Avoiding Ghosting when using Strobes and Ambient Light

<p>I understand that ghosting comes when your ambient light is at about the same level than your flash. So for me to avoid ghosting I have to set my shutter and aperture to meter -2EV. Well, I have been watching videos by Annie Leibovitz and have noticed she is using one single light modifier on location to get pictures like these:</p>

<p><img src="http://getdressed.typepad.com/.a/6a01156f7b45d3970c0120a64932b9970c-800wi" alt="" /><img src="http://sphotos.xx.fbcdn.net/hphotos-snc6/7227_181295832278_42933792278_4166531_3657813_n.jpg" alt="" width="460" height="320" /><br /> So, these images do not look as if the ambient was underexposed, they look balanced. I also know there is a lot of editing on magazine covers so my idea is that she underexposed and fixed in post. But am I right?</p>

<p>Why under expose? The key is to supply more light to keep up with the sun. You need a more powerful flash. There's a reason that you'll see pros on sets like that shooting with a couple thousand watt-seconds of flash power.</p>

<p>I meant underexpose ambient and expose properly with flash.</p>

<p>The ghosting is caused when the shutter is too slow and so the camera records ambient after the flash has gone off when there is something in the shot that is moving. As long as your shutter is fast enough to stop your subject--not an issue with camera on tripod and shooting a still object--you wont have ghosting.</p>

<p>Actually, thinking about it, I have shot where I drug the shutter for sports shots and didn't get ghosting, it really has a lot to do with the setting and the balance of the light--but again, it doesn't happen with items that are frozen by the shutter.</p>

<p>I've done multiple shots at 1/125th and still get ghosting. I'm going to make sure today that I shoot at 1/250th and use flash as fill to see what I get. Thanks John and Matt.</p>

<p>A good test is to see if you're getting motion blur on your (underexposed, for testing purposes) subject when you don't let the flash fire. If you are, and you want ambient light to play a role, you're going to have to go to a higher ISO and/or wider aperture so that you can support a faster shutter speed ... and of course you'll have to go to high speed synch if your camera/flash rig can support that.<br /><br />If you simply can't get the shutter speed higher, you'll have to change your subject's behavior (or your camera movement) so that movement during the exposure isn't an issue.</p>

<p>Are you using a tripod?<br>

I have shot as slow as 30 seconds with flash and as fast as 1/500 on my hassleblads, never ever have I had (ghosting). <br />With ambient light you set the f-stop for the flash and shutter speed according to the ambient light if you want it all balanced. Faster shutter speeds lower the ambient light, slower shutter speeds increase the ambient light in the photo.<br />If you are getting blurred images use a tripod.....its not the light but camera movement.</p>

<p>I have been writing about this issue in the past, here in photonet and other places.<br>

To equilibrate the ambient light do this:</p>

<p>First: shoot in manual, not in automatic (you can shoot in automatic but the method is slightly different).</p>

<p>FIRST: Read the light (no flash) in the background for a exposure time compatible with flash whooting (p.e. 1/60)<br>

SECOND: Read the light in the figures (with NO flash).<br>

THIRD: Adjust in camera the exposure for the background (f ant t).<br>

FOURTH: Change the f number in camera in this way:<br>

If the difference beetween the figure and background is 1 stop, adjust in the camera the same f number you read for the figure.<br>

If the difference beetween the figure and the background is 2 stops, use in the camera a 1+1/2 stops grater than the figure.<br>

If the difference beetween figure and background is 3 or greater stops, adjust in the camera the same f number you read for the background.<br>

FIFTH: Adjust in the flash the power. To do this aim the camera to the figure with flash on. Focus the figure. Now read in the flash display the distance from the flash to where it will give you the f adjusted in camera.<br>

Change the power until you can read in the flash display the distance beetween the flash and the camera. <br>

So you now have the power adjusted exactly to reinforce the light of the background.<br>

SIXTH: now change the f adjusted in camera to the f for the background.</p>

<p>So, you end with the camera adjusted for the background (f and t) and the flash in manual with the correct power to equilibrate the ambient light (I prefer call this "reinforce the light" than "fill the light").</p>

<p>Great how Leibovitz can get natural light to appear to come from a different direction for each model, don't you think? And without the shadow of one model falling on another too. That cover couldn't possibly be composited, could it?</p>

<p>As others have already said, avoiding ghosting is down to the shutter speed relative to any camera/subject movement, and not the degree of exposure. If you leave the camera in Aperture Priority or Program mode for flash, then ghosting and poor exposure is almost guaranteed.</p>

<p>This is a sample of a photoshoot I did last year. I was shooting at 1/250th and still got some ghosting. I was shooting with an Elinchrom Ranger RX Speed with S FreeLite. Maybe I should upgrade to the A heads? Don't know but this is the problem I am getting on some photos.<img src="http://d6d2h4gfvy8t8.cloudfront.net/15774892-lg.jpg" alt="" width="904" height="497" /></p>

<p>Here is another sample. Same shutter speed set at 1/250 but the aperture is now set at f16</p><div></div>

<p>Erick, it is a little strange than a t: 1/250 you get a displaced image ¿Could it be a self-shadow of the hand (the dark tone the figure takes when its surface change its angle to the light beam)? (Yur photo of the girl in black gown.<br>

For the red one, it is a gohst... ¿Are you sure it was at 1/250?</p>

 

<p>The flash is balanced with the ambient light makes a ghost when there is movement by the subject or camera. The flash is going on and off before the shutter is finished closing therefore what available light is around is exposing the subject again thus making a ghost. <br /> The example above is a little different and occurs when there is a bright background like the open sky and therefor the same flash goes on and off before the shutter closes but instead of the ambient light exposing the subject the subject becomes silhouetted on the outer edges of the body by the open sky as the subject moves or the camera. Again here the ambient level of the background open sky is close to balanced with the flash exposure. It does not have to be exactly balanced it can still be a stop under and still have this affect. A tripod will solve these problems as long as the subject is not moving.</p>

<p>Paco, I am sure it was 1/250th, it's embedded in the exif data as well and I double checked before posting.<br>

Michael, I was hoping there was a fix for this... But apparently there is no super solution for a scenario like this. I know by using a tripod can fix that problem, I was shooting with a 200mm handheld and she wasn't moving much so I am sure it was camera shake but in the case of a snowboarder doing a flip... how do you fix that?<br>

Thanks!</p>

<p>I just read a pretty good article by Dan Carr:<br>

"You might have been able to do it if you had an assistant holding the flash head on a boom directly above my head but that is quite a stretch. For shooting fast moving action at slow sync speeds like 1/250 or 1/320 you need to underexpose the ambient light by anywhere between 1 and 3 stops to prevent ghosting. The impression of ghosting will vary greatly depending on the angle at which your subject is moving in relation to your camera sensor. If they are moving towards you, much of the blur will be towards the camera and hence not visible. If your subject is moving across the image very quickly as in the shot on the left, then you will have to underexpose more to prevent that blur"<br>

<a href="http://dancarrphotography.com/blog/2010/09/13/elinchrom-quadra-review-and-comparison-to-ranger-rx/">http://dancarrphotography.com/blog/2010/09/13/elinchrom-quadra-review-and-comparison-to-ranger-rx/</a></p>

 

<p>That article hit it on the nose. Two stops underexpose the background and your good to go. The other thing is make sure your shutter speed is equal to or faster than your focal length. It is always better to use a tripod and use the panning technique for moving subjects. Good question it got me to think about this.</p>

<p>In that sample with the red dress, I am sure the exposure on the sky was minus 3 stops and still got ghosting. So, even at -3 you may get some ghosting in some cases.<br>

If I could now go back to the main question, how did Annie manage to combine flash and ambient so well? </p>

<p>You said you hand held the camera and therefore you got camera shake. Annie number one was not shooting at dusk so there was plenty of ambient light that gave her fast enough shutter speed and second the back ground is land not open sky.</p>

<p>Michael, it wasn't dusk. I overpowered the sun with 1100w of light from the Ranger RX. That shot was at around 3pm.<br>

If you look at the sample from Vogue, it is at around 5 or 6pm in California, that's why you see that sun on the horizon.<br>

And in the video, she isn't using a tripod either, and also not shooting medium format, so her sync speed had to be at 1/200 max on her Canon.</p>

<p>Every senario is different. Annie was not using a 200mm lens. I see raw sunlight hitting the models. I do not see raw sunlight hitting your subject and I see a very cloudy day. The main reason you got ghosting is that you used a 200mm lense hand held and the sky was not under exposed enough. You say it was 3 stops then it should have been 4 or five for the same senario otherwise if you used a tripod you would have been fine.</p>

<p>That sounds right. I'm gonna practice more on those scenarios.</p>

<p>I was under the impression that 'ghosting' is another form of flare. In which case, the shutter speed would not affect it; only light placement and lens hood use. Most of the posted photos show ghosting the way I have heard it used - that is, loss of localized contrast and sharpness due to stray light hitting the front lens element. The effect is similar to diffraction, but can happen at any aperture.</p>

<p>I wasn't there when the shots were taken of course, but most of the images posted look like the problem described is not movement, but either ghosting (the way I understand the term), or the result of a sensor outresolving the lens.</p>

<p>No Zack you got this confused with something else. This is all about flash and ambient light. Nothing to do with stray light hitting the front of the lens. </p>

I did some calculations to see how far the model would move at 1/10 (.3mph) normal walking speed. Using a 200mm lens on a 2.25 square film gives .14 ft or 1.68" of movement. The dark line looks way narrower than this so it probably isn't model movement even though her hand is blurred. Was the strongest flash up and slightly to camera right? If so the dark line could have been caused by the fill being overpowered by the main. I don't have the equipment to test this out so if this is a reasonable idea and you try it (and if it works) please let me know . Rodeo Joe said the magazine cover could have been composited and it sure looks that way because of the different angles and highlights on the faces. If you are using film, you could set up a digital camera to look at the ghosting similar to using polaroids in the old days but you have probably already thought of this. Good luck.

 

Randyc

Forgot shutter speed and the edit time ran out.

 

The flash goes off at least at 1/10,000 of a second so there should be no movement in the main light area. The dark line (if caused by model movement) is what comes out at 1/250 second ambient shutter speed. At .3mph she would move at 0.44ft/sec (5.28 inches/sec) So how far does she move in the shutter time? With the lens magnification and 1/250 factored in the shutter speed is effectively 1/100sec. Lens mag 200mm/80mm = 2.5 shutter speed 1/250x2.5 = 1/100. Movement then equals 1/100x5.28in/sec or 0.0528 inches about 1/16inch if her movement towards the flash. Still looks like flash ratio will help. Sorry about the miscalculation.