D70+SB800+Umbrella+iTTL = Underexposure

[kab]

Just bought an umbrella and started playing around with some portrait pix.

I've setup the sb800 wirelessly pointing into a silver reflective umbrella which is attached to a tripod via an adaptor. I've done some test shots and the flash seems to be filling most of the umbrella with an even light spread. The sb800 has the diffuser dome attached. I'm shooting in the D70's manual mode, handheld at ~ f8 1/60sec. The umbrella is setup camera right, fairly close to the person, with the umbrella stem more or less pointed towards the persons nose.

When setting up the d70/sb800 in commander/remote mode, most of my results look like they're underexposed by 2 or 3 stops.

A few questions:
1) Have you experienced similar results??
2) Should you even use CLS/iTTL when shooting into an umbrella if you're hoping for consistant results??
3) Should I be using the diffuser dome?? My tests when shooting into the umbrella to measure light spread seems to suggest yes.
4) How would you typically setup your sb800 and d70 when shooting into an umbrella?? Any pics of setup??

I also tried a few manual/su4 combinations, again with limited success (severely underexposed or overexposed).

[Mr Darcy]

I want to know the answer to this one too. I have just ordered my umbrella

Some things I have discovered though.Commander mode iTTL does have limitations. I was shooting bottles, and was having similar issues to you.
(I was also having issues with reflections, but that was my subject, you shouldn't have the same problem & besides you already have your umbrella

What I found to be the best was to use Commander mode Manual, with the camera on manual as well. I then played with the settings till I got properly exposed photos, then I wrote down the settings and left things alone. As you are controlling the light as well as the exposure, you should have no problems once you get it right once. (You may need to compensate for dark/light subject, but this will be minor tweaking)

Another thing I found very helpful was Camera ControlPro (Trial version available on the Nikon Website). This allowed me to make adjustments and take the photo direct from the PC, view it immediately on a big screen and adjust instantly.

Since you are using a live model, it may be a good idea to substitute a still life till you get the exposure about right. Otherwise your model willl be complaining about the excessive flash use before you get your good results.

[Oz_Beachside]

The camera, in any TTL, can only make decisions based on the information available to it. It "assumes" you are pointing the flash at the subject, but you are not.

The camera most likely does not know that you are bouncing off an umbrella. The umbrella will most likely reduce the effective power output of the light to the subject. So, if you are underexposed, you will need to increase the power of the lfash, by the amount that the umbrella "consumes". You can do this by increasing the EV compensation of the SB800. I have an SB600, so assuming its similar, you simply push up arrow, and you with see a +.05 etc increase. THe flash will pop brighter, and after some trial and error, you will work out how much your umbrella "consumes". Might be up to 2 stops, try it. Set your flash to +1. THen +1.5. Then +2.

If you have a meter, you can measure it, or use trial and error.

For mounting, I use the manfrotto umrella bracket with a hotshoe adapter. Think they call is a multi clamp. Or a super clamp.

have fun

[gstark]

Let's have a quick review of your setup. I've used a similar one on countless occassions with no issues.

First of all, I prefer to not use iTTL, but that should not be an issue here.

My first question is a very basic one: how have you mounted the flash in regards to the brolly?

Looking at the SB800, it has a front and a back; which of those sides - the front of the back - is actually facing the brolly?

It sounds to me as if you may have the front of the SB800 facing the brolly, but in this sort of setup, that is not correct. You need to swivel the 800's head through 180, so that the front of the flash faces your subject, and the back, and the actual flash head, is facing into the brolly.

That's a fairly basic error, but one that's easy to make if you're inexperienced.

Next cab off the rank is the lack of exposure, providing you have this setup correctly. What mode is the flash in? What mode is the camera in?

Also ensure that the flash is set for full power: if you've been messing with power settings, resetting them back to normal is insidiously easy to overlook, and damn difficult to isolate as your problem.

Let's not forget subject-to-flash distance, and the EV/aperture relationships that you will be establishing. Using a broly, you will be typically increasing the flash to subject distance by about a meter and a half, which will cause you some element of light falloff. Further, the diffusion effect of the brolly will also cause you to suffer light falloff, and the loss of two or three stops of light would not be surprising in this scenario.

So, armed with this information, that probably means that if you think you will be wanting to shoot at F/11, you may want to reconsider that position.

Let's see how you go with addressing these potential pitfalls as a starting point, and then we can see what we next need to consider.

[gstark]

For mounting, I use the manfrotto umrella bracket with a hotshoe adapter. Think they call is a multi clamp. Or a super clamp.

I think it's either a multi clamp, or a brolly adapter.

The super clamp is a different beastie altogether.

[kab]

Thanks for the prompt responses.

Gary, I think you are spot on. I've got the front of the SB800 facing the brolly. I haven't seen a brolly setup in the flesh, so it looks like I've made a classic Lighting 101 mistake

Oz, I didn't even consider playing with FEC on the SB800 instead of on the D70. From memory, the SB800 will allow me upto 3+ stops as opposed to only 1+ stops on the D70.

Looking forward to getting home and putting your suggestions into practice....

[gstark]

Gary, I think you are spot on. I've got the front of the SB800 facing the brolly. I haven't seen a brolly setup in the flesh, so it looks like I've made a classic Lighting 101 mistake

Keith,

That's why I made that one my first point.

Please don't feel embarrassed about it; it's an easy and understandable error to make, even though, once you think about it for a minute or three, you see that you need to slap yourself a couple of times for making such an obvious error.

I think that once you address this issue, you'll see a vast improvement on your exposures; while there will certainly be some light falloff from using the brollies and the extra distances the light needs to travel, I wouldn;t be too concerned about FEC at this juncture. With the front of the 800 facing the subject, you'll be getting much better metering and more light onto your subject, and all will be well.

Just pay attention then to my other point, and look at the apertures that you are using. Keep the issue of light falloff in mind, and be prepared to open up a stop or so if need be.

[beetleboy]

Gary's correct RE the direction your SB800 needs to be pointing for iTTL flash. I would suggest switching your flash to Manual and adjusting the power of the flash via the "Commander Mode" on your D70 since you're going to be shooting 'trial and error' style anyway. As long as your flash-to-subject distance remains the same you can fire away assured the exposure will remain the same.

Also, remember you can adjust the balance between ambient light and flash light using your aperture and shutter speed settings. Check out http://strobist.blogspot.com/ for all the in's and out's of off-camera flashing!

[kab]

Yep, turning the flash round certainly improved the exposure in iTTL mode, but as beetleboy mentions, it's still easy to get inconsistant results.

Thanks for the strobist link. I've been there a few times, and it's a wealth of information. I think I now get how iTTL works b/w the D70 & SB800, but I'm a little unsure of how the two interact in manual mode, which is what I'm exploring now.

More testing is required, but I've quickly tried the following with some consistant results:
- SB800 set to SU-4 manual mode, full power 1/1
- D70 in M mode for full control of Arperture and Shutter speed
- D70 flash mode set to Commander Mode --> Manual --> Full

With this setup, it seems that I can control the flash intensity via the D70's arpeture/iso/shutter speed controls. So when you say manual mode, is this basically what you're all doing??

[beetleboy]

Nope!

Via the menu system on your D70 (haven't used my D70 for a while so can't remember the order) you need to set the on-board flash to "Commander Mode". You then set your SB800 to "Remote" mode. This way the D70 is telling the SB800 what to do.

For more info, do a search on this forum for "SB800 + Commander Mode" or something similar and you should be able to find more specific info to help you out!

[Mr Darcy]

D70 Flash control: CommanderMode->Manual->Full(or whatever)
SB800: Remote (I like to turn the beep on too so I know it's fired OK)
D70: Manual exposure. Shutter=1/500 to minimise ambient light Slower to use it. Aperture as required. Start with F11 and experiment from there.
If you need to completely eliminate flash from it, cover the onboard flash with some old exposed but developed slide film or similar.

If you have the d70 in commander mode, and the flash in SU-4 mode, the 800 will fire with the preflash, and will not fire properly, if at all, when the shutter is open.

[MATT]

Kab, can you post some results please..


Cheers
MATT

[Alpha_7]

Kab, can you post some results please..
Cheers
MATT

With Exif attached if possible, would definitely help assess the situation more throughly.

[Oz_Beachside]

THese are great to hold the flash and the umbrella...

http://www.calumetphoto.com/item/BG4255.html

Add a hotshoe bracket, via an SC29, SC28, or if wireless the small metal thingos... "Hama Shoe Mount" http://www.vanbar.com.au/catalogue/index.php?id=134.144.79.41170814810&user=

[Greg B]

Just an aside as a matter of interest - I used the SC-29 with the SB-800 pointing into an umbrella and the exposure was spot on. Not sure what the specific differences are between this and Commander mode.

[Oz_Beachside]

Just an aside as a matter of interest - I used the SC-29 with the SB-800 pointing into an umbrella and the exposure was spot on. Not sure what the specific differences are between this and Commander mode.

Did the SC29 have the senson on the camera hotshoe?

[MATT]

Just an aside as a matter of interest - I used the SC-29 with the SB-800 pointing into an umbrella and the exposure was spot on. Not sure what the specific differences are between this and Commander mode.

Did the SC29 have the senson on the camera hotshoe?

Thats was what I was thinking..

MATT

[Greg B]

The thingy on the SC29 hotshoe is the same as the red thingy on front of the SB800 - it is an AF assist. The exposure is all taken care of by the camera.

I just wonder whether the cable connection of the SC29 somehow works differently to the wireless connection. The camera effectively decides the duration of the flash to determine exposure, so there is a message back from the camera to the SB800.

We really need that new Tom Hogan flash book - come on Tom, get it done!!

[kab]

I hear you Greg. A new Thom Hogan flash book would certainly go down well. Ok, so I did some quick & nasty tests yesterday to help illustrate my misunderstandings. In all cases the SB800 was set to full power

Below is my very basic setup:



First pic is done in iTTL mode. Still seems underexposed, but otherwise as expected:



Second pic is done with the D70's flash mode set to manual and the SB800 set to SU-4/Manual. Results are overexposed probably due to the fact that the internal flash was contributing to the exposure. This I can understand



This last image is the one I don't get. The D70 flash mode is set to commander-->manual, the SB800 set to SU-4-->manual, yet the exposure is severely underexposed. I can't understand in this case why the SB800 is not outputting FULL power??



A few more questions:
1) Am I expecting too much from the brolly & sb800?? With the SB800 set to full power shooting into the umbrella would there ever be enough power/light to overexpose an image (and then tone it down to obtain a correct exposure)
2) Can you actually use FEC on the SB800 when it's set to remote mode??
3) I presume FEC is useless if the flash is manually set to full power??
4) Do you usually use the internal flash to contribute to the exposure??
5) Does the brolly/flash setup look OK??

Dazed & Confuzed....

[xorl]

3) Should I be using the diffuser dome?? My tests when shooting into the umbrella to measure light spread seems to suggest yes.

The diffuser is really only required to simulate a bare bulb. In general there is little reason to use it with an umbrella since there is too much spill. Play with the zoom on the flash and the modelling light to find a suitable setting. If you have a wall just behind the umbrella it will be fairly easy to see how much light is being wasted.

[Alex]

I think part of the problem with the last image at least is that you choose SU-4 mode. I used it before and the pre-flash from your on board flash stuffs things up. Why not just use SB800 in remote mode?

Alex

[Mr Darcy]

SU-4 is a dumb remote mode. It fires when it sees a flash. any flash.
When the D70 is in manual mode (Flash) this os OK as it sees the onboard and goes off near as dammit to the same time. You get the output of BOTH flashes in the exposure. (Photo #2)

If you use D70 in Commander mode, and Flash in SU4 mode, what happens is that the Camera assumes that a remote flash is providing the light. It fires a stream of pulses from the Onboard to say "Ready... Set... GO". It doesn't provide much if any light to the subject. The FLash being in dumb SU4 mode sees the "Ready..." part of the signal and says "I see the light ...GO"
It fires on the first preflash. Then after all the flashes fire, the camera thinks: "The remote should be firing about now. I'll open the shutter". It does, but all the flashes have already fired, so the result is a badly underexposed photo (#3)

If you you set the camera to Commander mode, you MUST set the flash to Remote mode if you want it to work.
That way the Flash sees the preflashes and thinks. The camera wants 100% flash from Group 3A. Hey that's me. I better to be ready to fire when I get the Go signal. Wait for it Wait for it NOW!
Result is Minimal exposure from the onboard. Full light from SB800. Correct exposure (If you had the aperture set right)

[kab]

Thanks guys. Think I get it now... pretty simple really. Preflash forces SB800 to go off before shutter opens.

Will try a few more shots without diffuser dome to see if I get a good spread & more power.

Getting there....

[Cath4]

is there aproblem buying nikon products from china , i want the sc 29 for my sb800 and its painfull to pay fo in the uk £60
every thing i buy somethin i need some thing else, i never realised that i cant use my sb800 with ttl once off the cam without buing another flash unit,
so in order to use my broll set up , my make shift studio, im buying the sc29 , is there not an equivalent that doesnt have the coil thing , im going to need the lentgh,
some one here said they have used it with the brolly , do you have pics of it , didnt you get tangled!!

apart from that im skint just now , iv figuired using the creative so called high key white backdrop photos , manual 60th sec at f11 ..
they do have to all be the same , does fast food potraiture have to be to detailed? txt back cheers

[Cath4]

allso with my pop up flash , some toilet roll around it, so that it doesnt bleach out, but enough to set of sb800, am i being creative?
learning about lighting here.

[Cath4]

me again, i have a nikon d50

[DJT]

cath4, since you have the D50 you will need the SC29 to fire the flash off your camera or a radio transmitter.
Not sure about your location but dd photographics have the cord for $95.

[Cath4]

thankyou i will check that out , im in london though and off on holl at the wknd so looks like ill be paying full price rather than wait for post.