SF20 operation question

[simon_wong]

Hi,

 

Have a used SF20 with no manual.

 

Wondering about the LCD display when in TTL mode.

 

When I change aperature on my lens no corresponding display changes

occurs on the LCD readout. Is something wrong with my flash?

 

I can change things with the +/- buttons on the flash, but this seems

independent of the lens aperature.

 

Confused.

[phillip_p]

What camera are you using this with? With the M6TTL you have to set the aperture on both the lens and the flash.

[simon_wong]

Thanks Phillip.

 

I have the M6TTL. I gather then the flash does not sense the lens aperature automatically like it does the ISO setting?

 

Also, does anyone know if the TTL gives a better or worse result compared to A setting at the 3 preset aperatures?

[xav]

Assuming you're using an M6 TTL, when the flash is set to TTL mode, the only thing the LCD screen gives you is the maximum distance your flash can reach. As you said, ISO is directly transfered to the flash, but you do have to set the aperture manually, if you care about getting the max distance displayed. Otherwise just shoot.

 

FYI, when I use the SF20 to shoot people, their faces are overexposed to my taste: I generally reduce the SF20 output by 1 stop.

[phillip_p]

When you lightly touch the shutter button (if the flash is in TTL mode) the LCD should display the aperture setting. You then can match the lens and the flash setting. Usually I add one more stop just like Xavier does since the faces seem to get wash-out.

[phillip_p]

sorry I stop-down the lens one more stop instead of reducing the flash output by one stop.

[jay_.]

As has been said, the SF20's LCD panel receives no information as to the lens aperture set on an M6TTL or M7 because there is no coupling between the lens aperture and the body to transfer this info. For indoor flash I can't see any difference between "A" mode and TTL, probably because the angle of metering is nearly the same, but the TTL mode is more convenient because it permits the choice of any aperture. Outdoors for fill-in, the TTL is certainly more convenient for the same reason, and I dial in 1-2 stops minus compensation. Unless I am using the 135mm lens I always leave the wideangle diffuser on as it softens the light a little. I cut the bottom half of a little rectangular plastic bottle my wife had from hand lotion, and it just press-fits the silver bezel around the SF20 flashtube, basically a homemade StoFen Omni-Bounce.

[alain_besancon]

Simon,

 

With my English ... I hope to help you:

- in TTL mode with M6 TTL, the 2nd lightmeter stops the flash light when the light on the film surface is OK (but "global" measurement)

- the screen tells you the distance covered by the light:

+ if your main topic is at closer distance, shut 1 (evently 1,5) step aperture more

+ if your main topic is at highter distance, open 1 step (evently ...) more

More difficult, a portrait at short distance with a distant background ...? May be it would be better to reduce the power of the flash (for the face) and open more the aperture for background ...

Here some other advices would be fine.

and it would be fine if you understand what I try ... ;-)

Regards, Alain

[jackflesher]

<i> With the M6TTL you have to set the aperture on both the lens and the flash. </i> <p>

 

This is a common misconception, but is untrue. In TTL mode all you need to do is mount the flash, turn it on, set the flash to TTL mode, set the shutter-speed on the camera to 1/50, set your lens to whatever f-stop you want to shoot at, and the internal electronics will cut the flash off at the exact time needed for accurate exposure. As has been stated already, the only reason to transfer an f-stop to the SF-20 in TTL mode is to see what the max distance is for that f-stop with whatever speed film you have loaded. <p>

 

Cheers, <p>

[doug_lee__cinnaminson__nj]

"sorry I stop-down the lens one more stop instead of reducing the flash output by one stop."

 

I don't believe that is going to work if the SF-20 is set to TTL mode.

 

-Doug

[george_b1]

But, you can only put in three aperture stops: 2.8, 5.6, and 11. If you want to use the flash in the Auto mode, you'll have to set one of those three apertures on the camera, also on the flash, and dial in the film speed. (Remember, he doesn't have a manual)

[lutz]

Simon (and some of you posters),<P>I sense some confusion about what the SF20 is actually capable of in its three modes. I'll try to explain how I see it.<P>Basically, it works at three levels of "intelligence".

<P> 1) Manual mode: The SF20 acts like, okay, my guide no. is 20 @ ISO 100 and my output will always be *maximum*, so you better dial in the ISO and the distance and the amount of over-/underexposure you wish. All I can do for you is calculate the correct f-stop (based on the simple equation: 20 divided by distance in meters equals f-stop) and show it on my display. But you better set it on the lens yourself.<P>2) Auto mode: Hey, I've got an eye to spy on your subject, the one beneath my name. If you promise to set the aperture accordingly (and I give you a choice of three - 2.8, 5.6, 11) I will *reduce* my output perfectly according to what my eye sees. I have a very straight eye though, so you better point me straight towards your subject. But you may still influence my calcs by dialing in different ISO or over-/underexposure values.<P>3) TTL mode: Well, your Leica TTL has the better eye. I'll let her take over the measuring (and with the help of a dedicated cord you point me any direction you chose!). And as soon as she's seen enough light on the film plane I'll interupt my output. You may influence my calcs by over-/underexposure values, but you won't be able to tell me a different ISO than the one you dialed in on the lady.<P>As for over-/underexposure values, you have to take into account that the SF20's eye (as well as your Leica TTL's) is as dumb as any exposure meter, i.e. calibrated to 18% gray. So, if this is not the brightness of your subject or the brightness you want it to be reproduced with, you better work on the dummies...;o) This is most recommendable for fill-in where I usually underexpose by 1 1/3 to 2 stops and mandatory for night shots, where the dumb meters integrate dark backgrounds into their calcs.<P>Hope that helps a bit. Cheers.<P>PS. Jack, as always, you have been the most straight forward. Just a slight remark: Setting the shutter to 1/50 isn't mandatory. Any longer exposure will work, too. And can be most welcome especially if you wish to preserve low level ambient light. The short flash exposure will take care of freezing the foreground.<P>PPS. The SF20 is a terrific little brother to the Leica M. Enjoy.

[lutz]

Addendum.<P>While doublechecking the Manual mode (the one I never really use...) I noticed that the SF20 will well give you a choice among 1/1, 1/2, 1/4 and 1/8 of maximum output! I.e. 0, 1, 2, 3 stops less than maximum. It will re-calculate the (shorter) distance for correct exposure, though. So, if you wish to underexpose you either ignore the new distance displayed and keep in mind that, for instance, twice the distance equals a quarter the exposure (i.e. 2 stops) - or you dial in another f-stop until the SF20 displays the correct distance again and you then "cheat" exposure by closing/opening the aperture on the lens.<P>Once again, this is harder to put in words than into practice. The SF20 is highly instructive and will teach you a lot about flash photography - or will let you forget about it completely, in TTL mode - as you prefer.

[george_b1]

Lutz -

That's the clearest explanation I've ever seen about how the SF20 works in each mode. Thanks!

[simon_wong]

Thanks guys. I think I've figured it all out. Everyone's feedback

helped, especially Jack and Lutz's

 

Cheers.