Unerexposed when using Phototix Odin triggers and SB-600

LilyJack

Okay. So trying out off camera flash. Just trying basic set up to get an traveling, indoor studio lights for things like headshots. I've bounced flash before, used a beauty dish a couple times and could figure it out but not an expert on strobes but I understand some basic stuff. Although this is making me wonder...

I was finding this when while using the SB-600 to set up for something else last week and finding it happening again with Phototix Odin triggers with Phototix Flash (new toys today so just getting familiar with them). So here goes:

Using D300. Flash set up within 2-3 feet of subject, using my 50mm, ISO 400 (although I know I want 200), speed at 1000 (doesn't matter in regards to flash but does with ambient which I don't want any of and I have high speed sync set), f3.2 (and had down to 2.0), High speed sync set and it doesn't render bright. Batteries are fully charged. In the first instance, I was using a white background and so I assume the histogram should be heavy on the right, showing blown highlights. It's not. Using TTL so is it trying to meter to gray?...OK tried this with new Phototix system. In this instance, it's not a white background but a midtone piece of fabric. Still, histogram is heavy on the left and when I bring it into PS, the images are totally underexposed. I've checked to make sure exposure compensations and flash compensations aren't set. It just seems wrong that I’m not completely blowing out highlights (the entire white background) at the above settings. Histogram is all the way on the left and barely hitting the middle. To get correct histogram/exposure, I have to turn compensation up to +3.

So, speed doesn't effect flash but just for S&Giggles, I change the shutter speed. Things are looking better and it's not the ambient light. I swear because the white balance looks is, well, balanced for flash.
I then set the Odin transmitter to M instead of TTL and bring it to 1/1. Looks even better but still not getting any pure whites so it's slightly underexposed. Shouldn't TTL work?

Does that feel right to you? How am I not blowing subject way out? I feel there's got to be a setting wrong on camera but I can't figure it out. I'll be really embarrassed if it's something simple but gotta ask at this point.

Thanks for your help,
Take care, Kate

ziggy53

Your camera's automatic metering (assuming the "Matrix"* metering mode for Nikon) system is designed to produce a scene without any blown or pure whites. If there are any specular highlights this will be accentuated (the white background will be darker still).

In fact, if you only had a white background and nothing else in the scene for the camera to sense, the scene would be a medium gray/grey. Why? Because that is the way the system is designed to operate, to expose a scene for medium gray/grey by default (but with additional automation to prevent overblown highlights beyond a certain percentage in Matrix metering mode). The system cannot know what is designed to be pure white unless you tell it by overriding the system (in an automated mode) with a plus EV/FEV value, or, in manual mode with the background exposed for white by watching your histogram** and the highlight "blinkies" in the LCD display, which should be turned on.

I suggest using only manual mode in a static scene situation, like a studio setup. Then you need to meter the background and subject separately, if you want a truly white background and a properly exposed subject. You will probably find that the white background needs more light dedicated to the background, because light diminishes as distance increases, and the subject will be closer to the lights in many/most simple lighting setups.

---

*Please advise what metering mode you are using.
**The histogram is not absolutely accurate, however, and you also need to do some testing in order to understand what the histogram represents in different scenarios. Each camera model varies somewhat in this regard.

Generally, you are better off with the histogram set to RGB mode so that you can see individual color channels and what for a color channel overexposure (when color tonal values need to be accurate).

LilyJack

Hi Ziggy! Thanks. I always use my camera in manual mode so I'm not autoexposing anything (therefore not allowing camera to meter to gray). Ap is nearly wide open..Meter mode is Center-weight.

But, does the TTL do that?

Hackbone

Your flash is two feet away from your subject. I'm assuming your subject is 4 feet from the big. Let's say you meter says f 8 for your subject however you do not have f8 on your bkg. The bkg would be around 5.6, not as bright as your subject as the light is traveling twice as far hence the light intensity falloff. The bkg would not be white as a result. Generally your bkg to be white should have about a stop more than your subject.

If in a fixed position I would always have the strobes on manual. Soooo much easier.

ziggy53

LilyJack wrote: »

Hi Ziggy! Thanks. I always use my camera in manual mode so I'm not autoexposing anything (therefore not allowing camera to meter to gray). Ap is nearly wide open..Meter mode is Center-weight.

But, does the TTL do that?

To answer your question, "... does the TTL do that?"; yes, the flash automation is still in play, and the camera's flash meter is setting the flash component of the exposure automatically (by throttling the flash output). Good that you used HSS mode to quench the ambient light.

Be sure that you really are at a distance of 2-3 ft. If so, the SB-600 flash should easily do that distance at ISO 400 and f3.2, even with HSS mode, although you may not get much light spread at that distance unless you use the wide-flash adapter and widest zoom setting, which will dramatically cut light output in HSS mode.

I suggest contacting Phottix USA at info@phottixus.com to see if they have any ideas. (They will probably suggest a number of things to check.)