Experiments with multiple slave flashguns in auto mode

[David Lal]

I am fond of using flash which I find a great creative adjunct. While I do have a CLS/iTTL capable SB800 I don't use it a lot because I find the user interface cumbersome. Instead I use the now 30-year old SB26. In fact, I use up to 4 of them together and I do so using their delayed slave auto mode.

In a recent thread somebody here mentioned that multiple auto mode flashguns can interfere with one another. I wondered whether mine did - and set about finding out and if so, to what extent.

I arranged a test in which one by one I brought 3 remote flashguns into play. These were optically triggered by an on-camera SB400 dialled down to -3 EV. I did this just before dawn so my study was quite dark.

This took some time and the sun was rising so I repeated the same series of tests.

This is easier to see if full size image is viewed

In a third test series I used just one remote SB26 but set it at respectively F5.6; F8 and F11 i.e. persuading it to emit more light while keeping the camera (D750) set at F8, ISO=400.

Frames 1E and 3D are controls with no remote flashgun to verify that neither ambient light nor the triggering SB400 were contributing much to exposure.

I am not quite sure in test series 1 and 2 whether I prefer frames C or D.

My conclusion is that no, multiple SB26s do not interfere with one another when used this way. That is not surprising as they were designed back in the 1990s to be used together. The SB26 was an expensive item back then, US$ 350. Mine cost via Ebay about GBP£ 40.

 

[Dak on cam]

I am fond of using flash which I find a great creative adjunct. While I do have a CLS/iTTL capable SB800 I don't use it a lot because I find the user interface cumbersome. Instead I use the now 30-year old SB26. In fact, I use up to 4 of them together and I do so using their delayed slave auto mode.

In a recent thread somebody here mentioned that multiple auto mode flashguns can interfere with one another. I wondered whether mine did - and set about finding out and if so, to what extent.

I arranged a test in which one by one I brought 3 remote flashguns into play. These were optically triggered by an on-camera SB400 dialled down to -3 EV. I did this just before dawn so my study was quite dark.

This took some time and the sun was rising so I repeated the same series of tests.

This is easier to see if full size image is viewed

In a third test series I used just one remote SB26 but set it at respectively F5.6; F8 and F11 i.e. persuading it to emit more light while keeping the camera (D750) set at F8, ISO=400.

Frames 1E and 3D are controls with no remote flashgun to verify that neither ambient light nor the triggering SB400 were contributing much to exposure.

I am not quite sure in test series 1 and 2 whether I prefer frames C or D.

My conclusion is that no, multiple SB26s do not interfere with one another when used this way. That is not surprising as they were designed back in the 1990s to be used together. The SB26 was an expensive item back then, US$ 350. Mine cost via Ebay about GBP£ 40.

Uh, your setup is "one to three flashguns evenly arranged in 90° arc around subject at 1m distance". And those flashguns are of equal type. So they should all fire for roughly the same duration when looking at the same scene and seeing similar contributions from the other flashes.

The latter does not appear to be quite the case, however. If I take a look at 2B, the hard shadow in the middle of the image is hardly brightened. That would suggest that flash 2 does not contribute significantly to the scene. My guess is that flash 2 sees the output from flash 1 better than vice versa, so flash 2 concludes quite earlier that the scene is bright enough and leaves flash 1 to finish lighting the scene.

--
Dak

 

[David Lal]

The latter does not appear to be quite the case, however. If I take a look at 2B, the hard shadow in the middle of the image is hardly brightened. That would suggest that flash 2 does not contribute significantly to the scene. My guess is that flash 2 sees the output from flash 1 better than vice versa, so flash 2 concludes quite earlier that the scene is bright enough and leaves flash 1 to finish lighting the scene.

That's a very good point DAK and I take it onboard.

However, it is clear that when flashgun 3 came into play the harsh shadow produced by gun 1 was indeed ameliorated.

I can think of two possibilities:

1. Gun 2, despite the settings might not be outputting the same amount of light as the other 2 guns.

2. Though each gun was spaced about 30° in the horizontal plane, guns 1 and 3 were at the same height off the floor as the teddy bear but gun 2 was in the middle on the floor pointing up at the teddy's nose.

I need to explore further. Thanks for responding.

 

[David Lal]

Some good points were made in the previous response which I resolved to research further. I thought perhaps, though the flashguns were all the same model, they were not all emitting the same amount of light, even though set up identically.

Secondly, I thought I could have been more careful in positioning the flashguns, especially with regard to vertical angle to the subject. Thus:

(View original file for clearer a better picture)

I found that yes, there were differences in light output per gun - although this was very slight. I was careful this time to get the height of the guns off the floor more or less the same. I've only got one tripod so used piles of books - Wahrig Deutsches Wörterbuch on top of course ;-) to support the flashguns.

I see clear differences in the handling of shadows depending on guns used and my opinion is still that these SB26 flashguns do not interfere with one another. I wanted a slightly darker image so then dropped camera aperture to F11, not the F8 at which I had set the flashguns.

All flashguns pointing at the subject is not normally the way I use them. Typically I will be bouncing off walls and ceilings, perhaps one behind the subject providing contre-jour or hairlight and only one coming direct to the subject.

 

[Dak on cam]

All flashguns pointing at the subject is not normally the way I use them. Typically I will be bouncing off walls and ceilings, perhaps one behind the subject providing contre-jour or hairlight and only one coming direct to the subject.

If you have equal flashguns with their sensors pointing at the subject and one pointing directly at the subject and the others bouncing, then the light contribution from the flashgun pointing at the subject will be dominating the ensemble: every flash gun sees essentially the same light it uses for judging when to switch itself off, so they will switch off at about the same point of time, making the bounced flashes contribute less to the total light on the subject.

Which may be what you want or not. Personally I'd just dial in manual power instead of trying to trick the automatic mode into doing my bidding. CLS actually doesn't do a bad job, so one possibility on a social event might be to just distribute a few slaves across the room in places where they are not directly visible and then shoot from wherever without bothering about the individual shots. The downside is that a single flash firing is less distracting than the communication and measuring lightning storm preceding the main flash.

--
Dak

 

[David Lal]

CLS actually doesn't do a bad job, so one possibility on a social event might be to just distribute a few slaves across the room in places where they are not directly visible and then shoot from wherever without bothering about the individual shots. The downside is that a single flash firing is less distracting than the communication and measuring lightning storm preceding the main flash.

Agreed. Actually, that is exactly what I do, especially for dinner parties and such like here at home, maybe using up to 3 remote SB26s dotted about behind ornaments and so on then use the diminutive SB400 on camera at the dinner table. It works very well. Lots of people feel intimidated if a large flashgun is pointed at them but will tolerate the SB400 (or indeed, inbuilt flash tube). Another downside of course is that my optically-triggered slaves will fire if somebody else takes a (flash) photograph.

The technique can work quite well even in the garden for wildlife:

Fox and SB26

Here's one showing the remote flashgun going off:

 

[Dak on cam]

CLS actually doesn't do a bad job, so one possibility on a social event might be to just distribute a few slaves across the room in places where they are not directly visible and then shoot from wherever without bothering about the individual shots. The downside is that a single flash firing is less distracting than the communication and measuring lightning storm preceding the main flash.

Agreed. Actually, that is exactly what I do, especially for dinner parties and such like here at home, maybe using up to 3 remote SB26s dotted about behind ornaments and so on then use the diminutive SB400 on camera at the dinner table.

It definitely isn't exactly what you do since SB26 is not capable of doing CLS, nor is the SB400 capable of acting as a CLS master. So you are setting up a fixed lighting scenario, not one that adapts itself to where you are shooting and pointing and focusing the camera.

It works very well. Lots of people feel intimidated if a large flashgun is pointed at them but will tolerate the SB400 (or indeed, inbuilt flash tube). Another downside of course is that my optically-triggered slaves will fire if somebody else takes a (flash) photograph.

With CLS, only if they use a Nikon set as master on the same channel.

The technique can work quite well even in the garden for wildlife:

Fox and SB26

Here's one showing the remote flashgun going off:

Cute.

--
Dak

 

[David Lal]

It definitely isn't exactly what you do since SB26 is not capable of doing CLS, nor is the SB400 capable of acting as a CLS master. So you are setting up a fixed lighting scenario, not one that adapts itself to where you are shooting and pointing and focusing the camera.

Ah, no - what I meant was the principle of dotting slave flashguns around the room. True the SB400 can't be a CLS master but can be used as iTTL around the dinner table.

 

[1971_M5]

The latter does not appear to be quite the case, however. If I take a look at 2B, the hard shadow in the middle of the image is hardly brightened. That would suggest that flash 2 does not contribute significantly to the scene. My guess is that flash 2 sees the output from flash 1 better than vice versa, so flash 2 concludes quite earlier that the scene is bright enough and leaves flash 1 to finish lighting the scene.

That's a very good point DAK and I take it onboard.

However, it is clear that when flashgun 3 came into play the harsh shadow produced by gun 1 was indeed ameliorated.

I can think of two possibilities:

1. Gun 2, despite the settings might not be outputting the same amount of light as the other 2 guns.

2. Though each gun was spaced about 30° in the horizontal plane, guns 1 and 3 were at the same height off the floor as the teddy bear but gun 2 was in the middle on the floor pointing up at the teddy's nose.

I need to explore further. Thanks for responding.

Holy smokes, you guys are way over my head. All I do... is set ISO as low as possible (noise averse) and shoot at F11 (DOF freak). Outdoors. I'm hopeless! Good work all around on your part (David & Dak).

 

[1971_M5]

You guys are nuts. In a good way! VERY interesting thread. Actually, I do understand what you're talking about... it's just that I'm not as dedicated to the craft you are... and my MO is pretty much... just point and shoot. Well, a little more than that. But not much.

 

[Dak on cam]

You guys are nuts. In a good way! VERY interesting thread. Actually, I do understand what you're talking about... it's just that I'm not as dedicated to the craft you are... and my MO is pretty much... just point and shoot. Well, a little more than that. But not much.

Well, that's the idea behind Nikon's CLS: you give it lights to work with and it uses them to improve the photographs without bothering you wth the details.

While I am fond of old flashes that work just in Auto or Manual, there are things where Auto is actually pretty bad. One example is shooting through an opening (like a door or window). The camera will only see the scene beyond the opening but the flash will quash based on the light reflected from the surrounding frame.

If you are shooting from inside with a tele in order to see how far a flash will reach, that can be pretty annoying.