Guide Number vs Watt Seconds | Ask David Bergman
ฝัง
- เผยแพร่เมื่อ 4 ส.ค. 2024
- Today's question from Eric L. is, “You’ve spent a great deal of time discussing various aspects of flash like high-speed sync, diffusers, and metering. Given all of that, are guide numbers still relevant?”
Go to www.AskDavidBergman.com to submit your own photo question, see David's gear list, and view the episode archive.
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✘ PRODUCTS USED:
Canon Speedlite 600EX II-RT Shoe Mount Flash
www.adorama.com/ca600ex2.html...
Flashpoint XPLOR Power 1200 Pro R2 Flash System (Godox AD1200 Pro)
www.adorama.com/fplfx1200p.ht...
Flashpoint XPLOR 600PRO TTL
www.adorama.com/fplfx600ptb.h...
Profoto B1X 500 AirTTL To-Go Kit
www.adorama.com/pp901028.html...
✘ PRODUCTION EQUIPMENT USED:
Canon EOS R Mirrorless Full Frame Digital Camera Body
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Canon RF 28-70mm f/2 L USM Zoom Lens
www.adorama.com/car28702.html...
Manfrotto MT055XPRO3 Black Aluminum Tripod with MVH502AH Pro Video Head
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CLAR Illumi Max 500 High Power 5600K LED Light
www.adorama.com/clilmax500sl....
Glow EZ Lock Octa Quick XL Softbox With Bowens Mount (48")
www.adorama.com/glsbe
#flashphotography #guidenumber #adorama
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00:00 Intro
01:50 What are watt-seconds for flash photography?
03:22 What does a flash's guide number mean?
05:16 Other factors that affect guide number
07:04 Are guide numbers still relevant?
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Mark Wallace video about watt-seconds:
• Understanding Watt-Sec...
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THANKS SO MUCH FOR WATCHING! - แนวปฏิบัติและการใช้ชีวิต
so thorough and yet so easy to understand! thanks
That coverage of the subject gives a better understanding on setups and how to best judge a new flash unit. Great information to keep in mind when doing studio work to chose the best light to get the best results. Thanks David
Thanks for this, David! I've never had a good understanding of guide numbers on strobes. Now I'll keep that in mind when I am working with a strobe or when I buy my next one.
Thank you David. Great discussion, very helpful.
Thank you, David! I will definitely use this information as I am in the market for a strobe. This video was super helpful!
Thank you for such a rock-solid answer!
Thanks David for the short and almost complete overview. The only link missing imho is the illuminated area. I couldn't find the standard for the measurement procedure and therefor assume that just the brightest spot is used for the marketing material. Comparing the flashes side by side seems like the only reliable possibility to get to the truth :)
Fantastic explanation 👏👍
Nice one David, got it! Thanks.
Great explanation, David.
Superb video. Thank you!
This was a great informative video. I got a lot out of this and Mark's video. I use a Godox TT685C and a Flashpoint Studio 400 monolight.
Thanks! Great info!!!
Always helpful David. Thank you! (I rarely use flash, since I shoot mainly wildlife and landscapes. But it's important to me at short ranges, for smaller items, macro, etc..) Thanks again for stopping by Ash's stream the other night. I know she appreciated it, and it was just generally nice to see a pro in there. Take care! :)
My pleasure!
Very helpful info... I really needs a good flash output but I've not been done for years. I know they had an excellent white balance on strobe tube. Had a hot tungsten lamps so many times but electric bill soars easily under high usage time and spending bulbs life quickly while working on the shot. 💡 Good time to get a flash gun before hot summertime and help keep a cool. I didn't want do hot light and box of fan at same time, that'll get high on electric bill otherwise it'll overloads on circuit breaker (once tripped). Evenly air conditioner (that'll do as well, too). 📸 Stay safe and healthy.
Very helpful. Thanks!
Very good information. I never understand this before. Thank you.
That was great David -- really was a great explanation of guide number. I use the 600 a lot, because I can go to a shoot with one light that is always enough. I shoot real estate and almost always bounce the light or shoot through an umbrella. You can never have enoughtlight.
When checking guide numbers for studio flashes, be sure to check what reflector they're using for the measurement! Different reflectors have different coverage, and some are simply more efficient. This can make a unit look 2 or more stops brighter' and give a guide number that's misleading when compared with other units which aren't.measured that way.
Got it! Awesome!
Thankyou David
Still using my SB800'S on my 850 and i use an SF60 on my Q twins.
Thanks David!!
How about taking out your speedlight and learning by shooting on you own at various ambient light, stops, power, modifier and lighting distance till you get it right. Won’t you eventually learn that if you need to lighten the subject by 2/3rds of a stop you will quickly know what settings are needed for that Speedlight.
Of course. As I say in the video, guide numbers won’t help much when you’re actually shooting. But for comparing strobes before you buy them, that number can be useful.
metric is used because there are 3 country in the world that work with the imperial system the U.S. is one of them of course Every other country in the world has adopted the metric system as the primary unit of measurement. that is why metric is used with the flash guides ect.
Yup. We should have switched a long time ago.
great videos
Berg knows everything
I did not even know that I needed to know this!
Now you know! 🤣
Are there any general guidelines on how modifiers reduce Guide Numbers? That would make an interesting video.
I do understand guide numbers were a good thing, but wow my head hurts!
Might take a couple views. :)
Nice video, David. The Guide Number informs me best how much light a flash puts out, but I immediately want to know the angle and ISO of the Guide Number (GN) and the length unit, as you said. Another detail I always want to know is the flash duration at full power.
Your Canon 600 does GN=60m, at ISO=100 and at a flash angle equal to a 200mm lens's angle. My Nikon SB-910 does GN=34 at ISO=100 for a 35mm lens and that is exactly what the Canon 600 does. I have 10 of these 910 speedlights, but also a couple SB-400 tiny cute 2xAA that can flip the reflector up or I can have them off camera on an i-TTL cable (or my PocketWizards). These little SB-400 are always on an angle covering a 28mm FX lens and at that have the same Guide Number as the SB-910 for 1/4 the price. The difference is in the Ampères that the bigger thing can handle and turn into fast recycle speeds, plus the adjustable flash angle and remote capabilities. Also, the SB-910 accepts an external power pack that triples the Ampères and makes it recycle much faster and at the same time you have many more flashes in reserve. I can easily "fill" a 1' x 4' (30x120) softbox with one of these, or even a 3' x 4' (90x120) albeit I will generally put two SB-910 in the latter to retain fast recycling.
Sounds like you’ve found the best setup for your shooting. Awesome!
@@DavidBergmanPhoto - it's not all "rose scent and moonlight" we'd say in my language, when it's not completely perfect. Recharging 10 * 12 AA batteries vacuums (*). And you need chargers that display individual cell health or else you really get sick & tired, and chargers that offer cell repair cycles. It's all very versatile, wireless, and powerful and fast enough, but doesn't have the proportional modeling light that my broncolor studio strobes had in "pro" 70s/80s. Had I started to buy my mobile studio a couple years later, then I probably had bought some serious Siros battery powered strobes to begin with.
(*) vacuum sucks
You are helping a lot. I just got a crown graphic with original flash and I want to use the #5 bulbs and I am trying to figure out correct exposure without using them all up. Any good suggestions would be appreciated.
I came from the Film era so it was really useful, today, everyone is trying to hide this spec, example the Xplorer 300 / Godox Ad300 Pro, I've not seen that spec not even on the Godox or Adorama site lol.
But I find it super useful because instead of taking the manufacturers numbers, I actually halve it, if I'm OK with that then, I'm OK getting what I'm shopping for. I know it's not an accurate way but my math especially once I try to factor in my diffusion get whacked 😂
I have a question: if the GN decreases, should we decrease it with zoom or flash so that the GN remains the same if the zoom is changed?
It’s interesting to know that Canon 600EX II-RT has nearly same GN as overhyped AD600😀
Great dose of knowledge, as always. But how does exposure calculated from GN correspond to incident light metering ? Is there any constant factor ?
Incident light is not a factor at all. The GN is just about the output from the flash only.
Excellent video! I did watch the Mark Wallace video ... also excellent. So, it’s been my experience that a “watt second” moniker from xyz company seems to imply you’re buying a better pro-type flash. Do all makers of flashes who trumpet their “watt seconds” also include Guide Number? Is the GN is very small print? :-)
i was wondering what type of lens would be best to photograph a giraffe on a trampoline?
would i go with a wide angle lens for the low shots as it comes back down or use a telephoto for the long shot when its up in the air?
Personally I’d go long lens so the giraffe doesn’t land on my head! 🤣
Link to the other video Mr. Bergman referenced?
It’s in the description, but I’ll post it here too: th-cam.com/video/E-ro-ST3iuo/w-d-xo.html
Also, Mr. Bergman was my father. You can call me David. 🤘