is find some fairly average ambient light like 1/5sec f4.5 ISO200 then take a photo at about 15" with the ring flash but reset the ISO to 1600 or 3200 and the shutter to 1/1000sec (f4.5)...the flash is burning longer than the shutter at 1/700sec so you shouldn't end up with a dark band accross the bottom of the photo..(in theory), although I think there will be one of some sort, whether it's a really black one or a faint one remains to be seen.
If it's a black band then the flash has cycled at much higher than 1/700 sec, if there is a visible smudge then it probably is cycling it 1/700sec....at a guess.
You might have to play with the f-stop if too much ambient gets back into the mix, try f5.6 or f7 etc.
Greg

This won't work because the flash fires when the first curtain/shutter blade reaches fully open. (x-sync) At 1/1000 sec the rear curtain will already be closing before the first reaches full open. You just have a traveling slit.

The old flashbulbs worked because fb-sync started the flash firing before the shutter even opened. The long flash duration illuminated the scene long enough for fairly even lighting. If you used too fast of a shutter speed with a flashbulb, you usually got a bit less light (burning hadn't reached it's peak yet) but usually still got usable negs.

Dusty

[Javelin]

so if sync is 1/200. at 1/700 the seccond curtain will be 1/2way across the frame or so. this should be easy to calulate .. at least enough to see if 1/700 is real and it's not really 1/400 right? sorry I haven't put my mind to this yet it's bee a couple days of distractions

[Greg Beetham]

Yes I was forgetting you'd have to base the test on the cycle time of the shutter and as far as I know the fastest possible cycle time of an A700 shutter is 1/250sec regardless of what slit it's using or not.
So 1/700sec is too fast to test with a shutter that can only physically move at about a 1/3rd of the speed.
I can't think of a test to verify the 1/700sec speed is the slowest speed it has (related to maximum output), and can get a lot faster if necessary, like the sensor flashes can.
Greg

[Greg Beetham]

Maybe if someone still had a funcional darkroom (one that is actually dark, mine no longer is at the moment), and an IR trigger that can set the flash off while the shutter is fully open. Then all you would need to do is drop an object past the front of the lens at a preset macro-ish focus distance (with a backboard) through the trigger beam and vary the ISO from low to high in a series of shots...the subject should get visibly sharper at higher ISO's...although 1/700sec might already be fast enough to stop 33ft sec/sec acceleration....hmm might have to drop the object/subject from up near the ceiling to get maximum speed.
Greg

[Javelin]

when will the sync port fire the flash? when the first leaf hits the top of the frame? surely not if the shutter speed is set to 1/700. if it is set to 1/700 and the flash pulse is 1/700 then wonl't there be only one lit bar in the middle of the frame representing the slit?
on the other hand the1/700 is probably the peak, there will be light fall off as the residual charge is used up so it may somewhat light the remaining part of the frame.

I think I can test this in a pretty elaborate way.with a spinning disk target with radiating graduations .. in a photo all will be solid circles except the ones that are less than 1/700 s between marks. you'll see the spaces between... some diferent kinds of print mght make a guage for flash pulse duration measuring dunno if I have the energy for this at the moment.

[Greg Beetham]

Nah, I wasn't saying set the shutter at 1/700sec, the shutter was/is set open for the duration of the falling object (marble, sinker, ball bearing, whatever) using a remote control, and being in a fully dark room the only exposure that's recorded is when the flash goes off. After the flash goes off one can then close the shutter with the remote.

But your idea of a spinning something or other is an excellent one, what about a fan, the rpm on a fan motor should be available, from that the linear speed of the fan blades could be worked out (a variable speed one even better), then all you would have to do is vary the amount of ambient light from fairly bright to almost total darkness and the f-stop, ISO etc...
Greg

[Greg Beetham]

Thinking about it a little more, it'd be fairly easy to compare a couple of shots I think, one in bright light without flash, and fan at full speed, and the shutter set at 1/640sec or 1/800sec S mode (I can't set my A700 to exactly 1/700sec) but 1/800sec would probably be good enough hopefully, and then do a shot inside in poor light at high ISO (A or M mode) with a fairly open f-stop and see if the flash is better at stopping the fan blades or the high speed shutter is, if the flash stops the blades cold then we know it can auto quench up to high speeds.
Greg