TTL VS MANUAL explained - off camera flash

[sam_clay]

<p>Hiya<br>

wondering if someone can help me out.<br>

I have just started to take my SB700 flash off the camera and sit it in a soft box to take portraits to the next level.<br>

I understand that TTL is through the camera, and because i like to work quickly, and i understand TTL is pretty good, I want to explore this avenue further.<br>

I have the pocket wizard set up and the AC3 for compensation ease etc.<br>

i watched several YOUTUBE videos of this guy called Rick Salmon who is quite the master at TTL flash amongst other things, but he never quite explains it fully. Flash on TTL, Camera on manual.<br>

He says to expose for the background and then shoot away. However, how close should the soft box be from the model ? and at what distance can i use my 70-200 VR11 for example ? I am supposing that if i expose for either the model or background standing at the same distance as the soft box, that I could then stand at ANY distance to take the shot because the flash would be the main source of light ?<br>

I apologise if I am getting this all wrong. I would really like someone to explain a little to me about this if possible. Its easy to compensate the flash with the AC3, but i still am unaware about distance of soft box and camera and why ?<br>

any help much appreciated. Practice makes perfect I know, but if there is a bit more info from anyone then that would be great. WhEn on TTL the flash tells me something like 4.8 ft - 5ft for example ? is this the distance the soft box should be ?<br>

I also understand that a fast shutter at 250th and 8 f stop for example should kill the ambient light and light the model to stand out.....<br>

I could be wrong and any further information would be a great help. I apologise if i am getting this all wrong, but I am finding it hard to get my head around.<br>

thank you</p>

<p> </p>

[Jochen_S]

<p>Sorry I neither ever used pocket wizard nor Nikon TTL, so I can't tell if that wireless stuff substitutes a Nikon cord between flash & camera. - About exposure: there is a guide number for the flash somewhere. - The softbox might eat 2 fstops so take half of the guidenumber (for your ISO of choice) divide it by fstop and you get the maximum flash - model distance. Guidenumber math is meant to avoid underexposure, TTL is for avoiding overexposure within the guidenumber stuff's upper limit.<br>

Camera model distance doesn't matter - shoot that 200- 400 with converter if you like...<br>

Softbox model distance should be no more than 1.5x softbox diameter for a really soft light.</p>

[William Michael]

<blockquote>

<p>. . .Flash on TTL, Camera on manual. He says to expose for the background and then shoot away.</p>

</blockquote>

<p>I haven’t watched the youtube video, but I am <strong><em>guessing</em></strong> that the instructor is suggesting that you set the AMBIENT EXPOSURE for the background.</p>

<p><strong><em>If my guess is correct</em></strong> then, you probably need to grasp the concept that there are TWO exposures: one is the AMBIENT EXPOSURE and the other is the FLASH EXPOSURE.</p>

<p>The instructor suggested setting the camera to MANUAL so that you will make the exposure for the background as the AMBIENT exposure and you will do this manually using the camera’s TTL meter.</p>

<p>So you will meter the background and set the camera’s exposure manually as if there is NO flash being used: obviously you will choose a shutter speed within the Flash Sync Range of the Camera and you will also choose a suitable Aperture for an adequate DoF that you require for the shot and thus you will have a resultant ISO that will sort of be selected based upon Shutter Speed and Aperture that you have chosen.</p>

<p>Then you will place the model in front of the background and set up the OFF CMAERA FLASH.</p>

<p>***</p>

<blockquote>

<p>However, how close should the soft box be from the model?</p>

</blockquote>

<p>In regard to the exposure, it doesn’t matter provided that you are closer than the MAXIMUM WORKING DISTANCE of the flash. This is because you have set the FLASH EXPOSURE to “TTL” that is to say the flash exposure will be managed automatically by the TTL metering system of your camera and flash unit.</p>

<p>But you will choose a distance that is both comfortable for the Subject and give s the LIGHTING EFFECT that you require. These finer points are best achieved by experimentation and trial and error. Really there is no substitute for experience and digital negatives are very inexpensive to process.</p>

<p>Guide numbers could be used to work out mathematically the maximum distance that you can work the Flash, Off Camera – BUT - because you are using a soft box as a light modifier then the Soft Box will attenuate the light from the Flash and therefore the mathematical computation will be complex: but as suggetsed above, it is reasonable to assume that the Soft Box will attenuate the Flash about two stops - so that is a good starting point. However, I'd suggest it would be easier, <strong><em>moreover it would be</em> <em>a better learning experience for you </em></strong> to work out by trial and error how far away the soft box can be placed without getting the FLASH underexposed.<br>

<br /> ***</p>

<blockquote>

<p>. . . and at what distance can i use my 70-200 VR11 for example ? I am supposing that if i expose for either the model or background standing at the same distance as the soft box, that I could then stand at ANY distance to take the shot because the flash would be the main source of light?</p>

</blockquote>

<p>Yes you are correct. As the Flash is OFF CAMERA it doesn’t matter one iota how far away you set the camera from the Subject, because the flash will still make the same amount of illumination on the Subject – because it is OFF CAMERA.</p>

<p>Yes you are correct. In this lighting scenario, the FLASH is usually the KEY LIGHT (the main light). You can BALANCE the FLASH EXPOSURE relative to the AMBIENT EXPOSURE by using “FEC” (Flash Exposure Compensation).</p>

<p>WW</p>

[Palouse]

<p>Some good info here: http://www.scantips.com/lights/flashbasics.html<br>

<br />and also here: http://www.amazon.com/gp/product/1608952789/ref=as_li_qf_sp_asin_tl?ie=UTF8&tag=planeneilphot-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=1608952789</p>

<p> </p>

[ellis_vener_photography]

<I>"...how close should the soft box be from the model?"</I> <P>

 

Where the light is placed and how you shape it is determined by two things: primarily what you want the lighting on the

subject to look like. <P>

 

You haven't said what size soft-box you are using but a very general rule of thumb is that the ideal subject-to-softbox

distance is equal to the diagonal across the face of the softbox. With a light at a 30~45 degree angle to the face, this

produces a very nice three dimensional modeling effect. It also creates a nice fall off of brightness from the part of the

face that is closer to the softbox to the other edge of the face. The combination of these two effects is commonly referred

to as "wrap around."<P>

 

If the diffusing surface of the soft-box is approximately the same size or larger than he subject, moving the light closer to

the subject than the diagonal will make the light appear "softer" by lowering the overall contrast; Shadows will be smaller

and softer edged. Conversely, using a smaller softbox or moving the softbox further away will make shadows more

defined and the light will look "harder". Which will make for a better looking portrait? That depends on your intent and the

3 dimensional qualities of your subject. Do not forget that changing the angle the light is coming from will have a huge

effect on the quality of the lighting and a viewer's emotional perception of the subject. <P>

 

Secondarily, especially with hot shoe mount size flashes, you are limited in flash placement by the energy limits of the

light. An SB-700 isn't very powerful as flashes go although compared to constant lights like tungsten, quartz-halogen,

fluorescent, and LED lights it's very powerful. <P>

 

<I>"and at what distance can i use my 70-200 VR11 for example?"</I> <P>

 

As long as the lens can focus on the subject you can use the camera at at any distance to the subject.<P>

[ellis_vener_photography]

I use the PocketWizard ControlTL system with both the Nikon and Canon camera and flash systems, as well as with the

Paul C. Buff Einstein E640 monolights, and have for several years now. I've also used it with Elinchrom lights that have a

port for an external Skyport transceiver.

[dan_south]

<p>Flash units in TTL mode will try to deliver a correct exposure no matter what you do. However, there are limitations. For instance, if your soft box (or unmodified flash) is far from the subject, it might not have enough power to do what you need it to do. Likewise, if you are using a small aperture (e.g. f/11), that will require more flash power (multiple speed lights).</p>

<p>A flash photo has two exposure - the ambient light exposure and the flash exposure. If you expose correctly for ambient light and use TTL, the TTL will add fill flash for shadows. That's a good place to start.</p>

<p>Option 1 - Encourage the TTL to put more light on the subject with flash compensation of +1 or less light with flash compensation of a negative value (-1, -2).</p>

<p>Option 2 - Set the flash compensation back to 0 and under-expose the background by a stop or two. This darkens the background and highlights the subject.</p>

<p>Option 3 - Do all of the above with the flash in manual mode.</p>

<p>With some experimentation, you'll figure it out.</p>

[purplealien]

<p>I found Neil van Niekerk's "<a href="http://neilvn.com/tangents/balancing-flash-and-ambient-exposure/">Tangents</a>" blog really useful for learning how to balance flash with ambient light. He also has a series of books.</p>

<p>Chris</p>

 

[sam_clay]

Ah I see - really terrific answers! It appears I may have

over complicated things in my head as it actually seems

very straight forward x thanks so.much guys that really

really helps me!!