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Which strobe is the best for me ?


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#41 bobjarman

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Posted 19 April 2002 - 03:39 PM

Cool Ike! Does this mean mine and Sharpdivers are coming back to with the new and improved version?

#42 rstark

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Posted 19 April 2002 - 04:27 PM

Eric,
The books that he is refering to are probably written for Nikonos cameras that sync the flash only at 1/90th. With most modern SLR (or housed digitals) this does not apply because they sync through most if not all the range of available shutter speeds.

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#43 derway

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Posted 19 April 2002 - 04:33 PM

This discussion makes it clear to me, why I insist on using a ttl strobe control.

You guys are talking about tweaking the aperture to adjust for distance to subject, or to adjust for ambient lighting.

I say, either way is a limitation. I prefer to have as much latitude as possible, to use whatever fstop I want, to get what ever depth of field I want. That is almost always the actual image quality I want to effect.

Then, using aperture priority, the shutter speed sets the blue for me. As long as the ISO/fstop/ambient light is within the shutter speed range of the camera, the blue comes out.

And, using a good matrix TTL flash system, (say n90s or better), you get good flash exposure, as long as the aperture/ISO combo call for a flash within the least to most power, the strobe can put out.

I mean, 12 power levels isn't as good as the discrimination of a TTL controlled flash.

To me, when the camera can do TTL well, it leaves me free to think about focus, composure, and DOF, without having to fiddle anything else.
Don Erway
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nikon n90s/ikelite housing/twin SS-200 canon G2/ikelite/DS-50/optical TTL slave
sony V3/ikelite/DS-51/Heinrich DA2 slave

#44 herbko

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Posted 19 April 2002 - 05:05 PM

TTL has limitations. You need to understand what they are and have hardward that allows you to compensate.
Don't take my words for it. Read Cathy Church's comments under the "Sea & Sea YS90DX" section on her webpage

http://www.cathychur...m/latestdv.html

With a film camera like a Nikonos V or even a housed SLR, the common trick is to adjust the ISO setting on the camera.
If you only want half the light that the TTL strobe will deliver, double the ISO setting.
That of course is not an option with a digital camera. There is a flash EV adjustment on the Olympus which should work if I understand this correctly, but it's buried under a couple of menu trees and would take about a minute to get to. Not a practical solution.

That is the reason I opted for the manual controls of a YS90DX.

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#45 derway

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Posted 19 April 2002 - 05:27 PM

This is all a non issue these days.

All current digis have independent compensation, for ambient and flash exposure.

To say that the poor implementation of TTL in the nikonos, somehow makes it invalid, is something I hear all the time, and it obviously isn't true.

As I said, it is based on having a *good* implementation of ttl.
Don Erway
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#46 SharpDiver

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Posted 19 April 2002 - 07:00 PM

Okay, Ike, I will concede the 1/2 power = 1 stop, but will someone tell me why the math doesn't work backwards from the guide number?

Each shutter speed is half the light. Each f-stop is half the light. The logic is if the strobe is half the power it should be one stop, but if you work backwards from the guide number of the strobe, it would appear to be two. I await your learned explanation.

The "history" I referred to does not apply to the TTL slave sensor that you have produced successfully for years, but only to the digital version, of which the first batch I know of several that had to come back and be reworked. I am sorry if you think that is bullshit, but it did happen and some of your staunchest supporters here were victims.

As for Sea & Sea's angle of coverage claims, I must admit, I have never even looked at them. What I can tell you is that with a digital camera in a clear housing, if you use the fiber optic cable and read the directions that come with the strobe, it will fire in sync with the main flash of the camera and give you lovely color. Lots of people I know have done just that.

I will admit that to cover a wide angle lens, the YS-90DX is not likely to do an adequate job, but two of them work marvelously, for close to the same price as one DS-125.

#47 herbko

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Posted 19 April 2002 - 07:30 PM

Don,

Digital does not change the issue. and the ambient light exposure has little to do with it. TTL works by measuring how much light is reflected from your subject. Unless you can properly account for situations where your whole field reflects verse times where only a fraction of your field reflects and the rest of the light from the strobe just disappears into the blue water your TTL will give you the wrong exposure. People who shoot with housed SLR cameras still bracket their exposure and compensate for TTL errors.

Maybe Ike can jump in and correct me, but with his DS50 strobe, I don't think there is a way to bracket the exposure from the strobe except possibly by changing the flash EV compensation in the camera, which as I mentioned before is a pain to get to. I don't know if that has changed with the DS125.

Herb

[Edited on 4-20-2002 by herbko]
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#48 herbko

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Posted 19 April 2002 - 07:54 PM

Jeff,

The guide number is the distance at which the standard settings give you the right exposure. Light spreeds out in a sphere; you get only 1/4 the brightness if you double the distance.

Another way to say this is that if you half the distance to your subject, you will need to reduce the light by 2 stops to get the same exposure.

A strobe with a guide number that is 1/2 of another one is only 1/4 as bright.

Herb

[Edited on 4-20-2002 by herbko]
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#49 rstark

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Posted 19 April 2002 - 08:15 PM

If TTL was an option on my camera setup I would certainly use it SOMETIMES. TTL is not the solution for for every situation. The best examples of this are CFWA (close focus wide angle) and macro. CFWA shots are notoriously bad for TTL because your subject does not fill a majority of the frame and as a result your flash exposure sensor does not get enough reflected light back to squelch the strobe before it does a full dump. The result is a good background exposure but an over exposed foregroung. For CFWA the best way to shoot is manual. For macro nothing beats TTL. Although macro is very easy to setup for with manual settings.

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#50 ikelite

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Posted 19 April 2002 - 11:05 PM

We have a long history of product mistakes. No question about “several” slave sensors not working as Farris gloats, but a self serving analysis still leaves most of them are fine. One benefit of the fiasco will be an even better working sensor available in May.

The DS-125 is certainly a TTL strobe when hard wired unlike what Farris contends. No strobe can do TTL when hard wired to a Tetra housing. This is a housing deficiency.

Divide the guide number by two will be two stops, but this has nothing to do with strobe half power which is one f/stop by definition. Whew! Amazing how difficult it is to explain something so simple.

Ike

[Edited on 4-20-2002 by ike]

#51 SharpDiver

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Posted 20 April 2002 - 05:02 AM

Ike, I never gloated and I never contended in this thread or anywhere else that the DS-125 is not TTL.

What I did say is that it cannot work as a TTL hardwired strobe with certain cameras (Olympus and Canon come to mind) and certain housings.

Even Nikon cameras, where everything should be speaking the same language will have problems if the light sensor is hidden (as appears to be the case with the Aquatica 995 that has been discussed here).

#52 derway

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Posted 20 April 2002 - 05:15 PM

Hi Herb.

Well, on my G2, it is a back button, and I use compensation on the ttl quite frequently.

I find it fits the way I think, aperture for DOF, strobe comp for TTL exposure...

It has nothing to do with the strobes. Everything to do with the cameras.
Don Erway
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nikon n90s/ikelite housing/twin SS-200 canon G2/ikelite/DS-50/optical TTL slave
sony V3/ikelite/DS-51/Heinrich DA2 slave

#53 herbko

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Posted 20 April 2002 - 09:13 PM

Don,

Can't argue with that. Sounds like a good way to do it. Too bad it won't work for my setup.

Now. Should I spend $2k and get the G2 and housing or spend around $5k and get a D60 or D100....

Herb
Herb Ko http://herbko.net
Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#54 MikeO

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Posted 21 April 2002 - 04:49 AM

Wow,

What a thread! I will contribute one more thing: From the DS-125 manual on use of the strobe chart:

"Full Power Manual mode example for 100 ISO film speed: If you select f-8, the subject should be 4' away for proper exposure . . ."

"1/4 Power manual Mode example for 100 ISO film speed: The difference between each power setting is one full f-stop; therefore, moving from Full to 1/4 power decreases the light output by two full f-stops. If you select f-8, then reference two less f-stops (two numbers greater) than f-8 in the chart, which is f-16. Subject should be 2' away for proper exposure."

I may not understand all the formulae, but I have finally figured out how to read my manual :) .

Mike Oelrich

Mike Oelrich
Canon EOS 40D in Seatool housing, 100mm macro, Tokina 10-17, INON Z-240s.


#55 derway

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Posted 21 April 2002 - 10:08 AM

Herb, if Ikelite comes out with a housing for the d100, that combo should only run around $3k, plus ports if you don't have any...

Oh, plus lenses if you don't have any. Maybe that is where you came up with $5k...
Don Erway
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nikon n90s/ikelite housing/twin SS-200 canon G2/ikelite/DS-50/optical TTL slave
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#56 davephdv

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Posted 21 April 2002 - 08:07 PM

I have been diving for 3 days. Owners of an Ike 200, a pair of Nikonos 105's and a pair of S & S 90's all came up to drool over my D125s. Results show them to be the best on the boat. Secured 100$ with my shot of a wolf ell. They do exist south of Pt Conception (well, within site of Pt Conception though I have seen them at San Muguel Isd.)

Note, if Ike had his act together I would have been taking this images with my CP 5000. (i. e. where is my housing?)
Dave Burroughs, Nikon D300, D2X, Subal housing, DS160 strobes

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#57 lanierb

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Posted 22 April 2002 - 09:23 AM

Maybe I can help clear up the confusion on the guide number math. As Ike says, 1/2 power is always one stop by definition. 1/2 power gives 1/2 the light, which is 1 stop. The error some were making was in the guide number math. The formula f=guide number/distance is correct. However, 1/2 power does NOT cut the guide number by 1/2. 1/2 power cuts the guide number by a factor of 1/sqrt(2), or exactly one stop. 1/4 power cuts the guide number by 1/2=(1/sqrt(2))^2, or two stops.

Message for Ike: I loved the DS-125 when I checked it out but, due mostly to the lack of control/poor TTL provided by digital cameras/housings, I felt that I *needed* to have finer manual control, so I bought two YS-90DX's and have been happy with them. If the DS-125 had finer manual control, I think we would all agree (well, maybe that's asking too much!) that it would be the flash of choice.

#58 SharpDiver

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Posted 22 April 2002 - 02:21 PM

for explaining the relationship between guide number and half power without abrasive comments and personal attacks.

I have edited all of the messages in this thread that involved the errant calculation.

Another issue of discrepancy in this thread is how much effect the 12 settings on the YS-90DX have. I did not quote the Sea and Sea manual (as rstark did) because an engineer from a competitive manufacturer told me it was impossible for the YS-90DX to have 7 stops of adjustment.

Both debates led away from the crux of the matter, which is if you are shooting manual, more control is better.

On another point...

Ike said...
The DS-125 is certainly a TTL strobe when hard wired unlike what Farris contends. No strobe can do TTL when hard wired to a Tetra housing. This is a housing deficiency.


Ike, if you're going to nail me to the wall for a mistake, you should expect it in return. This is not a deficiency in the housing. A hard-wired port in your housing would be no more successful at TTL with an Olympus camera than the Tetra. The camera doesn't speak "Nikon" and most strobes do. You can argue that your digital slave sensor provides TTL, and it can in transparent housings, but at that point the discussion was hardwired connections. As for TTL performance of your strobe, I did not anywhere in this thread say that your strobe is not TTL. I did say, and camera buyers should note, that TTL hardwired function is very dependent on camera brand and sensor placement. For digital hardwired TTL to work (on either Ikelite or Sea & Sea strobes) the camera has to be a Nikon and the sensor has to be in the open.

#59 lanierb

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Posted 22 April 2002 - 04:30 PM

I can't figure out how to quote previous messages, but in response to the discrepancies above about the YS-90DX's 12 power settings, I ran a test. I happen to have a very accurate flash meter for land photography that I used to measure the power output of the 12 settings for one of my YS-90DX's. (For those who are interested, the setup was YS-90DX on a tripod with fiber optic sensor hooked to a vivitar 283 flash which was in a dark bag, in a dark room. The 283 flash cord was hooked to the flash meter, which I operated manually in spot mode aimed at the same point across trials and held at approximately the same point. I popped 3-4 flashes per setting to be sure I had it right.)

Here are my results stated as stops relative to a full power burst. I think that they are accurate to 0.1 stops (they were *very* repeatable).

Full: 0.0
--: -0.5
-1: -0.8
--: -1.4
-2: -2.0
--: -2.3
-3: -3.1
--: -3.4
-4: -4.2
-5: -5.5
-6: -6.5
-7: couldn't measure

I couldn't measure the -7 setting because I have a short tie-wrap attached to the flash dial that makes it easy to set it with thick wetsuit gloves on (it's cold out here) but that makes it impossible for me to set the flash at -7. I didn't think it was worth removing the tie-wrap to measure a setting that I never use.

The bottom line is that there is some inaccuracy in the power settings, but they are basically as advertised. The lower settings are if anything lower than advertised. Other than that, on my flash the biggest variance was the -1 setting, which is supposed to be -1 but was actually -0.8. The "1/2" marking, which is near the -2 setting on my flash, seems to be completely wrong. BTW there could be variance across units so don't interpret these numbers as necessarily right for your flash.

#60 derway

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Posted 22 April 2002 - 04:51 PM

Lanier, do you find that you use the settings below -3 or so, underwater?

Thanks for doing the experiment!
Don Erway
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