SB-600 flash reach

[tom beard]

I've researched the forum threads and learned that there are so many variables it's almost impossible to determine how far away from the camera/flash an object in focus can be lit. It is obvious that the light intensity will fall off a certain percentage for each foot of distance it travels to reflect off an object so that the image can be recorded by the sensor, etc, etc. That's way to technical for me. Could any one who uses a Nikon SB-600 tell me your practical experiences with 'reach' under different circumstances?

Thanks as always, Tom Beard

 

[chip]

the reach depends on the ISO speed setting and lens used. I have a SB800 and it has a motorized zoom head that goes from 28 to 100mm? A zoom head extends the reach. In general when shooting with a telephoto lens you will have farther reach than when using a wide angle lens, provided your flash has a zoom head. Kirk Photo also sells a flash extender for telephoto lens.

 

[Derrel]

http://www.nikonusa.com/pdf/manuals/Speedlights/SB-600.pdf

From page 76 of the manual:
With the SB 600 flash zoomed to its maximum 85mm position,at ISO 800 the Guide Number in Feet is 147; at ISO 400 the GN is 105; at ISO 200 the GN will be only 73

So, let's say we need a long reach shot of a speaker at a podium, indoors, or a high school basketball player shooting a layup from the stands. We'll need an 85mm lens for the shot, to get tight enough framing from a long distance.

Let's say we are at 30 feet, with an 85mm lens and a 1.5x Nikon body; that will give a field of view measuring 8.47 feet tall on a D90 or D300. The 147 GN is divided by the flash-to-subject distance of 30 feet, yielding an exposure of f/4.9, close enough to call f/5.

If you need a longer reach, you could bump the ISO up to 1,000 or 1,250. Another option is to get the flash unit closer to the subject than the camera is to the subject--especially like if you want to capture a shot of deer raiding your garden or something like that, while shooting from the house say 150 feet away--with a remote triggering the flash, the flash-to-subject distance would be much closer to the subjects than the camera happens to be.

Nikon has a formula on Page 76 of the free .PDF manual on-line, allowing you to calculate the maximum shooting distance, based on the varying Guide Numbers that the SB 600 flash has at different beam spreads AND taking into account your lens's maximum f/stop.

The formula is simple: Take the flash Guide Number in Feet and divide that BY the f/stop you wish to use, and that will give you the maximum shooting distance (at a given ISO).

So 147 divided by 5.6 is 26.25 feet,so with a lens that tops out at f/5.6, using ISO 800 setting, the maximum range is 26 and a quarter feet.
And 147 divided by 4 for f/4 is 36.75 feet. 147 divided by 2.8 is a maximum of 52.5 feet, while 147 divided by 2 for f/2.0 is is 73.5 feet. So, if you need to shoot flash at the absolute maximum distance with an SB 600, you need to use an ISO setting of 800 or higher.

The higher-powered flash guns are really worth their price if you need to do long-throw flash. HOWEVER, with the new camera being capable of ISO 3,200 and ISO 6,400 with good quality, flash ranges have been extended dramatically. Using the ISO 800 distances I computed for you, translate of "shift" the above information two full f/stops for 3,200 or three full f/stops for 6,400 iso. For example f/5.6 at 800 iso *is* 800 ISO, and 1600 makes f/5.6 become effectively like f/4, and 3,200 makes f/5.6 become effectively like f/2.8, and 6400 makes f/5.6 effectively f/2.

 

[tom beard]

Darrel, Thanks very much. You are a master technician, but it's late and it may as well be in Chinese. Tomorrow, I will go through your post line by line and read the pdf on the SB-600. I may not get it all, but I'll know a hell of a lot more than I did before writted this post. Many thanks, Tom B

 

[KmH]

Tom, the light falls off as a square function. It's known as the 'Inverse Square Law."

If you double the distance only 1/4 as much light reaches your subject.

If you double the distance again, or now 4 times the original distance, only 1/16 as much light reaches your subject.

The SB-600 can only zoom to 85 mm. The SB-800 zooms to 105 mm and the SB-900 zooms to 200 mm. The SB-400 doesn't zoom.

 

[IgsEMT]

Derrel, love your math!!!
Thanks.

 

[Kegger]

I don't do math.

But I know from experience that I can light a subject at about 80 feet with my SB-600, and make a clean exposure.

 

[KmH]

I don't do math......

To bad. You wouldn't waste as much time by having to do things by trial-and-error.

 

[Gaerek]

You can probably find a flash exposure calculator online somewhere that will help you. I have an app for my iPhone called PhotoCalc that has a few different useful functions, and one is a flash exposure calculator. I've used it with great success in the past.