Strobe Lighting Strangeness

[jaydebruyne]

First of all,

Please allow me to say a warm hello to the CiC world - Hello

I'm new here and to photography in general so please bare with me whilst I'm learning the basics. I am aiming to do portraiture work initially (actor head shots, weddings etc) before I move on to creating my own shoots where I can let my imagination run wild.

I do pose one question:

I just bought a set of strobe lights with a soft box/umbrella and a trigger. All works fine and I'm happy with it apart from one thing.

Every picture I take with the lighting rigged up has a dark bottom border. As you can see here:

http://www.flickr.com/photos/jaydebruyne/8123028867/



No matter where I take a picture, I get this border at the bottom, but only when I have the lighting rigged up.

I'm using a Canon 600D with a 50mm 1.8 prime lens. ISO: 100 - F/stop: 3.5 - Shutter: 1/250

I've googled and tried the lighting in different positions but nothing has worked. Can anyone shed any light on this for me?

Thanks in advance.

Cheers
Jay

[JPS]

Hi Jay,
not sure about this and I'm sure others may be able to give better advice.
I cannot make out much from your picture but could it be Optical vignetting? As you are using a 50mm / 1.8 prime lens perhaps this is causing the problem. Optical vignetting is caused by light hitting the lens aperture at a strong angle - an internal physical obstruction. This effect is often noticed in images taken with wide angle and wide aperture lenses used with wide open apertures. Even many of the best lenses have optical vignetting. Light hitting the lens directly from the front is allowed to pass through the aperture unobstructed while light hitting the lens from a strong angle is partially blocked by the aperture. A basketball passes through the hoop (aperture) much more easily if it is coming straight down into it (highly arced - or dunked) than if is is coming straight in from the side (at a hard angle - no arc). Stopping down the lens reduces or eliminates optical vignetting.
Moving your lights / softbox to a different position might help.

[William W]

I just bought a set of strobe lights with a soft box/umbrella and a trigger. All works fine and I'm happy with it apart from one thing. Every picture I take with the lighting rigged up has a dark bottom border.
No matter where I take a picture, I get this border at the bottom, but only when I have the lighting rigged up.

I'm using a Canon 600D with a 50mm 1.8 prime lens. ISO: 100 - F/stop: 3.5 - Shutter: 1/250

It is a Vignette Bar Line caused by the shutter being too fast for the Flash.

Maximum Flash Sync Speed for an EOS 600D is 1/200s.
With some Studio Flash Units you might need to use even slower, for example 1/160s or 1/125s


Image © AJ Group P/L Aus., WMW 2009.

You might wish to research:
 “Focal Plane Shutter”
 “Flash Sync with Focal Plane Shutter” and
 “x-Sync”
Also (for Flash Units capable)
 “High Speed Flash Sync”


WW

[jaydebruyne]

Hi,

Both answers make complete sense - Thank you both so much for getting back to me so quickly and not making me feel like a dumb a**!

*clapping hands* I'm so addicted to photography already!

Thanks again to you both. Here's a snap I took of my dog, Ty, with my aperture set to 7.1, 1/125 and ISO at 200.



Cheers
Jay

[JPS]

Hi Jay,
no dumb questions here; that's what we are all here for; to learn.

By the way, Welcome to CiC, it's great to have you with us.

[Manfred M]

I would suggest that Bill is right on with his answer. You are seeing the effects of the first curtain of the shutter not having reached the bottom position.

With a focal plane shutter at any speed up to the synch speed, the first curtain tavels across the entire focal plane before the second one starts to move. This means that the whole sensor is exposed to the image.

Once you get shutter speeds higher than the synch speed, the second curtain starts its travel before the first one has completely cleared the sensor. In other words, you are getting a travelling slit. Your flash has quite a short duration, usually a maximum of somewhere around 1/1000th of a second, so only the fast moving slit between the top and bottom curtain gets a significant amount of light.

With dedicated flash unit, the camera and flash communicate and a number of things can happen. Generally the camera will automatially limit you to the maximum synch speed. If your camera and flash are designed to handle high speed synch, then your flash fires pulses of light and you can use even the fastest shutter speed your camera can handle.

If you are shooting with either a studio flash or one not designed to interoperate with your camera system, you have to stick with the maximum synch speed of the camera,

[rpcrowe]

I agree with Manfred's remark...
"If you are shooting with either a studio flash or one not designed to interoperate with your camera system, you have to stick with the maximum synch speed of the camera."
However, some studio flash units require that the maximum shutter speed remain quite a bit below the maximum sync speed of your camera. I use some older Paul C. Buff, White Lightning WL-5000 units and the maximum sync speed for these units is 1/60 second. My 7D sync speed without HSS is 1/250 second but I reduce the shutter speed to 1/60 second when shooting with my White Lightning units. The 1/60 second limitation poses no problems since when I shoot with studio strobes, they will be providing all the light for my image and the strobe will stop most motion.
Bill's remark surprised me because I had assumed that the maximum sybc speed of the 60D was 1/250 second as is all the rest of my 1.6x Canon DSLR cameras. I wonder why Canon reduced the sync speed to 1/200. This would place an additional burden when shooting outdoors if you don't have a flash unit capable of high speed sync...

[William W]

Hello Richard,

. . . some studio flash units require that the maximum shutter speed remain quite a bit below the maximum sync speed of your camera.

Yes, thanks.
I was about to re-iterate that point. I made it in my first post and I didn’t want it to be missed.
My Elinchrom Units require about 1/125s.

***

. . . I had assumed that the maximum sybc speed of the 60D was 1/250 second as is all the rest of my 1.6x Canon DSLR cameras. . .

There’s a pattern in regard to the Model TYPE:
The OP has a 600D and the X-sync is 1/200s . . . also the X-Sync is 1/200s on the 500D and the 550D . . . models.

The X-Sync on the 60D is indeed 1/250s: as it is also on the 20D; 30D; 40D and 50D (and 7D)


Regards,
Bill

PS
> Hello Manfred
> Welcome to CiC, Jay
> Nice dog - quite confused by all the carry-on with the new lighting gear, I bet...

[Mark von Kanel]

Hi Jay, if your going to get into lighting pop over to strobist . com a;thought its primarily a small flash site all of the principles are the same for studio stuff read strobist 101 & 102 you will learn heaps!

[rpcrowe]

My error... Somehow, I read the original posting as "60D" instead of "600D"


However, IMO, it is time for Canon to wake up and produce a camera with 1/500 sync speed such as some Nikons have.

I think that the reason Canon keeps the sync speed at 1/200 (Rebels) or 1/250 (other 1.6x DSLR cameras) is because for a long while most third party (Sigma excepted) hotshoe flashes did not have HSS capability. The photographer had a choice of using only 1/200 or 1/250 second sync speed or purchasing a Canon OEM flash.

[Mark von Kanel]

Richard unfortunatley this isnt something that nikon have continued to do. i think the 1d series and the D 70 were the last to have this!!!

[rpcrowe]

Richard unfortunatley this isnt something that nikon have continued to do. i think the 1d series and the D 70 were the last to have this!!!

Maybe they took their lead from Canon. Just goes to show you that change is not always progress!