S & S YS 90 TTL Auto

I did ask about this in another thread with no replies so I thougt I would try it as a new topic.

Has anyone tried this new S & S with a digital SLR? While it is pretty obvoius that you are not exactly going to get correct exposure simply by matching the f stop setting of the strobe with that of the camera as sugested by Sea and Sea, it seems to me that you would have a covenient manual " output controller " by changing the varying F stop setting on the strobe to get correct exposure.

Any comments?

Charlie Hood, a D100 user, reviewed it in the UK's DIVE magazine.

S&S AUTO review

Thanks for the source Alex.

It appears to be a a rather favourable review I must say. The only downsides mentioned were the price and the rare overexposures of very white subjects ( which is the case with TTL anyway)

I still find it hard to understand how the strobe can figure out correct exposure particularly because the strobe to subject distance is obviously not the same as the camera to subject distance.

I also wonder what happens when you use two of these together. Any ideas?

How "reliable" source is the UK Dive magazine? Seems that Oly C-5050 is the _worst_ pocketable digital UW camera in their other review. Huh.

In the strobe's case I would say very reliable. The Hoodster knows what he is talking about when it comes to cameras. From memory (and I could be wrong) I don't think that Charles did the review on the compact cameras. I think with regular equipment testers they will always try to do the best job they can - afterall they have to survive in the industry!

Mr Hood has owned and used both compact and SLR digital camera underwater - and I think is a good source.

Speaking synically, I guess with all magazines it is important to remember which companies have large advertising revenues. In car magazines you will rarely see a motor panned if that company has a big advert on pages 1 & 2!

Alex

I still find it hard to understand how the strobe can figure out correct exposure particularly because the strobe to subject distance is obviously not the same as the camera to subject distance.

Hi Andre,

I saw your post and it may be just the way you wrote it, but it looked like you had a slight confusion about lighting. Always bear in mind, that the exposure of a subject lit in a given way is pretty much constant never mind what the distance that subject is from the lens. Thats how the auto strobes work, they are basically strobes with built in "spot meters".

Lets say you have a subject which is reference grey (18%), If it is correctly exposed, then the captured tone is 18% grey. Now if you light it with an auto strobe, dialled to f/8 say, then you will need to set your aperture to f/8 for that grey tone to be rendered correctly.

This is a simplified case for clarity, in real life you have issues with surfaces having strange reflective properties, but its a good starting point.

I notice that Charles Hood makes an odd statement, which sounds like a typo or a misunderstanding of exposure on his part:

In manual mode the flash delivers maximum power for each shot. The camera’s aperture has to be estimated by how far the subject is from the lens.

I'd have to say that's wrong, and you need to base the aperture calculation on the distance from strobe to subject, but luckily these are often quite similar.

I hope I've added to your understanding, rather than your confusion. If in doubt, go back to first principles, I would recommend for anyone to read "Light - Science and Magic" by Hunter and Fuqua.

Have fun

Martyn

I'm not sure about that Martyn,

Imagine the extreme case if you will, where the strobe is 1' from the subject, but the camera is 3' away. The sensor is in the STROBE, so it will fire off at a power to get a good exposure if the camera is 1' away. WRONG. The light path is actually 4 feet, but the strobe doesn't know that.

Therefore, the shot will be underexposed. The strobe (In My Opinion) should always be the same distance from the subject as the camera to get proper exposure w/ this unit.

Cheers

James

Hi James,

I'm not sure I get your reasoning here. Why would you expect the exposure of the subject to be significantly affected by the subject to lens distance? Does water clear enough for photography attenuate light that much?

Certainly in clear water or air, the subject to lens distance is irrelevant to exposure.

If light fell off significantly with distance, then I would expect the reef to fall off to black as I looked along the reef wall.

I hope I'm making sense, coz you've got me puzzled now.

Regards

Martyn

Yes.

The camera to subject distance is one of three of THE most important factors in lighting.

Guide Number = Fstop * Distance

Distance in this case is generally held to be the camera to subject distance, with the assumption that the flash isn't too far away.

Light follows the 1/r^2 rule underwater just like it does above water.

Cheers

James

Just to say thankyou to Andre for bringing up this strobe. Having had a good think about the way one would use the device has actually convinced me that it might suit my needs quite well.

I would really like to hear how well it works as fill for wide angle shots. I have to assume in this case that it will often not be able to supply enough light to match the dialled aperture, as the strobe to subject distance will often be too large for the sensor to receive enough light back to actually quench the strobe. In this case the gun will simply operate at it's max Guide No. and bingo, you are back in manual territory.

So an interesting product, I can definitely see the appeal for macro and moderately close range.

I would assume you could use any strobe you would normally use in TTL Slave mode with the YS90 Auto, as long as it was not pointing at the Auto sensor (this could cause premature quenching).

Thanks for the mental exercise Andre,

Cheers

Martyn