TTL Test

Hi Guys,

I was hoping that someone would chime in and let me know how to conduct a TTL test.

I have an S&S Mk I converter and S&S YS 120 strobes with a Nikon D70S camera.

So guys, how do I do it? Is it a series of images with different FStop settings or something else?

When I take a picture, the little green light on the TTL converter stays green. Does this mean

a correct exposure? As you can see, I am a little confused, so any help would be great...

Thanks for taking the time,

Bruce...

The best way would be to set up the camera on a tripod or similar and aim it at a static subject. Take a number of shots at different f/stops. Overall exposure should be the same if TTL is working (unless you choose too large an f/stop - too small an aperture - to properly expose the image. If you had a gray card it would be even better.

A simple TTL test is:

-set shutter at the sync speed of your strobe (usually, around 1/250 second)

Part A "quench test"

-fully open aperture (f/2.8)

-point strobe and lens at a wall about a meter away

-take a picture

pass = strobe fires a very short flash and recycles very quickly

fail = full dump

Part B "subject too far away for your strobe's power"

-put the dome cover or lens cap on

-take a picture

pass = full dump and strobe has to recycle fully

(I think, S&S strobes have a LED that tells you if a full dump occurred or if TTL quenched it before a full dump)

Correct exposure and TTL are many times mutually exclusive (especially, in wide angle); it can work very well for macro.

Be very careful with the reflectivity of your subject:

-octopi, moray eels eat up light

-barracuda, the underside of mantas reflect light back

TTL generally assumes the main subject has 18% gray reflectivity (and makes stupid mistakes because of it)

Use:

-histograms

-blinky black over exposure warnings

To catch exposure errors and fix them.

Take Care,

ChrisS

Hi Andrew,

Thanks for your reply.

But this is my point; shouldn't all the exposures turn out the same if the TTL conv. is working??

If it is a large opening (small #) then the TTL conv., should quench the strobe quickly.

If it is a small opening (large #) then the TTL conv., should allow the strobe longer before quenching.

I will assime a shutter speed of 1/60 so the strobe has plenty of leeway...

Am I missing something here, or am I on the right track...

Bruce...

Bruce,

But this is my point; shouldn't all the exposures turn out the same if the TTL conv. is working??

Yes. And as Chris says, it may not mean the exposure is correct, but it should be somewhat consistent. If you can use a gray card or something close to 18%, you will at least know if the TTL is working as it should.

If it is a large opening (small #) then the TTL conv., should quench the strobe quickly.

Yes.

If it is a small opening (large #) then the TTL conv., should allow the strobe longer before quenching.

Yes

I will assime a shutter speed of 1/60 so the strobe has plenty of leeway...

Strobe sync is more a characteristic of the camera rather than the strobe. D70 (and I assume the s, too) has a sync speed up to 1/500. It is all do do with the speed of the shutter itself.

Am I missing something here, or am I on the right track...

Sounds like you are on the right track. Just do it.

Bruce, TTL will work properly over around 5 stops. If the aperture is too large, the strobe might not quench quickly enough, thereby overexposing slightly. If the aperture is too small, ttl cant give the strobe more power then it actually has, so it will underexpose.

the green light will probably mean it quenched: keep in mind that when you try stuff in your room, your strobe will have more power then in the water...

I tend to do TTL tests by setting the shutter speed to the synch speed - on a D70s you can use 1/500 - then take a series of shots of a subject starting at F2.8 and working my way up through all the apertures.

The aim is consistent exposures over a range of apertures.

I last did a test on the Heinrichs converter in a pool last month. It worked really well from about F4 all the way to F22.

Alex

The quick and dirty way to just see if things are communicating with each other is to aim the strobes into the lens and shoot a full dump with TTL 'on' and then 'off'. If your coverter talks to your camera and strobes, there should be a night and day difference in the two images.

/c

Hi Guys,

I conducted a few 'tests' with the spartan equipment that I have available to me.

I first used the YS120 strobe and carried out "Christain's recommended test" and the results were a spectacular failure. The YS120 did a full dump at all times including when turned to manual. The only time that it didn't do a full dump was at 1/2 power. Interestingly when the TTL converter was still turned on, the YS120 refused to fire at full manual dump, but would fire at 1/2 power?

I switched to Andrew and Alex's suggested 'test protocol' and used a 18% grey card and switched apetures. Same results as with the previous test. Full dumps!

I then switched strobes to a YS90 Duo. When used with 'Andrew and Alex's Test' the YS90 was showing consistent exposures during the switches. It wasn't always correct but at least it was trying to get it right.

As I said in my first column, these tests were carried out with a S&S MK I (Nikon) converter and as noted they have since released two upgrades to the open market.

Maybe someone from Sea and Sea would like to step forward (finally) and help us end users out with an update on what we are supposed to do with these 'early' pieces of shit that never work; and don't seem as if they ever could???

Just the ramblings of a cranky colonial...

Bruce...

Hi Guys,

I conducted a few 'tests' with the spartan equipment that I have available to me.

I first used the YS120 strobe and carried out "Christain's recommended test" and the results were a spectacular failure. The YS120 did a full dump at all times including when turned to manual. The only time that it didn't do a full dump was at 1/2 power. Interestingly when the TTL converter was still turned on, the YS120 refused to fire at full manual dump, but would fire at 1/2 power?

I switched to Andrew and Alex's suggested 'test protocol' and used a 18% grey card and switched apetures. Same results as with the previous test. Full dumps!

I then switched strobes to a YS90 Duo. When used with 'Andrew and Alex's Test' the YS90 was showing consistent exposures during the switches. It wasn't always correct but at least it was trying to get it right.

As I said in my first column, these tests were carried out with a S&S MK I (Nikon) converter and as noted they have since released two upgrades to the open market.

 

Maybe someone from Sea and Sea would like to step forward (finally) and help us end users out with an update on what we are supposed to do with these 'early' pieces of shit that never work; and don't seem as if they ever could???

 

Just the ramblings of a cranky colonial...

 

Bruce...

That sounds frustrating Bruce. According to Sea&Seas website, YS120:s should be compatible with all their converters (I,II and III). Is it possible for you to borrow another 120 from a friend or dealer, just to rule out that there is something wrong with yours? Did you try to shoot the YS90 into the lens in manual and TTL?

Also, with some converters there has been reccomendations to turn things on in a certain order, first the converter, then turn the strobe(s) on and then off, then turn the camera on and finally turn the strobe(s) on again. Don't know if there are such reccomendations with the Sea&Sea converters?

And when i re-read my post I understood that I expressed myself in a way that left room for interpretation. When I say TTL 'off', I don't mean to switch the converter off, but to put it in manual mode, so the two comparison shots should be made with your system set to:

1. Manual strobe control and full power on the strobes

2. TTL strobe control

good luck