single flash in TTL mode - Leica SF 24D Flash

[SOHODE]

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Hi I received a used Leica SF 24d flash and tested it with my m10. in ttl mode the flash double fires only sometimes but most of times it fires only once. Is this normal?

The seller said: "Flash is calculating accurate TTL with a first burst but this is not always needed. Characteristic of Leica TTL flashes on Leica Digital M."

Also I see in different apertures with TTL flash the exposure is a little bit different (but it's not like the ttl is not working)  my experience with Nikon flash on a Nikon camera was different though. The exposure with TTL flash and different apertures was very similar.

Since the flash has signs of disassembly I suspect it has an issue. Do you have a sf24d? does it double fire all the time in ttl mode? do the exposures with ttl mode and different apertures are equal? 

Edited December 6, 2022 by SOHODE

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[Siriusone59]

I don't know about the SF24D but I do have a SF40 and like yours sometimes it does a pre flash and sometimes it doesn't.  Maybe it is just to fast for me to notice?  I have found that on my m10r I tend to get more consistent results when I select a ISO, usually either 100 or 400 depending on what I think is needed for ambient lighting.  On my Q, I get good results without pre-selecting anything other than aperture.

I saw the picture of the scratched screw that you posted, thinking that it might have been worked on in the past.  It's just possible that it was done by a previous owner cleaning up after a battery leaked from being left in it for way too long.🤔  I did that same thing to one of my old Nikon flashes.

[SOHODE]

Interesting so you also experience the random pre-flashes.

So do you think the exposure difference is because I didn't set the aperture on the flash manually? I thought the flash should catch it when I change the aperture on the lens. If not so what's the difference between manual mode and ttl mode? 

Another thing I realized is the flash doesn't recognize the distance when I change the focus the distance on the LCD is still the same. I don't think if this is correct for SF24D and M10. My lens is Summarit 35mm f2.5. 

[Siriusone59]

1 hour ago, SOHODE said:

Interesting so you also experience the random pre-flashes.

So do you think the exposure difference is because I didn't set the aperture on the flash manually? I thought the flash should catch it when I change the aperture on the lens. If not so what's the difference between manual mode and ttl mode? 

Another thing I realized is the flash doesn't recognize the distance when I change the focus the distance on the LCD is still the same. I don't think if this is correct for SF24D and M10. My lens is Summarit 35mm f2.5. 

I guess I should have worded it differently, I didn't mean setting anything on the flash other than putting in TTL and leaving flash compensation at 0.  Sorry for the confusion.

[SOHODE]

Thanks for letting me know. I had a chance to test the flash one more time and realized the pre-flash is working on all the shots in TTL mode. As you mentioned sometime it's faster and that's why I didn't realize in the first try. In different apertures the exposure is pretty consistent through my test in TTL mode. But I realized sometimes it calculates/exposes slightly different (maybe a half stop or less) but never gets over-exposed and it's always in the correct range. So it seems the flash is working normally. Regarding the opening signs, they're not only on the screw. There are some opening signs on the body too. I was worried if it was repaired in a bad way it could potentially damage my camera but since it is working now I guess there's nothing to be concerned about?