#1. "RE: sb900 flash overheats" | In response to Reply # 0ScottChapin Charter MemberWed 13-Nov-13 09:38 PM
It is a very common problem. Evidently Nikon got tired of repairing SB800s under warranty. Unfortunately in the day of digital, where we take large numbers of pictures without regard to cost, portable strobes cannot keep up. I know you can push the heck out of an SB800, but evidently you can push it enough to burn one up.
Generally, flash manuals ask to limit the flashes to 15 full power flashes per 10 minutes. In the days of film, nobody would be dissatisfied with this rate of fire. So, if you are shooting 30 full power shots in less than 20 minutes, you are pushing it.
The SB900 has a limit as to how many shots you can take before it shuts down for awhile. As I understand it, the SB910 handles it ala Canon style, in that the cycle times increase and the flash slows down over time.
The problem is that the flash tube, batteries, and circuit board are crammed into a small space and the heat builds up too fast. The reason Quantum Q-Flashes don't have this problem is due to the large open air reflector with the bulb in the open, circuit boards well separated, and battery power a good distance from the head.
The suggested starting point with the SB900 is to use the SD9 external battery pack with LSD NiMH batteries. This helps remove heat build up internally from the batteries. Next is to up the ISO to the extent that you can to reduce the amount of flash power needed. Get as close as reasonable to your subject to reduce the flash power.
I can shoot weddings with an SB900 without problems when shooting closer to 50mm at ISO 400. With my 85mm f/1.4 I have to up the ISO to 800, because I'm getting too far away from the subject.
I use my Quantums when I really cannot take a chance. Of course, when I don't need all of my flash units in simultaneous use, I keep an SB900 in rotation with my 85mm f/1.4.
Powder Springs, GA, USA
Nikonians Team Member
#2. "RE: sb900 flash overheats" | In response to Reply # 0MEMcD Nikonian since 24th Dec 2007Thu 14-Nov-13 03:12 PM
The thermal shutdown feature was added in the SB-900 to prevent the Speedlight from melting when pushed beyond the designed duty cycle. Unfortunately the Nikon Speedlight User Manuals are not very clear on the maximum design "Duty Cycle" for Speedlights. On page F-5 the maximum number of continuous shots is 15 in i-TTL, Non-TTL Auto, and Manual (M1/1, M1/2) then a 10 minute cool down is required to prevent overheating. That works out to one shot every 40 sec. or so. If you are shooting much faster than that, you should consider a Quantum Q flash.
Scott's advise on maximizing your FPM (Frame Per Minute) rate using the SB-900 is spot on.
Using LSD batteries in the SB-900 will also help a little since the low internal resistance reduces the heat generated by the batteries chemical reaction but does not eliminate it.
If you use the diffuser dome, it not only slows the cooling but increases the heat load since the flash will fire using more power and thereby generate even more heat.
#4. "RE: sb900 flash overheats" | In response to Reply # 3PSAGuy Nikonian since 04th Nov 2008Fri 15-Nov-13 06:57 PM
I always carry a spare SB 900 and know the issue but generally plan ways to handle it including Eneloops batteries and an external battery pack.
Not sure how anyone risks shooting a wedding with a single flash. Too many things can happen.
#5. "RE: sb900 flash overheats" | In response to Reply # 0
#6. "RE: sb900 flash overheats" | In response to Reply # 5ctadin Nikonian since 28th Oct 2008Tue 19-Nov-13 12:50 PM | edited Tue 19-Nov-13 12:52 PM by ctadin
Regardless of whether the 900 overheats or not, I always carry an extra flash on my freelance photo shoots.
I had one incident when my 900 overheated. I was photographing a family portrait outdoors, in July, where the temps were in the high 90's. We won't even get into the humidity level.
Because I had a back up flash, I was able to keep on shooting.
I do use Sanyo Eneloops in my flashes.