Some Leica S flash questions (SF20, SF58, SF64)

[swiss leica fan]

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I bought the SF64 only last week and have the S007. So far I like the combination - exposures are consistent and my impression is that the pre-flash sequence in TTL is faster than it was with the SF-58. And I like the LCD touch display, too.

I am not sure I understand your question, though. When you use the CS lenses (with the shutter set on CS), the flash stays in the TTL mode until the max sync speed of the leaf shutter (1/1000s); then it switches to TTL-HSS. When you use non-CS lenses, the flash switches from TTL to TTL-HSS at any shutter speeds faster than the max sync speed of the focal plane shutter (1/125s). The advantage of CS lenses here is the same as with any other flashes - speedlites or strobes - they allow faster sync speeds to control ambient light more efficiently (through faster shutter speeds) or use your lenses at wider aperture settings (to achieve shallower depth of field) without having to use ND filters. In summary:

(i) with non-CS lenses - your fastest sync speed is 125/s, which may be too slow, depending on how much ambient light there is and/or how wide an aperture you want to use - you can use HSS (however that reduces the power of the flash significantly) or an ND filter, to address this.

(ii) with CS lenses - you can use the maximum power of your flash until 1/1000s, to "overpower" the ambient light.

A typical scenario may be a sunny day, where your ambient exposure (at ISO 100) would be say 1/500s @ F8.0. With a CS lens, you can happily sync the flash at that shutter speed, or even 1/1000s @F5.6. With a non-CS lens, you would have to sync at 1/125s which would require you to use F16, or a 3-stop ND filter to get you back to F5.6. ND filters can be a PITA, not just screwing and unscrewing them but they also impair your (and the AF-system's) ability to focus properly. HSS can be helpful, but only at much shorter distances than when the flash can operate on full power (and bear in mind that any modifiers or bouncing your flash will reduce power even further).

As for the slave function - you can operate the flash in slave function with both S and CS lenses. What is your thought regarding 1st and 2nd curtain sync here? A typical use for 2nd shutter sync would be at slower shutter speeds (e.g. 1/30s) where some moving ambient light sources (e.g. car lights, torches held by moving dancers etc.) register on the sensor first and the exposure is then finished (movement frozen) with the flash. The light streaks from the ambient light sources are shown "behind" the object, e.g. the light streaks follow a moving car, whereas they would show "in front", if you used 1st curtain sync. In other words, you would usually not use 2nd curtain sync at the (high) shutter speeds that require CS lenses for flash syncing, because, if you were, you would be giving the ambient light sources too little time to create the "streaks" that are meant to symbolise movement in your photo. Maybe I am missing something here?

 

This is a very good explanation. However, I did not understand the ND filter argument. In my view using ND filters for daylight flashing does not resolve the problem of not having fast enough sync speeds. This is because the ND filter does block the daylight as it does block the flash light. Doing flashlight portraits in sunlight demands either fast sync speeds and/or strong enough flashlights to get the right balance between sunlight and flashlight. A HSS flash is a remedy but it is only a partial solution as it costs flash power and works only at short distances.

 

Kind regards

Swiss Leica Fan

Edited October 24, 2016 by swiss leica fan

[albireo_double]

This is a very good explanation. However, I did not understand the ND filter argument. In my view using ND filters for daylight flashing does not resolve the problem of not having fast enough sync speeds. This is because the ND filter does block the daylight as it does block the flash light. 

 

 

You need to increase the flash output correspondingly, when you bring down the ambient exposure with an ND filter. 

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[BigBabyEarl]

I bought the SF64 only last week and have the S007. So far I like the combination - exposures are consistent and my impression is that the pre-flash sequence in TTL is faster than it was with the SF-58. And I like the LCD touch display, too.

I am not sure I understand your question, though. When you use the CS lenses (with the shutter set on CS), the flash stays in the TTL mode until the max sync speed of the leaf shutter (1/1000s); then it switches to TTL-HSS. When you use non-CS lenses, the flash switches from TTL to TTL-HSS at any shutter speeds faster than the max sync speed of the focal plane shutter (1/125s). The advantage of CS lenses here is the same as with any other flashes - speedlites or strobes - they allow faster sync speeds to control ambient light more efficiently (through faster shutter speeds) or use your lenses at wider aperture settings (to achieve shallower depth of field) without having to use ND filters. In summary:

(i) with non-CS lenses - your fastest sync speed is 125/s, which may be too slow, depending on how much ambient light there is and/or how wide an aperture you want to use - you can use HSS (however that reduces the power of the flash significantly) or an ND filter, to address this.

(ii) with CS lenses - you can use the maximum power of your flash until 1/1000s, to "overpower" the ambient light.

A typical scenario may be a sunny day, where your ambient exposure (at ISO 100) would be say 1/500s @ F8.0. With a CS lens, you can happily sync the flash at that shutter speed, or even 1/1000s @F5.6. With a non-CS lens, you would have to sync at 1/125s which would require you to use F16, or a 3-stop ND filter to get you back to F5.6. ND filters can be a PITA, not just screwing and unscrewing them but they also impair your (and the AF-system's) ability to focus properly. HSS can be helpful, but only at much shorter distances than when the flash can operate on full power (and bear in mind that any modifiers or bouncing your flash will reduce power even further).

As for the slave function - you can operate the flash in slave function with both S and CS lenses. What is your thought regarding 1st and 2nd curtain sync here? A typical use for 2nd shutter sync would be at slower shutter speeds (e.g. 1/30s) where some moving ambient light sources (e.g. car lights, torches held by moving dancers etc.) register on the sensor first and the exposure is then finished (movement frozen) with the flash. The light streaks from the ambient light sources are shown "behind" the object, e.g. the light streaks follow a moving car, whereas they would show "in front", if you used 1st curtain sync. In other words, you would usually not use 2nd curtain sync at the (high) shutter speeds that require CS lenses for flash syncing, because, if you were, you would be giving the ambient light sources too little time to create the "streaks" that are meant to symbolise movement in your photo. Maybe I am missing something here?

Thank you! I'm not really that well versed in flash photography. Very helpful. So essentially for say the 100 S which is not a CS I could use this flash in TTL-HSS and still be at higher shutter speeds. How much loss is there?

 

Can non cs lenses use the flash in slave mode? Basically making it a small portrait kit?

 

With a CS lens in the sun wouldn't 1/1000 still require ND or going to TTL-HSS if you wanted to shoot wide open outdoors?

[swiss leica fan]

You need to increase the flash output correspondingly, when you bring down the ambient exposure with an ND filter. 

Yes, this is what I meant. You need faster central shutter speeds or/end stronger flash lights. An ND filter does not help as it does not allow you to selectively block the sunlight. Instead it also blocks the flashlight.

[swiss leica fan]

Thank you! I'm not really that well versed in flash photography. Very helpful. So essentially for say the 100 S which is not a CS I could use this flash in TTL-HSS and still be at higher shutter speeds. How much loss is there?

 

Can non cs lenses use the flash in slave mode? Basically making it a small portrait kit?

 

With a CS lens in the sun wouldn't 1/1000 still require ND or going to TTL-HSS if you wanted to shoot wide open outdoors?

 

A TTL-HSS 58 or 64 should be sufficient for portraits at sunlight with the 100S. I have achieved also good results with the 30S. You have to experiment a bit to find the right balance between the background and the foreground that is illuminated by the flash. I realized that relying on the automatic exposure and automatic of the flash does not always work, rather you have to adjust the setting on the flash to find the right balance, ie in most cases to manually reduce the power of the flash.

 

However, the flash sticks with the camera unless you use a Nikon flash cable which should work with the Leica flashes as they have the same connector design. As far as I know TTL-HSS does not work in slave mode. Rather you need a studio flash equipment with battery back. With studio flash the CS lenses work perfectly well, again in manual mode with experimenting to find the right balance.

 

With a CS lens and 1/1000s sync speed you gain three stops which is a lot as it will help you to more than double the distance to your object.

[albireo_double]

Yes, this is what I meant. You need faster central shutter speeds or/end stronger flash lights. An ND filter does not help as it does not allow you to selectively block the sunlight. Instead it also blocks the flashlight.

You are right, I was thinking in the context of strobes (something like Profoto B1 which has 500WS, or stronger) - there you can use the ND filter to bring down the ambient and compensate with higher flash output to achieve correct exposure of the main subject, of course depending on how much ambient light you have, what aperture and modifier you are using. I haven't tried this with the SF-64 (probably something like 70-80WS), so don't know if (and at what distances) it would cope.