Flash Exposure Compensation quick+dirty- (and full blast)

<p>Hello, and wishing all a terrific holiday and wonderful start to the new year-</p>

<p>I get terrific, but sometimes unexpected, results using FEC. I'm grateful for ideas and pointers that will help fill the gaps in my understanding and help me get more expected results.</p>

<p><strong>The gear:</strong> a Canon EOS 5Dm1; a <a href="http://www.metz.de/en/photo-electronics/mecablitz-models/system-flash-units/mecablitz-36-af-4-digital/product-information.html">Metz 36 AF-4C</a>. The flash is a good value for the price and is good to learn on. But it, of course, doesn't hold a candle (yeah, yeah) to Canon's 580ex or 430ex. (Hoping to leave the "Why Metz?" part of the discussion here. It's a live and learn thing.) I shoot the Metz with a <a href="http://www.lumiquest.com/images/New%20Product%20Images/softbox.jpg">Lumiquest Softbox</a>, which is also terrific. The flash is ettl compatible when hotshoe'd. It fires full-blast when radio-controlled.</p>

<p><strong>My habit:</strong> I expose for ambient light, but purposely underexpose, wanting a day-for-night feel. The flash is typically a meter from the sitter, and off camera-left or above it. I dial the camera's FEC down a full stop from midpoint and experiment from there. I seldom change exposure settings, unless firing the flash remotely, in which case I control the flash's impact by stopping down. I welcome gloves-off corrections to this.</p>

<p><strong>What I'm after</strong>: just enough light on the subject so s/he pops, a bit, from the bg. Nothing overly dramatic or Kodak.</p>

<p><strong>It's the "experimenting from there" part that I want to fix</strong>. Shooting in the street as I do, there's seldom a second chance. It's rather unlikely that I can consult the screen or histogram, then recreate the moment. I guess what I'm after: some kind of ratio or formula from which I can build: My guide number is 36 meters, my distance is 3, my aperture is f/8. I should dial my FEC plus or minus 1/n.</p>

<p>Again, apologies for the clumsy wording. I'm nearly new.</p>

<p>As background and context for those with similar questions, these articles have be a wonderful help:</p>

<p><a href="http://photonotes.org/articles/eos-flash/">EOS Flash from Photonotes.org</a><br /> <a href="http://www.eosdoc.com/manuals/flash/fakeFEC/#t3">Faking Flash Exposure Compensation @ the EOS Documentation Project</a><br /> <a href="../photography-lighting-equipment-techniques-forum/00WbZk">Some of the discussion in this photo.net thread</a> (Fill Flash ratio and FEC)<br /> And, of course, everything on <a href="http://www.strobist.blogspot.com/">Strobist.com</a>, plus reading the EXIF data/stobist info from examples posted to the strobist flickr group.</p>

<p>Again, I'm grateful. The responses to my previous posts have yield helpful discussion well-beyond the question asked. They're good to read. So thanks.</p>

<p>And again, best for a terrific holiday- Enjoy your time with family and friends-</p>

<p>Shooting "on the fly" such as candid street journalistic type shots, (AUTO) anything will never produce consistent results. Reason? ETTL/iTTL or whatever anyone desires to call it is based of the subject you are metering. Coming into play is metering mode, matrix, center weight, Tv/Av. Far too many variables to expect consistent results.</p>

<p>When I shoot street shots, I always require a test shot or two in order to get the look I want.<br>

I shoot 100% full manual, camera AND flash. The limitation to this is that I must compose from approx the same distance every time, which is ok since the days shooting is based on a style I want that day.</p>

<p>That being said, the auto modes do work and work well in "other" situations as long as certain variables do not deviate too much.</p>

<p>I shoot Nikon, so I can't comment with any expertise how their flashes evaluate and communicate with the camera.</p>

<p>A feature I find invaluable is Nikon's FV lock (Flash Value) Lock. It essentially locks the flashes output regardless of recomposing or changing light conditions.</p>

<p>"I get terrific, but sometimes unexpected, results using FEC"<br>

What type of unexpected results are you getting ?</p>

Thanks, Kevin. Yeah, I should have been clearer. I always shoot in manual, typically spot meter, and shoot a few test

shots of the scene before approaching a subject. I set my exposure based on those tests.

 

 

Your approach--fixing the distance--is a good one. But it's limiting, like you say. Wondering if there's a more

plastic approach.

 

 

Thanks again-

 

PS: your pics that pop up on the page are terrific.

@Harry (hi):

 

2 shots, same location/orientation. 3pm winter day light. Very pretty.

 

 

Shot 1: 1/60, f/8, iso 200, fec -1, subject maybe 4" from flash. Lovely.

 

 

Shot 2: 1/15, f/16, iso 200, fec -1, subject maybe 4" from flash. (I wanted to blur, a bit, the pedestrians in the bg,

while the flash freezes the subject) subject is completely bleached out.

<p>"Shot 2: 1/15, f/16, iso 200, fec -1, subject maybe 4" from flash. (I wanted to blur, a bit, the pedestrians in the bg, while the flash freezes the subject) subject is completely bleached out."<br>

First of all I would not be using the Spot Meter function for flash since most flash average out the scene before firing . Second if you wanted to blur the background a little bit you would open up the aperture not close it down. You would use f5.6, or f4, or f2.8 instead of f16 which actually increases the Depth of Field. Third if you were in any of the Automatic Modes "P", AV, TV then your results might vary. Not sure about the Metz flash, but some flash have a Range Coupler which displays the Maximum flash-to-subject distance for your chosen shutter speed, aperture and ISO. Once you get the maximum distance you place your subject about 1/3 away from that distance to avoid drop-off(black background). Some flash tend to put out more light when using the smaller apertures to compensate so it could be that your subject was too close to the flash in the second example. </p>

 

Hi Harry. Yeah, I should be clearer:

 

In reverseish order:

 

1) I shoot in manual.

 

 

2) blur=motion; not blur=bokeh. The blur effect is one of people moving while the subject is frozen by the flash.

 

 

3) Will try evaluative metering again, but have had sad results with it vis. ambler light.

 

Your rule/suggestion on flash-subject-distance sounds real solid. I'll give it a shot. Thanks so much.

<p>If you are the sort that likes to learn from books, and dont mind learning from a Nikonian, you might profit from picking up a copy of <em><strong>'Hot Shoe Diaries' </strong></em>- one man's attempt to explain a lot of his own personal techniques using etxernal hot shoe flashes in a wide variety of situations. Of course, after reading his specific technique, to understand his concept and approach to the shot, you would have to translate that concept to your own equipment. I've skimmed this book and its very practical looking, and written in 'street language' voice, so not boring at all.</p>

<blockquote>

<p>2 shots, same location/orientation. 3pm winter day light. Very pretty.</p>

</blockquote>

<p>Can you post these?</p>

Thanks Alan, it's a terrific book. Ditto Joe McNally's vids on YouTube. But the technique I'm after is somewhat specific

to the challenge of a single off camera flash, it's output controlled by a specific camera feature. (Canon or Nikon; each

has a similar feature, so the vendor ain't the issue.) That said, McNally's discussion in the book is a terrific jump start.

Thanks again. Best wishes for the holidays.

Hi Jeff. When I'm back at my desk and off my magnificent iPad, I'll post. I can never get the email-posting

thing to work on photo.net.

<p>As Kevin explains, you can't rely on ETTL for consistency. I use ETTL for shooting weddings but in order to do so without the luxury of setting up, I get very good at predicting how the flash is going to 'react' to subject conditions. So in your example for Harry, depending upon how the pedestrian changes the scene, I'd have to FEC-adjust again. I have the dial on my 580EX set to direct adjust, so I can just reach up and adjust FEC. However, I've never had a problem adjusting FEC on the camera by feel either (between frames). It is still pretty fast.</p>

<p>Do some searches on ETTL. I can tell you that it over reacts to white and light colors (underexposure) and I prefer to use averaging flash metering indoors. Outside, I prefer evaluative because this will mostly further cut the flash level automatically, above a certain EV, allowing you to use very small amounts of flash.</p>

<p>As for your situation, if your subject distances stay pretty much the same (or you can force them to be pretty much the same), I'd use the flash in manual mode. Since you don't have partial power control, I'd test the flash (full power) with the Lumiquest softbox on, at the subject distances you use, for the f stops you like, and arrive at a workable ISO. Then stick to it. You can transpose in your head when needed, or make yourself a cheat sheet.</p>

<p>For instance, since guide numbers change with zoom angle, I'd start by manually zooming the flash head to 28mm (the widest). Zooming wide means the guide number (I think in feet) is approximately 50 (from 98 at the 50mm zoom angle), at ISO 100 (you should check your manual). So, using the guide number formula, you now have ISO 100, f8, and a subject distance of 6.25 feet. Putting the Lumiquest Softbox on takes away a stop and 1/4. So now, keeping ISO 100, and f8, you have a subject distance of 4.25 feet (everything is approximate).</p>

<p>Three things. 1) Zooming the flash head wide inside the Softbox actually helps spread the light around, and brings the flash power down (since you want to use fairly close subject distances). 2) The equivalent in stops, to affect subject distance is a factor of 1.4x. 3) It is best to arrive at your own guide number for the combo, since manufacturer's guide numbers are optimistic. Outside, you don't have any peripheral reflectivity to help you, so guide numbers need to often be altered by a stop, toward the down side.</p>

<p>Your cheat sheet should start to look like the following: f11--3 feet, f8--4 feet, f5.6--5.5 feet, f4--8 feet. This is all for ISO 100. You'd size up your situation, place the flash combo at the subject distance you need to for the f stop you want, and test. Unfortunately, for your blurred pedestrian shot, you'd have to move the flash for the 'new' aperture, given you slow the shutter and keep the same EV.</p>

<p>@Nadine- your response is gold. Incredibly helpful and I'm grateful. I'll noodle with it and get it into practice. Thanks, and best for the holiday and new year-</p>

<p>You can also decide to get better at predicting ETTL. Try averaging flash metering, even outside, to see if you like it better. The advantage of ETTL is that you will probably (not necessarily always) have faster recycling, and you won't have to fiddle with physically moving the flash for every f stop change.</p>

I'm not sure if this is flash for main light or fill. But since you've calibrated your flash, and have a Guide Number, for "flash for main light", have you considered shooting at fixed flash-to-subject distances?

 

 

Years ago I had a flash I rated at GN 80 with ISO 100. I limited my shots to 3.5, 5 and 7 feet, and f/8. These distances were close to 1 f-stop differences. So I prefocused by the lens barrel (all three distances are marked on my 35mm and 85mm), set the power ratio, and walked into each shot. Eg. ISO 100 at 5 feet and f/8, with power ratio at 1/4. I was using an L-type flash bracket.

 

 

 

 

It solved dim light focusing problems for me. DoF at f/8 is pretty good, and 1/4 power is short duration. I believe this is an old time photojournalist strategy. Don't worry about the framing. Get the shot in focus and well-exposed, then crop as necessary.

 

 

Good luck.