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TTL vs Manual Flash


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I'm using an M6 TTL and trying to understand some things about using it with SF24D flash.

 

Am I right in thinking that TTL flash fires the flash at full power and cuts it off when sufficient light has reached the film?

 

And if that is correct, might I be less obtrusive (ie not startling people with full power flash) if I use manual flash with the correct distance dialled in on a lower power setting?

 

Thanks!

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The TTL circuit will shut the flash off when sufficient light has reached the sensor.  When using the flash with a TTL enabled camera, it will recognize the ISO then you can adjust for the f stop.  You can also adjust for plus or minus output in EV mode.  You can use manual mode and make the calculations or there is also AUTO mode which the sensor in the flash itself will determine when there is enough light.  The green indicator light will give you a good idea if there has been sufficient output for the exposure.  A couple of test firings of the flash will give you a good indication if the setting is correct.  In the viewfinder the lighting bolt will flash when the TTL circuit has received a sufficient amount of light.  Test a roll and get a better idea.  As I mentioned in a previous posting the SF-24D is a good little flash, it just takes a little work to know how to use it properly.  Good luck and welcome to the forum, it's a great place for answers.

Edited by madNbad
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Thanks.  I've been experimenting in manual with reasonable results. I've been reducing the output until the flash shows the distance to my subject. The only difficulty is that I want to work quickly and haven't got time to change the distance. I thought I might try TTL mode so I don't have to work out the distance.  But I'm shooting pretty close and I'm worried about a full power flash in someone's face. 

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Thanks for this post, as I've been wondering about the same thing! However, I am deciding between the SF-20, and the SF-24D. The price difference is reasonably significant, roughly $100 USD apart, and was wondering if there are any significant reasons to pay extra. As far as I know, the SF-24D will work with digital Leicas, but I too am using an M6 TTL, and don't plan on using it for a digital body. In that case, would the SF-20 be better choice?

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Either one will work just fine on the M6 TTL.  The output is just about the same and all of the controls are similar.  Both are small and light enough so the camera will not feel unbalanced.  The drawback to both is the lack of an adjustable flash head.  A SF-20 is a good bargain for the occasional time when you would like to add flash and don't want to spend a lot of money.  The SF-20 was initially released at the same time the M6 TTL was introduced.  One accessory I can recommend for either flash is the Leicagoodies S-Fil.  It works well as a defuser and it folds flat for storage in your bag when not in use.  Output isn't dramatically affected and it softens the direct flash effect.

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I've been continuing to use the SF24D with my M6 TTL.  One thing I've noticed is that if I advance the film using after taking a photo, the flash fires again. But if I wait a few seconds, it doesn't. 

 

Any my ideas why this is happening?

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Sounds like a short in the hot shoe.  The best way to test it is with an off camera adapter with a hot shoe and a PC cord.  This will take the flash off of the camera and if it happens when it's connected to the PC socket then the problem may be with the flash.

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The TTL circuit will shut the flash off when sufficient light has reached the sensor.

 

Interesting! The M7 and SF 24D works differently. It does a pre-flash which is read by the TTL, then produces a second, correct amount of flash.

 

Auto uses the flashes built in auto-thyristor which stops the flash when adequate light has been sensed.

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Pico, after much searching around what I have learned is of the four contacts on the hot shoe of the M6 TTL only three are active.  The M7 has HHS (and possibly pre flash) because it's circuitry continues to provide power to the flash during it's cycle.  The M6 TTL will trigger the flash but there is no power from the camera during the flash cycle.  I would love to hear from any member who has more information.  

Edited by madNbad
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  • 3 weeks later...

I would be very interested in knowing if the SF-24 fires a pre-flash in TTL mode on an M6TTL. This happened with my Canon Speedlite and I truly hated it. Does anyone know?

 

Pico, after much searching around what I have learned is of the four contacts on the hot shoe of the M6 TTL only three are active.  The M7 has HHS (and possibly pre flash) because it's circuitry continues to provide power to the flash during it's cycle.  The M6 TTL will trigger the flash but there is no power from the camera during the flash cycle.  I would love to hear from any member who has more information.  

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Thanks.  I've been experimenting in manual with reasonable results. I've been reducing the output until the flash shows the distance to my subject. The only difficulty is that I want to work quickly and haven't got time to change the distance. I thought I might try TTL mode so I don't have to work out the distance.  But I'm shooting pretty close and I'm worried about a full power flash in someone's face. 

But you can't see TTL flash, right? It happens to quickly that it appears to be just one flash.

 

I tip that I use is to flag the flash with a piece of craft felt (sort of like wrapping a tube around it) so that it will bounce where I need it to go but not blind people who may be near by. By flagging this way it also makes the flash "directional" aka "from the side" and so it's more flattering and larger light.

 

Google "black foamie thing" to see how it looks and works.

 

I'd only use TTL flash when the subject to camera/flash distance is changing...there's no way to do it right manually. Manual flash is for static subjects and umbrellas and softboxes.

Edited by rpavich
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Recently I was in a pinch for a friend's party I just used an old Nikon SB-24 I had. There's a distance/iso/f-stop calculator on the back of it so I just used that. I first checked it against a meter and it was within one-third of a stop. Impressive for an old flash!

 

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So I would set the f/stop on my lens, set my lens to the distance on the flash, and used my feet to focus. Worked pretty well and I found it fun since it was a bit of a challenge.

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I would be very interested in knowing if the SF-24 fires a pre-flash in TTL mode on an M6TTL.

 

I don't think so. The SF24 and M6TTL (and M7) work in classic TTL mode by reading the flash output off of the actual film surface and shutting the flash down when a suitable exposure has been reached. 'Pre-flash' is a digital necessity whereby a flash reading is taken off of the shutter curtains prior to opening the shutter (due to the difficulty of reading the output reflecting off of the shiny digital sensor).

Edited by wattsy
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Thank you very much Ian. That's logical to me. Perhaps my Canon speedlite pre-flashed with my 1N because of how that camera worked TTL-wise.

 

I don't think so. The SF24 and M6TTL (and M7) work in classic TTL mode by reading the flash output off of the actual film surface and shutting the flash down when a suitable exposure has been reached. 'Pre-flash' is a digital necessity whereby a flash reading is taken off of the shutter curtains prior to opening the shutter (due to the difficulty of reading the output reflecting off of the shiny digital sensor).

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Interesting! The M7 and SF 24D works differently. It does a pre-flash which is read by the TTL, then produces a second, correct amount of flash.

 

That is incorrect. The M7 and SF24 combination works via a sensor that reads the flash output directly off the film surface (when the shutter is open). There is no pre-flash in TTL mode. That is why you cannot use the M7's HSS function in TTL mode (only manual) – the shutter is never fully open at the HSS speeds and thus the TTL circuitry cannot take a reading off the film.

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Thank you for the clarification.  I knew the older TTL read off of the film plane to determine the correct amount of light.  Now is the fourth contact live on the M7?  If so what is its' purpose?  

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