Question regarding on-camera flash

[Digital]

I went over the instruction book for my flash in using manual as opposed to iTTL. Pretty straight forward until I came to the part regarding how to determine aperture or shooting distance. Wish I had a calculator with me. If I remember correctly, in the film days, and using a prime lens it was: GN/distance = aperture.
Does anyone use the method of trail, and error in selecting the aperture, ISO, flash output, and flash to subject distance. I guess this method may come with experience and/or a good flash meter (which I can not afford).
BTW: Manfred, I have been employing bounce flash for several weeks now.

Bruce

[Manfred M]

I went over the instruction book for my flash in using manual as opposed to iTTL. Pretty straight forward until I came to the part regarding how to determine aperture or shooting distance. Wish I had a calculator with me. If I remember correctly, in the film days, and using a prime lens it was: GN/distance = aperture.
Does anyone use the method of trail, and error in selecting the aperture, ISO, flash output, and flash to subject distance. I guess this method may come with experience and/or a good flash meter (which I can not afford).
BTW: Manfred, I have been employing bounce flash for several weeks now.

Bruce

Without a flash meter, it's called taking a test shot and looking at the histogram. It might take you a few shots to get there, but is far faster and more useful than trying to caluculate the exposure based on the GN.

[Digital]

Without a flash meter, it's called taking a test shot and looking at the histogram. It might take you a few shots to get there, but is far faster and more useful than trying to caluculate the exposure based on the GN.

Manfred, I am very glad to do as you suggested since the method you are referring to seems easier than running around with a calculator. Also, I learn better by the trail, and error method.

Bruce

[Digital]

I was experimenting the other day with on-camera flash. In this photo, I bounced the flash off of the ceiling. I used an index card to bounce some light into the face. The pics were all underexposed; I had to shoot them quickly due to a time factor.
They were underexposed about a stop. On close up there is some noise. Need to figure out what caused underexposure.
Used Auto for WB. Flash was in iTTL mode.
I have a particular question: does this subject's face appear to red? If so, is this a WB problem?
Any other assistance will be greatly appreciated.

Bruce

[Manfred M]

I was experimenting the other day with on-camera flash. In this photo, I bounced the flash off of the ceiling. I used an index card to bounce some light into the face. The pics were all underexposed; I had to shoot them quickly due to a time factor.
They were underexposed about a stop. On close up there is some noise. Need to figure out what caused underexposure.
Used Auto for WB. Flash was in iTTL mode.
I have a particular question: does this subject's face appear to red? If so, is this a WB problem?
Any other assistance will be greatly appreciated.

Bruce

1. The face has a primary red cast and a small secondary yellow cast.

2. When bouncing, I tend to aim the flash head behind or beside me, rarely in front of me. Having the light come down from a position between me and the subject will tend to cause the eye sockets to add a bit of shadow to the eyes. I see that and I don't see the white card doing much for you in this shot.

3. When shooting bounce in this type of situation, I do not use the iTTL mode (I don't trust it). If you use it, use your histogram and use the FEC (flash exposure compensation) as well as the EC (exposure compensation) to get the right balance of light.

[Digital]

Manfred, thank you so much for commenting. Was the reddish cast, and the small secondary yellow cast caused by an improper WB setting?
Your statements in point #2 are really appreciated. In this particular shoot, I did not think to bounce the light from the side or behind me. I need to experiment more.
As far as point #3 , I really want to shoot in manual mode eventually. I believe I will understand flash dynamics better. At home a few days ago, I did experiment with the flash in manual. Will keep experimenting.
Final point, I believe the underexposure was caused by not having enough flash power in relation to the flash to subject distance. Would very much like your opinion.

Bruce

[Manfred M]

Manfred, thank you so much for commenting. Was the reddish cast, and the small secondary yellow cast caused by an improper WB setting?

What WB setting are you using? If you are shooting AWB, then the answer is likely yes. Raw data is easy to correct, but if you want a good SOOC view, I find AWB does not give you repeatable results. If the camera has a flash or daylight setting, try those instead.

Your statements in point #2 are really appreciated. In this particular shoot, I did not think to bounce the light from the side or behind me. I need to experiment more.

Exactly.

As far as point #3 , I really want to shoot in manual mode eventually. I believe I will understand flash dynamics better. At home a few days ago, I did experiment with the flash in manual. Will keep experimenting.

Honestly, you will understand them better shooting on manual. The problem I have with a lot of the automation modes with the cameras is I don't quite know what is happening under the hood. The only ones I tend to use are aperture priority and shutter priority.

Final point, I believe the underexposure was caused by not having enough flash power in relation to the flash to subject distance. Would very much like your opinion.

My gut reaction would be no, but if you were shooting at a very small aperture and a low ISO setting, yes, you might have topped out on the flash. The same thing can happen if the flash has not charged up completely between flashes, so diagnosing what is going on without more information on the room. the camera and flash settings, it's just guess work.

[Digital]

Manfred, thanks for your quick response. I need further experimentation to assure consistent results in my photography using flash.
You have been a real good mentor to me.

Bruce

[inkista]

Just to add to the white balance knowledge, the light from your flash tends to be one color while the light from ambient can be another. Mixed light white balancing can therefore be a bear.

If your ambient light is warm, but your flash tends to be cool, then adjusting for the ambient can make the flash illumination bluer; while adjusting for the flash can make the ambient oranger. So part of the question here, too, is what was the ambient light? And how did you balance flash against the ambient?

If the mix gets really obnoxious, you can consider "gelling the flash" to match the ambient. This means putting a piece of colored plastic over the head of the flash to get it to emit a color closer to that of the ambient, so white balance adjustments in post will affect both equally.

You can also go the opposite direction to make color effects.

In terms of the "bounce card" and aiming behind you, here's an image I took with bounce flash when I was starting out and wanted to play food photographer:



I was using a Canon XT with (of all things) an adapted Leica Summicron-R 35mm f/2 lens on it. f/2, iso 800, 1/200s. Pretty close to ambient settings. My key (main) light was actually the light coming from the window. I was bouncing an on-camera 580EX as fill (@1/8 power). I bounced the light behind my right shoulder (i.e., to get the light to come from the opposite direction of the window light), and I flagged off the front of the flash with a sheet of black craft foam (aka the Black Foamie Thing), so there was no direct light coming from the flash head to hit the lunchbox--all of the light was from the ceiling/bounce surface. That's why the light is all so soft and basically looks like, well, "natural" light.

In your image, the direct light from the bounce card/head of the flash is what's causing that white highlight on the nose, as well as the sharp shadow on the wall right behind your subject. Bouncing behind your right or left shoulder, slightly above head height, at a 45º angle to your subject would probably have given something more like studio light. It's like bank shots in pool/snooker: angle of incidence = angle of reflectance. Or, as Neil van Niekerk has said, aim for the spot where you'd put a softbox if you were studio lighting.

The other reason the shadow behind your subject is so sharp is that he's really close to the wall. Pulling him farther away from the wall would soften that shadow. And as less of the light from the flash would hit the wall, you'd then have the ability to get more separation between subject and background--more of a 3D feel as it were.

This is an off-camera flash example of a similar situation (me at Comic-Con in the front hall, shooting Karen Berger and Mike Carlin):



They're about 7 or 8' from the wall, and I'm using a YN-560 in an 8" softbox, held up in my left hand, and angled from arms' length. I'm using my 5DMkII and 24-105L @f/4. iso 400, f/6.3. 1/160s because the Rf-603 radio triggers I was using to fire the flash add a propagation delay, and a 5DMkII only syncs up to 1/200s (bigger full frame sensors take longer for that gap to sweep across the sensor). I'm probably about 3-5" away from the two of them, which is why there's any softness at all. 8", while a lot bigger than a speedlight head, is still peanuts in modifier size for making soft light.

Note how the distance between the wall behind them has helped me out here. The shadows on the wall are softer, and there's a "spotlight" look to them, because I was able to balance the flash/ambient more towards the flash--the white wall's far enough away that that ol' inverse-square light drop-off makes it darker (less lit by flash). And this helps me de-emphasize that the hallway is essentially people-lined , and to throw more focus on my subjects.

This is, again, why shooting in M on the camera is great for shooting flash--you can deliberately underexpose the ambient with precise control. Exposure compensation in one of the auto modes lets you do this, too, but M is more direct, since you know exactly whether it's iso, aperture, or shutter speed you're manipulating.

[Digital]

Kathy, thank you for commenting. This pic was shot @ f/6.3, SS-1/250, and an ISO - 400. I shot 5 pics all total. I started out at f/8; however I kept stepping up because the photos were underexposed. Due to time constraints, I did not have more time to experiment. Looking back on it now the underexposure could have been caused by a number of factors: aperture setting and/or ISO setting. . At first I wondered whether the flash to subject distance had something to do with it; however (given the reflection on the nose) I think I maybe wrong on that theory. If time was not a factor, I would have preferred to experiment in manual mode on the flash. As I stated to Manfred, I believe this is the best way to learn about flash photography. To your point about shooting in manual mode on the camera, I have been doing this already.
As far as WB goes I never gave it a thought about WB from the flash, and WB from the ambient light. (Incidentally, that is why I shot at a SS of 1/250. I was trying to decrease the effect of the ambient light). I am shooting in RAW so changing the WB in post does not appear to be a problem. Geling the flash is not a bad idea either.
As far as bouncing the flash behind me (right or left shoulder) , your comment confused me. Are you still talking about most of the light from the flash bouncing off the ceiling, and/or a wall. This of course is dependent on the height of the ceiling. If you are talking about primarily a wall, the distance from flash to wall may be a factor, especially in the room I was shooting in. The ceiling height is not a problem. Also, in my mind, shooting BEHIND your shoulder at a 45 degree angle does not seem to equate angle of incidence = angle of reflectance relative to your subject. I need clarification on this point, if you don't mind.
Kathy, any other assistance you can give me will be greatly appreciated. Thanks again.


Bruce







One thing I have learned from all this is to experiment when time allows.
Kathy, thanks again for your assistance, and other pointers you can give me will be greatly appreciated

[Manfred M]

I started out at f/8; however I kept stepping up because the photos were underexposed.

If you are shooting iTTL and stop up, the camera / flash will respond by reducing the light output of the flash, so in effect nothing will change, from an exposure standpoint.. If you had been shooting on manual, the result would have been what you were looking for. This is why I suggested shooting manual, as you know what you are controlling. If you want to change the amount of light hitting your subject using iTTL, you need to change the exposure your camera is looking for by changing the EC and / or FEC , which I suggested in posting #45.

The way to check if any there is any significant impact from the ambient light, use the same ISO, shutter speed and aperture settings and shoot without flash. Whatever you see is the ambient light impact. My guess is that you would have had little to none, give the data you shared with us..

Gelling flash is only necessary if there is a significant ambient light impact. My SB-900 came with gels for both tungsten and fluorescent light and for my large studio flash I have a whole set of CTO (Colour Temperature Orange) that I will use when I shoot under conditions where tungsten light does contribute to the scene. I also have CTB (Colour Temperature Blue) gels, so I could gel the tungsten light source instead of the gelling the flash.

When you bounce light off a ceiling or wall, your light source is centred where the "hot spot" from your flash hits, so this is effectively where your light source is coming from, just as if you had a soft box at that location.

[inkista]

... As far as bouncing the flash behind me (right or left shoulder) , your comment confused me. Are you still talking about most of the light from the flash bouncing off the ceiling, and/or a wall. This of course is dependent on the height of the ceiling.

Yes. You lose light to bouncing. The light has farther to travel when you're bouncing (to the surface and then from the surface to your subject), and there's that inverse-square fall off issue. This is why when bouncing your flash, you might still be using higher ISO, going up into 1600 and higher settings. Larger venues tend to make bounce less viable as a technique.

This is also one of the reasons we really really like doing off-camera lighting with larger light modifiers to soften the light instead--you have more light to work with, and more freedom on where you can place the light. Bouncing restricts you to available bounce surfaces. A light on a stand can go just about anywhere.

... If you are talking about primarily a wall, the distance from flash to wall may be a factor, especially in the room I was shooting in. The ceiling height is not a problem.

You can also use the ceiling behind you.

.. Also, in my mind, shooting BEHIND your shoulder at a 45 degree angle does not seem to equate angle of incidence = angle of reflectance relative to your subject.

Right. I didn't mean 45º behind my shoulder. I meant at an angle behind my shoulder so that the light source would be 45º from the subject. You have to eyeball and judge what angles you're using so the light actually reflects to where you want it on the subject (hence the angle of incidence/reflectance thing) It doesn't HAVE to be 45º, just that that's a common choice for portrait photography. You can also just think of it as "where's the spot I want the light to come from?", and aim the flash head there, if all the angular stuff is confusing you.

[Cantab]

Bruce, do you have a white balance card that you can take a test shot of at the start of the shoot? That would presumably make adjusting the white balance in Lightroom or whatever you use much easier -- unless Kathy or Manfred have contrary thoughts.

[Digital]

Manfred, I feel like a complete idiot. Of course, if you change your aperture in iTTL, in my example, then the flash will compensate for the wider aperture by reducing the output of the flash.
In regards to Kathy's statement about bouncing the light from the flash behind your shoulder, could you clarify that for me. E.G. If your flash is aimed at a 45 degree angle at the ceiling behind your shoulder then it would seem to me that most of the light would fall behind you, and less towards your subject. Angle of incidence = angle of reflection. Something tells me I am missing an important point regarding this issue. Given your statement about a "hot spot" and the light centered at that spot, which in turn this light source acts as soft box.

Bruce

[inkista]

As light travels, it spreads out like a cone as it goes. It isn't like a laser beam that all travels in a straight line. The bounce surface you hit with the flash will radiate the light outwards and effectively become your light source.



We say behind the shoulder, because that generally gives a better angle at typical subject distance. You point it forward, and the angle may be sharp enough that you're lighting from the top (eye racoon shadows), rather than from the side. But of course, this depends on subject distance, and bounce surface distance.

[Digital]

Kathy, thanks for the diagram. This diagram assisted me in making more sense of it all.
Thanks again for your instruction, and patience with me.


Bruce

[Loose Canon]

Hi Bruce!

Something I did a pretty good while back.

Might give you some ideas...

...or not!

[Digital]

Hi Bruce!

Something I did a pretty good while back.

Might give you some ideas...

...or not!

Terry, thanks for the link. Your thread was very informative. All these shots were made in TTL?

Bruce

[Loose Canon]

Yes but with a FEC of +1-2/3.

I was looking for a run-and-gun solution.

[Manfred M]

Thanks for the link Terry. I remember it now.

Your flag on the Speedlight is essentially the BFT (Black Foamy Thing) Neil van Niekerk writes about.

I've got to try that one of these days. Where did you source the black foam?


Bruce - Terry shoots a Canon and if I remember you shoot Nikon. I seem to remember reading that the FEC implementation is quite different in these cameras. I seem to remember that Canon has integrated the FEC / EC whereas with Nikon they are completely separate controls.