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SB800 Problem: Unbalanced light output between Master and slave

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eManu

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Hi,

I need some help regarding the flash Nikon SB800. I have two of them and I can't get them working properly together in TTL mode (well I am pretty sure they are fine and that the problem is me :-). Here is the setup:
  • One SB800 as the Master unit connected to the camera (D70) with a SC-28 cord
  • One SB800 as the slave/remote unit
  • Both in TTL mode
  • Camera Flash Mode set to TTL.
The result and my problem, as seen in the test picture below (look at the shadow), is that the Master flash output is more powerful than the remote unit (and yes both units have freshly recharged batteries). So, is it a normal behavior or am I missing something?



I did another test with both flash units set to AA mode and the result seems correct: Both unit have the same output as seen below:



And, no, I am not asking for critics about these two wonderful pics ! :-) But rather what am I doing wrong (or not doing) that the light output is unbalanced when using the TTL mode.

In advance, thank you for your help.

Best Regards,

--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
Hi Manu,

I am using the SB800 as master en the SB600 as slave. This is my experience until now (and I am at the starting point of the learning curve!!).

If you are using a master and slave, you set one SB800 as master. You can see in the screen on the back of your SB800:

M -1.0
A 0.0
B --
C --

This means that in TTL the master is set to compensation -1.0 and the flashes in group A are set to no compensation. With select you can go from one group to another.

In the first picture you see that one flash is outputting more light (1 shadow). In your second picture you see two shadows. To eliminate shadows you have to move the flashes up so that the shadows become smaller en 'hide' behind the 'model'.

Or you need to use device to diffuse the light more light an umbrella or softbox.

What works for me when shooting portraits (just found out yesterday):
SB800 on hotshoe of camera set to compensation between -1.0 and -2.0.

SB600 shooting in umbrella (white inside/black outside to minimize light loss), more on the side of the face of model.

Almost no shadow on the wall, see my progress on treat:
http://forums.dpreview.com/forums/read.asp?forum=1025&message=17006911

Good luck,
Marcello
 
Kent Johnson said:
Why do you need TTL?
-Kent
Click to expand...
Good question, why do I need what seems to be a great feature, available with my combo SB800/D70?! :-)

While I got my flashes some time ago I am just beginning to learn how to use them and I assumed (may be wrongly) that the TTL mode would be a good starting point.

Now TTL may be not a good choice, however I am still curious and woud like to know why the light output is unbalanced.

--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
JaydonArcher,

Thank you very much for the link. I didn't have time to read it completely yet but it seems full of very useful information.

About the model position, your point is taken. However at that time I wasn't actually trying to get ride of the shadows but just testing the light output.

Best regards,
JaydonArcher said:
Try this
http://www.daveblackphotography.com/workshop/0408.htm
And consider moving the model farther from the background.
--
I wish I had something clever to say.
Click to expand...
--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
Marcello,

Thank you very much for the information. I will give a try since I also definitely need to learn the in and out of flash operations. However, Like I said to JaydonArcher, in my tests I wasn't even trying to get ride of the shadows but just testing the light output and still don't know why the light output is unbalanced in TTL mode.

About finding a willing model (as stated in your other post), I gave up a long time ago and it is why I bought that wooden model ! :-)

Best Regards
Marcello Geerts said:
Hi Manu,

I am using the SB800 as master en the SB600 as slave. This is my
experience until now (and I am at the starting point of the
learning curve!!).

If you are using a master and slave, you set one SB800 as master.
You can see in the screen on the back of your SB800:

M -1.0
A 0.0
B --
C --

This means that in TTL the master is set to compensation -1.0 and
the flashes in group A are set to no compensation. With select you
can go from one group to another.

In the first picture you see that one flash is outputting more
light (1 shadow). In your second picture you see two shadows. To
eliminate shadows you have to move the flashes up so that the
shadows become smaller en 'hide' behind the 'model'.

Or you need to use device to diffuse the light more light an
umbrella or softbox.

What works for me when shooting portraits (just found out yesterday):
SB800 on hotshoe of camera set to compensation between -1.0 and -2.0.

SB600 shooting in umbrella (white inside/black outside to minimize
light loss), more on the side of the face of model.

Almost no shadow on the wall, see my progress on treat:
http://forums.dpreview.com/forums/read.asp?forum=1025&message=17006911

Good luck,
Marcello
Click to expand...
--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
I can't figure out why the CLS system does certain things, and I wish it were better documented. Even the person everyone refers to for CLS expertise, Dave Black, sounds like he doesn't expect them to perform predictably. From his August 2005 tutorial: "I started with both A and B groups of SB800s at a power output of 0.0 and "take a shot, take a look." I will power up or down according to how I want the light to look. This is how I set power outputs on the SB800s for any situation. "

In your sample image, it seems to me that the CLS system is evaluating both flashes simultaneously, rather than individually. For some reason, perhaps latency, the master light "gets there first" so the 2nd light is not being told to fire as long.

If there's one thing predictable about my SB-800s: they underexpose in wireless TTL. I'll keep testing, but I'm not getting any happier with them. Sure, they allow individual control, but they're not delivering in TTL for me.

Chris
eManu said:
I need some help regarding the flash Nikon SB800. I have two of
them and I can't get them working properly together in TTL mode
(well I am pretty sure they are fine and that the problem is me
Click to expand...
 
Sorry, I misunderstood about the shadows. I thought you were trying to rid yourself of the shadows but now I understand what you are saying. I use the SB800 and the SB600 slave. I have had trouble with the 600 going nuts and firing at full strength for no reason and blowing the shot.
When the 600 gets too strong I just turn it down from the 800.

Have you noticed that with the diffuser on the 800 the slaves don't worth that hot? My 600 won't even see it even when its close.
Good luck. Read that article in my other post. I learned a lot.
--
I wish I had something clever to say.
 
and its not TTL vs other mode. You're first picture shows the Commander stobe pointed up and away from the subject. Only the right side slave is pointed at the subject. The second image is correct because the two strobes are both pointed at the subject.
--
Ken Eis
 
Ken, the strobes look in exactly the same position in both shots. And the right strobe is the Master, not slave, as you can tell from the cord. And in TTL the direction of strobe head should does matter, only the light hitting the subject. Your assessment might be valid if strobes were firing at full power and out of range, but at 1ft it makes no difference. The CLS system is failing in this situation, and it's not obvious from the photo why that is the case.

Chris
KenEis said:
and its not TTL vs other mode. You're first picture shows the
Commander stobe pointed up and away from the subject. Only the
right side slave is pointed at the subject. The second image is
correct because the two strobes are both pointed at the subject.
--
Ken Eis
Click to expand...
 
Manu, did You check the Mastrer's zooming head and the Remote's one are set at the same focal-length?
Due to the diffusers, that should get almost no rilevance, though.
Anton
 
First, thanks to Chris3010, KenEis and Augusta for your reply:
  • Chris3010: Right, both flashes are almost at the same position and the right one is the master.
  • KenEis: Nice try but wrong (see above) :-)
  • Augusta: Good idea about the zooming head (see remarks below).
In my original post I forget to mention that the built-in wide-flash adapter and the diffuser dome were on. And when doing so, the head zooms automatically to 14mm. So I did a set of test as shown below:



Do these test shots are of any interest? I so, can you draw any conclusion? Personally, I am still in the dark (pun intended) :-)

Shooting data (same for all pics):
Nikon D70
JPEG (8-bit) Basic
Image Size: Large (2000 x 3008)
Lens: 18-70mm F/3.5-4.5 G
Focal Length: 18mm
Exposure Mode: Aperture Priority
Metering Mode: Multi-Pattern
1/60 sec - F/8
Exposure Comp.: 0 EV
Sensitivity: ISO 200
Optimize Image: Custom
White Balance: Flash
AF Mode: AF-S
Flash Sync Mode: Front Curtain
Auto Flash Mode: Balanced i-TTL
Auto Flash Comp: 0 EV
Color Mode: Mode IIIa (sRGB)
Tone Comp.: Normal
Hue Adjustment: 0°
Saturation: Normal
Sharpening: Medium high
Long Exposure NR: Off

Best Regards,

--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
I have Canon rather than Nikon gear but I suspect your problem is due to the fact the flash heads are in the photo. That will screw-up TTL exposure big time. Try moving the flashes out the of the photo and see what happens. The other issue might be a lack of good line of sight communication between the camera and flashes if that is required for CLS.

I came across this site with Google which appears to be a very comprehensive tutorial for the SB-800.

http://www.mir.com.my/rb/photography/hardwares/classics/NikonF5/Flash/SB800/index.htm

On page 4 in the section on wireless it specifically warns against letting light from remote slaves enter the lens directly: "Take care not to let light from the remote flash unit enter the camera lens directly or indirectly in TTL auto flash mode.... Otherwise, the correct exposure cannot be obtained."

CG

--

Feel it - Shoot it - Understand it: Shoot with feeling always, then ask, 'How did I do that? How can I make it better?'. See: http://super.nova.org/DPR
 
Thank you very much Chuck, I did a set of tests without the flahes in the frame and it is now good. I knew it that the problem was the photographer!

Thank you all.

Best Regards,

--
Manu
FCAS Member #118 (DSLR division)
PAS Member
 
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