Sync issue between SF40 and M262

[leicauser89]

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I have an SF40 flash (brand new) and an M262 that I have had since 2021. Before the SF40 I have been using a third party flash on manual mode. I purchased the SF40 because I wanted the TTL capability. It should be noted, before I say anything further, that the SF40 works as expected at all aperture/ISO settings when set to manual mode. However, this is no different from any other flash setup I have, so the SF40 doesn't do anything different when used as a manual flash (except existing as a flash that is smaller than my other flash units).

 

However, on TTL mode, there are specific aperture/ISO settings at which the flash does not register in the picture. The flash fires, but the image is not illuminated. I have removed the lens and recorded the flash/shutter at 240fps to see if they're out of sync and it appears that, at specific settings, they are. The flash will fire before the shutter is open but not during. I am hoping you can enlighten me.

 

I am using a 28mm 2.8 Elmarit ASPH lens. It is fully attached and recognized by the camera when set to automatic detection.

 

My camera settings are as follows:

DNG only (no JPG)

Auto WB

Exposure bracketing and compensation: Off

Flash settings: start of exp. / auto slow sync. 1/focal length

 

On a tripod, without moving the camera, and shutter set to 1/60, I tested the flash (on TTL) at all available aperture and ISO settings and a pattern emerged:

 

At f/2.8, f/3.3, f/16, f/19, and f/22 the flash fires reliably and properly at all ISO settings.

At f/4, f/4.8, f/5.6, f/6.7, f/8, f/9.5, f/11 the flash fires reliably up through ISO 400. Beyond that the flash did fire, but did not illuminate the frame.

At f/13 the flash did fire and illuminate the frame up through ISO 400. Above that it fired and illuminated the frame at ISO 800, 1600, and 3200. It fired but did not illuminate the frame at ISO 500, 640, 1000, 1250, 2000, 2500, 4000, 5000, and 6400.

 

Switching the flash to A mode, I tested a few apertures with the full range of ISO settings. The apertures tested were f/2.8, f/4, f/11, f/13, and f/16. The results were exactly the same, except for those at f/13. At f/13, instead of working at select ISO settings (as in the TTL test), above ISO 400 the flash did NOT illuminate the frame.

 

When operating the camera handheld at various angles it does occasionally fire correctly and illuminate the picture when in the tests it consistently did fire, but did not illuminate the picture. Additionally, it should be noted that the flash TTL is still unreliable at all apertures at f/4 and smaller at all ISOs above 400. It will sometimes illuminate the frame and not others, but the predominant result is that it does not illuminate the frame.

 

Again, the flash IS reliable at all settings when used in M mode and these issues arise only with TTL and A modes.

 

Can you please help me understand why this may be happening? I would expect TTL to work successfully at all ranges.

 

Additionally, at f/2.8 and ISO 6400, the flash does NOT fire at minimum power. At f/2.8 and ISO 6400 and the flash set to 1/256 power the image is certainly overexposed, but when I set the flash to TTL the flash chooses a power above its minimum power further overexposing the image. I would expect the flash to choose its minimum power when set to TTL (which it does not) because the image is overexposed even without the flash.

AD56B4F9-1D74-49EE-BC00-64C0FDC7BA18.heic

Edited January 8, 2024 by leicauser89

[hepcat]

I have only one thought...  have you cleaned your hot shoe contacts recently?  If so, disregard everything past hello, but if you haven't perhaps you might try a test after cleaning them and see what happens.  

[leicauser89]

4 hours ago, hepcat said:

I have only one thought...  have you cleaned your hot shoe contacts recently?  If so, disregard everything past hello, but if you haven't perhaps you might try a test after cleaning them and see what happens.  

Unfortunately, yes, I have done that several times. The results of my tests were repeatable and held the pattern you see in the chart I created. After running the whole test I randomly selected numerous settings combinations and there were no changes. The only change occurred when handheld, but the results were still that in combinations that are marked in black the predominating result was no illumination regardless of how I held the camera.

[hepcat]

9 hours ago, leicauser89 said:

Unfortunately, yes, I have done that several times. The results of my tests were repeatable and held the pattern you see in the chart I created. After running the whole test I randomly selected numerous settings combinations and there were no changes. The only change occurred when handheld, but the results were still that in combinations that are marked in black the predominating result was no illumination regardless of how I held the camera.

Well, then my professional, technical opinion is that somethin' ain't workin'.  Sorry... that's the best I've got.  Hopefully someone with more technical expertise can help you out with some useful advice.  Good luck!

[sometimesmaybe]

@leicauser89 any chance you can post the images in JPG? windows doesn't the Mac images

[Luke_Miller]

I have the SF-40 and use it with my M240.  In TTL mode the SF-40 will always fire a pre-flash and use the data from the pre-flash to calculate the correct flash exposure when the shutter opens.  If the camera's metering finds there is already sufficient ambient light for a "correct" exposure the flash will not fire while the shutter is open.  I suspect that is what you are seeing.  The metering in my M240 is very sensitive to light sources in the frame, so even in a darkened room a light fixture may be enough to prevent the flash from firing.  The same issue can exist with a back lighted subject. The bright background will result in no flash and significant underexposure of the subject.  Manual flash with the SF-40 (and the other current Leica flashes) is the solution.  A Mode on the SF-40 is a variation of TTL and produces similar results.  A Mode on my SF-58 Metz produced flash is Auto-Thyristor (the flash controls the flash part of the exposure independent of camera metering) and works well in situations where TTL fails.  

Edited January 19, 2024 by Luke_Miller

[leicauser89]

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@Luke_Miller

Thanks for the detailed response! I am noticing the pre-flash with no follow up flash when the flash doesn't register in the image and two flashes when it does (mostly—sometimes they're so quick together that I can't really see it). Overall that does make a lot of sense for the results. I do remember that there was some instances where I purposefully overexposed the image with a high ISO and the flash still fired and registered in the resulting image. The TTL also worked at apertures near fully open and near fully closed (around f/2.8 and f/22) at ALL ISO settings, but not those majority of apertures between past ISO 400. When I consider that pattern, I'm not fully convinced by it being a metering issue. But, maybe I'm still misunderstanding something...

Because the only advantage of the SF40 without (what I would consider) reliable TTL functionality (that it won't fire on correct or over-exposures or with other bright light sources in frame) and its best use being on manual, the only real advantage it retains is it's size. I find it ridiculous that another light source would prevent the flash from firing since I probably WANT the flash to fire in addition to the light sources present, even on proper exposure. That's the whole point of using a flash to fill (for me). The results of my tests on A mode matched the TTL results exactly. I don't know how the A mode works on the SF40, maybe you'd be able to enlighten me, but in practice it appeared to have no difference in results. Using a non-Leica flash with auto-thyristor or just plain 'ol manual seems the way to go. Unfortunately I returned the flash since I've been unable to figure this out, even with Leica technical support.

Edited January 19, 2024 by leicauser89

[Luke_Miller]

The M240 is the latest M model I've shot with, possibly later models do better with TTL flash exposure control.  My M8.2 and M9 were equally problematic. Since my other camera system is Nikon, I am keenly aware of how good TTL can be.  I've learned to work around the SF-40/M240 idiosyncrasies due to the flash's size and weight.  I believe the issue is the primitive flash metering function in the camera rather than the flash. I notice that the times the flash image is underexposed an image taken without flash will generally be also. The SF-58 works well as do my Nikon flashes in Auto Mode, but they are big, heavy, and really affect the handling of an M body.  I believe A Mode on the SF-40 disables the ability to use the exposure compensation dial.  The SF-24D works well in Auto Thyristor mode but does not tilt or swivel. Thus, it only produces the direct flash that gives flash photography a bad name.  There may be other third-party flashes, similar in size to the SF-40 that will work, but very few current production flashes offer Auto Thyristor mode.

I use bounced flash exclusively, since it produces light off axis to the lens/subject with soft shadows.  Using manual flash settings with bounce is fairly easy, since correct flash exposure is not dependent on camera to subject distance but rather the combined flash to bounce surface and bounce surface to subject distance.  Takes more flash power, but a larger area is illuminated that is less demanding on precise power settings.

Edited January 20, 2024 by Luke_Miller

[hepcat]

On 1/9/2024 at 3:28 PM, sometimesmaybe said:

@leicauser89 any chance you can post the images in JPG? windows doesn't the Mac images

Here's his file as a .jpg

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[leicauser89]

Thanks, @hepcat! I'm sorry I was confused by your request, but I understand now!