Exposing for background when using OCF-TTL vs manual

[jadelm31]

Obviously there are many techniques to OCF and many various desired effects but when using an OC speedlight meant to add fill light to subject, properly expose background and subject with triggers, would this be correct? I would spot meter off of background in order to expose correctly for that and then lock exposure on camera, then use desired amount of flash to expose for subject. I know I can do this manually but if I were to shoot in TTL, how would my flash know to expose/fill and flash amount correctly for my subject rather than the whole scene since my camera settings locked in exposure for background? Is it even possible to use TTL in this setting? On the actual speedlight are the 3 various controls for backlighting, etc...etc, so I'm assuming I could just choose which one of those effects I was trying to obtain. Is this right?

Thanks!

 

[Derrel]

I'm guessing you typed this ? out on your phone. It's a bit unclear as to what you are actually trying to ask/communicate.

A few thoughts: SPOT metering can lead to wildly divergent meter readings, and I would use center-weighted metering and a test exposure or two to determine the "right" exposure for the background, and how you want to render it. If the background is bright tones, like sky-tones, do NOT over-expose it and blow it out! Spot metering can vary HUGELY,depending on exactly what is being read. FIGURE OUT the RIGHT background exposure uisng some method. Center-weighted averaging off of green grass is a decent "average" starting point.

Again, not sure what you want to know. ALso, COLOR-AWARE camera, like Nikons, and some of the very newest, high-end Canons, have "scene recongition software" and or/eye/face detection/and can also measure RGB values when the USER selects a target with the 4-way controller and the AF system, so the TTL is pretty intelligent, and it measures reflectance, distance, and also analyzes RGB values, so MOST of the time, modern, Nikon TTL is very,very smart. Color-blind cameras can sometimes put a LOT of influence on the AF area square that is selected and in-use.

What camera/what speedlight/what speedlight flash mode, TTL or TTL-BL (BL means Balanced Lighting) makes some difference. OLD Canon? New Canon? Nikon with SRS and 3-D RGB Color Matrix Metering?

ANswers to questions WRT TTL flash operation depend a lot on the actual flash and camera being used, as well as the metering or AF mode. Before Scene Recognition and stuff, the FOCUSING SQUARE in use was a huge influencer of the flash exposure for example with Canon cameras. Same thing with the flash unit: Canon's 580 EX was very erratic and VERY focus-spot dependent; the 580 EX-II uses the ALL-NEW EX-II TTL protocol, much better consistency. Nikon's older D-TTL control was very erratic and all over the damned map...so, the ACTUAL FLASH UNIT and the camera can one, or both, control how things turn out, and affect how you use them.

Your questions are, again, unclear. But one tip: FLASH can be controlled multiple ways. Manual using fractional power; AUTO-aperture with the camera in Manual metering mode; TTL; TTL BL, the two TTL modes with + or Minus exposure compensation; Programmed flash with Exposure Comp. There are actually two exposures most of the time outdoors: the AMBIENT light exposure, and the flash part of the exposure. During the day light hours, ambient is very strong; at twilight, it's less of a strong part of the exposure.

 

[jadelm31]

LOL, yes totally typed from my phone while also holding a baby

Let's try again. Thank you BTW. My question has to do with the mechanics of the speedlight and (sb 700) how TTL determines the right exposure or rather, flash output. Let's say my speedlight is off camera and it is mid-day. I want to expose in camera for my ambient light and background and use the flash as fill for my subject so I adjust accordingly. Now, my SB700 is set to TTL and is positioned off camera, how and what does my flash interpret the scene and how much output to expose for? When I adjust my Nikon D7000 to expose for say, the ambient light, can TTL still be used to properly add the right amount of fill light to my subject or in this situation, or can I only manually adjust my flash to achieve proper fill?

In other words, what settings would you do in camera and on flash to accomplish this? I usually shoot aperture priority and in this circumstance, wanting to properly expose for background and not blow out the sky (mid-day problems)...I might spot meter off the sky or use matrix. That would take care of my camera settings...now for the flash??

 

[jadelm31]

I am having a hard time communicating this question still. Hopefully this is a bit more clear.

 

[jadelm31]

How does the TTL metering off camera work? LOL..maybe that is what I'm asking.

 

[Tee]

What are you using to trigger your SB 700?

 

[jadelm31]

I'm using a Phottix Strato TTL transmitter/receiver

 

[gsgary]

I would just shoot them manual then i know it's going to be right, you do know there are 2 exposure when shooting ambient and flash, aperture controls flash and shutter speed controls ambient

 

[jadelm31]

Right, so if I want to underexpose my ambient I am going to choose a faster shutter and if I want a higher flash output, then aperture more wide open? Right? If aperture controls flash and shutter speed controls ambient then I also can't be adjusting for DOF without affecting the flash? This is where I get confused.........I want to be able to control my dof and my shutter speeds but also control the amount of ambient light and flash which seems to both be directed by the same controls. No?

 

[jadelm31]

I'm shooting an event where I will be moving around a lot and having to readjust quickly and often which is why I was contemplating using the TTL.

 

[jadelm31]

bump

 

[TreeofLifeStairs]

I know with my speedlight (Metz) even when I shoot TTL I can choose how many EV it exposes. The lower the EV the more ambient light will be in the scene. The higher the EV the more light will be on the subject but less ambient light will be in the scene. Is that what you're asking about?

 

[bratkinson]

While a professional photographer will recognize unusual lighting situations and more or less automatically handle it, amateur that I am, -IF- I recognize the unusual situations, I'll simply take a shot, look at the results on the LCD, adjust, and try again. If needed, I'll take several shots to figure out what I need and then, use those settings to get the shot(s) I want.

Plan B is the tried and true method from the film days...bracketing. Take multiple shots progressively adjusting 1 of the exposure triangle elements from lowest reasonable to highest reasonable levels. For night shots with slow film in the hills of Los Angeles, I took perhaps 6-8 shots changing shutter speeds from 2 seconds to perhaps 30 seconds and then picked the winner after I got the slides back from the lab. These days, with the capabilities of post processing programs, one can easily fix slightly under- over-exposed areas and if needed, even combine multiple images to get the best of both as the 'final answer'.

In short, don't fret about having all the numbers/settings/flash options for a particular situation all 'in your head'. Let the camera do most of the work and take several bracketed exposure shots as 'protection' and decide what to do while post processing. For what it's worth, I oftentimes set the camera in Auto and take a shot, then switch to Av/Tv/M as desired and make adjustments based on what the camera had decided in auto. It saves a lot of up-front head scratching.

 

[cynicaster]

A lot of variables to consider, but OP, as a general statement, modern TTL flash metering systems are capable of identifying what is intended to be the "subject" of the shot, and thus are able to expose that subject separately from the background. The gist of how the system works is this: the camera fires a quick "pre-flash", then compares the exposure it gets from that flash with the exposure it gets without the flash. It identifies the area of the frame that receives a boost in exposure from the flash, deduces that to be the intended subject that needs to be exposed "correctly", and sets flash output accordingly for the "final" picture. The system is actually a fair bit more fancy than that, but that's the general idea.

So, you can set your ambient (background) exposure in Av mode to your liking, point the camera at the subject(s) and shoot. The background will be exposed according to your Av settings, and the TTL system will attempt to expose the subjects correctly. At that point, you can tweak either the background or the subject exposure with exposure compensation or flash exposure compensation, respectively (I trust you know what those functions do).

Personally, this all sounds like too much of a headache to me. I'd probably just set everything manually and go by trial and error. Once I get it right, it will stay right until the conditions change significantly.

Right, so if I want to underexpose my ambient I am going to choose a faster shutter and if I want a higher flash output, then aperture more wide open? Right? If aperture controls flash and shutter speed controls ambient then I also can't be adjusting for DOF without affecting the flash? This is where I get confused.........I want to be able to control my dof and my shutter speeds but also control the amount of ambient light and flash which seems to both be directed by the same controls. No?

First of all, the aperture affects both the ambient and the flash exposure. Same with ISO. The shutter speed affects ambient, yes.

This is why manual is a good idea. Set the aperture to achieve the DOF you want. Use the shutter speed to get the background exposed the way you want**. Once these are set, you can concentrate strictly on getting the flash exposure correct--either by manual setting or using TTL.

** note, if it's broad daylight outside, you're going to have a hard time getting shallow DoF without massively overexposing everything, because your shutter speed is limited to ~1/200s when flash is used. Solutions to that dilemma include use of ND filters and/or flashes that provide high speed sync capabilities.

 

[jadelm31]

Thank you guys so much! You completely answered my question. I have a high-speed sync flash; the SB700 and can shoot at high shutter speeds with that, but if I recall, full power of the flash cannot be used passed a specific shutter speed- it will fire, but not full power. As for the broad daylight, sun over head, awful lighting situation. I think I will expose as best I can for the background, control my DOF and hopefully shoot as open as I can, and use my flash to fill the shadows from the subject/subjects.