Question about aperture vs sync speed vs shutter speed

[dearis]

Hi there,

I was wondering if my camera is set to F/4, sync speed at 1/200sec will the background blur in the shot?

Regards Darren

[scottbergerphoto]

I assume your background is stationary. That means that the shutter speed is really irrelevant. Whether it will be out of focus depends on the depth of field of your specific lens set at f/4 and where the subject is placed in relation to the background. There are numerous Depth of Field Caluclators on the web.
http://www.dofmaster.com/dofjs.html
Plug in the information for your lens and you can figure out what f stop to use and how far to place your subject from the background. Remember that DOF is not divided evenly. 1/3 is in front of the subject and 2/3 is behind.

[blundar]

DOF is determined from the following:
1. Distance from subject
2. Lens length (mm)
3. Aperture
4. sensor/film size
5. distance from background

So for example, at 6ft from subject, with a 50mm lens, and f/4 aperture, with a full frame digital camera (Canon 5D or Canon 1ds equivalent to 35mm film), according to the DOF calculator, you end up with 1 ft DOF. So if your background is more than 12 ft away from you then the background will be nicely blurred.

With a x1.6 crop digital camera, you end up with x1.6 more DOF.
Longer lenses shorten your DOF.
The closer you are to the subject the shorter the DOF.

Get familiar with a few lens lengths (28mm, 50mm, 100mm, 200mm), at a few different distances from subject, and f/stops, and you will get a real sense of what you will be getting for results.

[dearis]

Cool thanks, found this as well http://www.photonhead.com/exposure/simcam.php should be helpful.

Regards Darren