Strobes and photograhing children....

[johitchcock]

Hi everyone

I've encountered a bit of an issue which I am hoping you can shed some light on and help with for me....

I have some (admittedly pretty cheap) strobes set up in a home studio and I have been photograhing a lot of children. Now usually I set my camera settings to 1/125s at f11 for studio work, but I understand that for photographing children it is better to try to stick to a shutter speed of 1/200 or faster (feel free to correct me if you think any of these settings are wrong to begin with!).

The problem is that if I use a shutter speed any faster than 1/160 then I start to get a portion of the image coming out black (like a black stripe going vertically from the edge of the frame into the image - how wide this is depends on how much faster than 1/160 I go) - which I understand to be due to the fact that the shutter speed is too fast for the flash synchronisation.

Now this leaves me with a dilemma, as I am finding (especially when shooting toddlers) that quite a few of my images are not completely sharp. Since they tend to be the shots where the kids are moving around I have decided that this must be due to a too-slow shutter speed (although if anyone can also suggest what focus modes to use for kids I'd appreciate it!). Also i have some shots where the kid is in sharp focus but their hands are blurry because they were flapping them around, which in this case i know is definitely due to the shutter speed.

So I guess my question is: is the max synchronisation speed of most studio lights this slow, or do most strobes have a faster max synchronisation speed?

I'm just wondering whether I basically need to go out and invest in some better lights that allow me to use a faster shutter speed, or if in fact I'm doing something wrong and I should be able to make it work with my current kit???

Thanks so much

Jo

[I @ M]

Jo, the black strip you are seeing is either the front or rear curtain of the shutter travelling across the sensor and yes it is due to the fact that your camera is built to have a 1/### as a maximum synch speed.

New strobes will not cure it.

A set of dedicated triggers that will allow the strobes to fire at higher shutter speeds can be obtained easily --- at a price.
The triggers work by "fooling" the camera and introducing a delay / advance to when the trigger tells the flash to fire in relation to the shutter actuation.
They work best (apparently) with strobes that have a long flash duration.

Check out the pocket wizard flex and mini tt triggers. They are pricey but work very well. I can reliably trigger studio strobes at 1/8000 with them (http://www.ausphotography.net.au/forum/showthread.php?101044-Frozen-motion-in-the-studio).
It is a bit of trial and error with them but once you learn how to program them to suit your camera / strobes they are foolproof.

[mikec]

Correct me if I am wrong..... but another solution would be to drop your f/stop to say f/8 (you won't miss the extra DOF I'd imagine) which will then allow you to decrease the power of the flash and thus shorten the flash duration. You could alternatively increase your ISO to achieve the same effect, you might even try both f/stop and ISO.

By decreasing the flash duration you get a shorter pop which will mean you've effectively decreased your exposure time and you should remove some of the motion blur from the moving kids. Because remember in flash photography the flash creates the exposure and the camera settings only control ambient light levels.

This is a good article (http://www.cameratechnica.com/2012/01/18/high-speed-photography-with-your-flash/) that explains it well.

[I @ M]

Mike, unless I am mistaken Jo is talking mostly about studio strobes or monoblocs and the vary greatly from speedlights in that most of the cheaper units have a fairly long flash duration. Somewhere between 1/750 and 1/1500 is fairly common. With those units the actual flash duration doesn't alter much between full power and minimum power and in fact can often be shorter at full power.
There are some units with an extremely short flash duration and most of those run into the thousands of dollars per head. :(
The article that you linked appears to deal only with speedlights and they are ideal for doing the job but in a studio situation where bright sparkling images of kids are wanted they are found wanting because of their much lower power output. Of course, one can use multiple speedlights placed strategically to provide high levels of light in the scene but once again, the dollars needed to buy 4 or more enter into it. :(
With studio strobes you face the choices of paying big bucks for super expensive heads or to buy triggers such as the pocket wizards to allow above normal flash synch speeds.
Unfortunately I don't subscribe to your theory of simply opening the aperture and hoping for a shorter flash duration to do the job.

If you want brightly lit studio shots you must have lots of light ( or big reflectors ) and the way to expose for that is by the aperture. Add more light to cover a larger area means that you stop down in aperture as that is the only way to manage the exposure until you get into very high shutter speeds which do have an effect on incident lighting.
Generally studio situations don't have a huge amount of ambient light coming into play and in many cases may be dark except for the light from modelling lamps. Even with moderate levels of ambient light ( not direct glaring sun ) entering the room at base iso levels and moderate aperture and power settings the flashes will overpower it.

As an example, the image below is shot at 200 iso 1/160 F/6.3. There was plenty of indirect ambient light entering the room but it does not feature in the exposure. Movement is far from being frozen and from past experience to stop that blur happening in a studio you must go over the max synch speed of the camera which in our case is ( supposed to be ) 1/250.
The motion blur in that image is there on purpose, I feel that some movement adds to shots like these. If I had wanted to freeze all action I could have easily done it by going as high as 1/8000 shutter speed.

http://dl.dropbox.com/u/9582534/IAM_9393.JPG

[mikec]

Andrew you are right about studio stobes / monoblocks vs. speedlights with regards to flash duration. I must of glanced over when she said strobe I'm doing a lot of work with speed lights so the lighting part of my brain is in that world at the moment.

Hopfully Jo can confirm if she is using studio strobes since it would solve our discussion. If she is, you are indeed right and she will either need to invest in a PW system or better lights.


Unfortunately I don't subscribe to your theory of simply opening the aperture and hoping for a shorter flash duration to do the job.

It could but it depends on the desired outcome, but my whole reply is a bit of a moot point since we are mostly talking studio lights here and my reply was addressing speed lights.

I'll admit all my studio work has been done in a uni studio with decent lights and light meters (we shot on film, so no chimping) so I've never had a huge issue with getting desired outcomes using diffused and reflective light readings with a meter.

[johitchcock]

Hi guys thanks for your replies. I'm out ATM so will go into more detail later but I am talking about studio strobes and not speedlights. I'll try to dig out the tech specs for the lights later :-)

[Tommo1965]

my D300s has a 1/250 sync speed, but I could never shoot at that speed without seeing the second curtain..so I shoot at 1/200... admittedly this was using really crappy radio triggers.. I've since bought some Cactus V5 triggers..Im not sure they will work any better in this regard..but im hopeful

in my home situation ambient light doesn't affect exposure at 1/200...but as Andrew said it wont freeze action either ...and I doubt 1/250 will

[Tommo224]

Those MiniTT1 that were mentioned, will they work on cheaper brand Strobes? Ie: Yongnuo.

So a faster flash can be used? That's how it works yeah? I can shoot faster with flash as at the moment minimum I think is 1/250. Anything faster than that gives me the black line :(

[I @ M]

Those MiniTT1 that were mentioned, will they work on cheaper brand Strobes? Ie: Yongnuo.



The short answer is I don't know. :confused013

The long answer is that pocket wizard make the units as Canon or Nikon specific so that they allow ttl metering with those brand speedlights by radio signal instead of optically as in the Nikon commander mode.
Therefore I guess that the yongnuo won't have the necessary capabilities built in just as they probably don't when you try to run them on the cls system.
Seeing as only the centre pin on the contacts is used to actually trigger the flash from memory they might work as a dumb radio trigger but to buy them would result in paying a helluva lot more to do what the yongnuo triggers do.

[mikec]

Look at the pocket wizard website, they have good documentation with what flashes work with their triggers.

With that in mind I believe they will function as a basic trigger but not allow any TTL functionality. Not sure if they will allow the hyper sync function to work though.

[Tommo224]

The short answer is I don't know. :confused013

The long answer is that pocket wizard make the units as Canon or Nikon specific so that they allow ttl metering with those brand speedlights by radio signal instead of optically as in the Nikon commander mode.
Therefore I guess that the yongnuo won't have the necessary capabilities built in just as they probably don't when you try to run them on the cls system.
Seeing as only the centre pin on the contacts is used to actually trigger the flash from memory they might work as a dumb radio trigger but to buy them would result in paying a helluva lot more to do what the yongnuo triggers do.

Oh I see! Thank you for that :)