Guide numbers - how to work out which flash has a better output

[Tan Tan]

Hello
I have always used Canon 580's off camera for portraits on the go .
They work fine for my needs , but I only have 2 left and know they wont last forever

I have recently purchased a Godox V1 pro and would like more for fill and backlight . I prefer using the same type of flashes

Question ....Does a Godox V1 Pro have more output than a 580 or do I need to move to an AD 200

I know a Canon 580 has a guide no. of 58 but cant find info on the Godox

TIA

 

[thomste]

Hello
I have always used Canon 580's off camera for portraits on the go .
They work fine for my needs , but I only have 2 left and know they wont last forever
I have recently purchased a Godox V1 pro and would like more for fill and backlight . I prefer using the same type of flashes
Question ....Does a Godox V1 Pro have more output than a 580 or do I need to move to an AD 200
I know a Canon 580 has a guide no. of 58 but cant find info on the Godox
TIA

According to Godox the V1 has a GN of 28 meters.
the AD200 is 60 meters

 

[Tan Tan]

Wow so my ancient canon 580s had a guide no. Of 58

so

would that mean they are still more powerful than a modern Godox V1 Pro ?

Is that how it works ?

 

[thomste]

Wow so my ancient canon 580s had a guide no. Of 58

so

would that mean they are still more powerful than a modern Godox V1 Pro ?

Is that how it works ?

The V1 has a round head so it probably makes a difference to how the light travels.
28 meters is plenty though

 

[Gato Amarillo]

Guide numbers are tricky, especially for a flash with a zoom head where the guide number varies with the zoom setting.

If I read your post correctly you have both flashes. It should be easy to set up test shots to see how they compare. That will likely tell you more than just looking at guide numbers.

Gato

 

[Tan Tan]

Thanks , yes I have both .

Ill have to try , I would have like to have thought the newer Godox one had more power than a 15yr old flash

many thanks

 

[Gato Amarillo]

Digging a little more and looking at the electrical power, the V1 is rated at 76 watt seconds, while the 580 is estimated to be around 70 WS. So in terms of pure power the V1 is a bit more powerful, but not a lot.

However the zoom on the 580 lets you concentrate the light into a narrower beam, so it can put more light on a small area. The 58 guide number is at the 105mm zoom setting, so a fairly narrow beam. The V1 spreads the light over a much larger area, so you would have to zoom back the 580 to get a fair comparison.

So, if you are using your 580 at a longish zoom setting it will put more light on the subject, but in a narrow area. If you pull back the zoom to cover the same area as the V1 they will be much closer.

Just to note, I'm writing this at 3 in the morning after taking cold medicine. I hope it makes sense.

Gato

 

[Tan Tan]

Yes it makes sense and I appreciate the follow up

hope you feel better

thank you

 

[tugwilson]

Guide numbers are a terrible measure of the "power" of a zoomable light as it measures two things at once i.e. the light output and the ability of the light to concentrate that light.

As you own the V1Pro and the 580 you can answer that question yourself by simple experiment.

The V1Pro is a bit of a strange choice to replace a 580 used off camera. The V1Pro is a perfectly good device it's basically a V1 with enhancements that allow it to support about twice the number of rapid pops before overheat protection cuts in. As side effect of that HSS performance is significantly improved. If one or both of these are important to you then it's a very worthwhile investment. If not you are probably better off with a V1.

If you are only going to use the lights off camera then the AS100Pro is a better bet than the V1/V1Pro

 

[Tan Tan]

Thank-you for yr reply much appreciated

Why is it a strange choice replacing a 580 with a V1 Pro ?

my 580s we’re all dieing as they are so old . I’m using 1DXs so I could only see the Godox V1 Pro as a replacement

newer canon flashes are not compatible with the 1DX s

kind Regards

 

[thomste]

Thank-you for yr reply much appreciated

Why is it a strange choice replacing a 580 with a V1 Pro ?
my 580s we’re all dieing as they are so old . I’m using 1DXs so I could only see the Godox V1 Pro as a replacement

newer canon flashes are not compatible with the 1DX s

kind Regards

Godox also has the TT685 model, which is more of a 'normal' speedlight than the V1

 

[Tan Tan]

Thankyou ,
not one of the major camera stores in Australia mentioned the TT6685 as being an option when i was looking . Thanks for your help

 

[tugwilson]

Thank-you for yr reply much appreciated

Why is it a strange choice replacing a 580 with a V1 Pro ?
my 580s we’re all dieing as they are so old . I’m using 1DXs so I could only see the Godox V1 Pro as a replacement

I thought I'd explained that in the post.

The V1Pro is a higher priced version of the V1 designed for people who want to fire lots of rapid pops. E.G. Paparazzi style event photographers using it on camera. If you only want to use off camera flash the AD100Pro is cheaper, more powerful and easier to set up than the V1Pro.

 

[Tan Tan]

many thanks for your reply

 

[tugwilson]

Thankyou ,
not one of the major camera stores in Australia mentioned the TT6685 as being an option when i was looking . Thanks for your help

You might find this listing of all the Godox conventional speedlights helpful. Devices with a V prefix have Li-Ion batteries the TT prefix use AA batteries. If you ignore the 350 speedlights they are all pretty much the same power. They differ in the shape of the head and support for TTL. The devices that have camera brand specific versions support TTL and HSS on and off camera the others don't support TTL at all and only support HSS off camera.

My favorite is the TT600 which costs ~£65

 

[BAK CDN]

As I type this, you've received about a dozen replies.

This message from me speaks to the question of whether you should buy a couple more V1 Pro flash units, or a couple of AD200 flash units, or some other flash units, to provide additional fill, background light, big room coverage, etc.

BUDGET: My comments below are based on mid-range budgets. No Profoto. No cheap Chinese nameless flashes or Amazon specials.

GUIDE NUMBERS: Thses are complicated and confusing, because there are many different guide numbers for each flash, depending on ISO and angle of the flash. So to compare guide numbers supplied by manufacturers, You need to know what parameters they used to calculate what they say. i.e. one number may be based on ISO 100 and 50mm coverage (the old standard) and another flash unit based on ISO 400 at 200mm coverage.

The guide numbers are calculated for distance in feet, and distance in meters. The difference in numbers is simply multiplying or dividing by 3. A 110 feet guide number is a 40 meter guide number. (3 x 40 is 120, which is close enough to 110 to work)

AN ASIDE: To use a guide number when the flash is pointed toward the subject, divide the guide number by the distance to the subject and set the result as your aperture.

An Imperial guide number of 110 divided by a 10 foot distance is f/11.

POWER REQUIRED: It is very rare that a photographer "needs" maximum power. You can move the flash closer, or open the aperture or increase the ISO or wait a second or two longer between shots to allow fuller recharging. Or change a light modifyer; replace a whie umbrells with a silver one, for instance.

That said, more power means smaller aperures and lower ISOs mean (maybe, but it is hard to tell) better picture quality. Smaller apertures meaaan greater depth of field, as long as you have enough lighting units to evenly illuminate the whold scene.

FLASH UNIT SHAPE: There are currently tow main styles. The speedlight, which fits easily on top of the camera or on a lightstand, and has a head that bends and twists. The V1Pro in your case. Most speedlights are battery-power, and lithium batteries are great/

And the monolight, which may be powered from a wall or by, in some cases battery, and does not fit easily on top of the camera. The AD100 Tug mentioned is a great, small, powerful enough usually, battery powered monolight that usually needs a stand.

YOU DECIDE: There are advantages to both styles. The AD200 is sort of a hybrid.

ME: I use ol;d wall-powered Dynalite pack-and-head systems, and to Godox speedlights. Next purchase will probably be a Godox AD100.

BAK

 

[Jacques Cornell]

Digging a little more and looking at the electrical power, the V1 is rated at 76 watt seconds, while the 580 is estimated to be around 70 WS. So in terms of pure power the V1 is a bit more powerful, but not a lot.

However the zoom on the 580 lets you concentrate the light into a narrower beam, so it can put more light on a small area. The 58 guide number is at the 105mm zoom setting, so a fairly narrow beam. The V1 spreads the light over a much larger area, so you would have to zoom back the 580 to get a fair comparison.

So, if you are using your 580 at a longish zoom setting it will put more light on the subject, but in a narrow area. If you pull back the zoom to cover the same area as the V1 they will be much closer.

The V1 also zooms to 105mm coverage.

Just to note, I'm writing this at 3 in the morning after taking cold medicine. I hope it makes sense.

Gato

 

[Jacques Cornell]

30-40 years ago, before a lot of flashes had zooming heads, guide numbers were useful because almost all flash makers published specs based on coverage of the Field of View of a 35mm lens on a 35mm-format camera. So, comparisons were roughly apples to apples.

Nowadays, guide numbers are mostly meaningless, as the parameters for measurement are all over the place.

For your purposes, though, that's OK, because a rough rule of thumb is really all you need. First, consider all "full-size" speedlights essentially the same in terms of output power. They all produce roughly 70-80WS. Smaller ones, like Canon's 420, might be around 50-60WS, and even smaller ones, such as Godox' TT350/V350, might be 40WS. I haven't measured these or even compared the output of my TT350, V860III and V1, because I know from experience what each can do. Going the other direction, an AD100 produces probably 1/3 of a stop more light than a full-size speedlight, and an AD200 is probably 1-1/3 stops brighter than said speedlight. The differences in output among units of a particular class are likely negligible in practical terms. In your case, a TT685, V850/V860 or V1 will all serve pretty much the same purposes as your Canon 580.

If you want another EV or so more light than your 580 delivers, maybe for filling a decent-size octa, Godox' AD200 is a pretty obvious and popular choice. If you need another stop you can combine two AD200s in an AD-B2 bracket for a 400WS light. Next stop up the ladder, IMHO, would be an AD600 variant.

 

[Gato Amarillo]

Digging a little more and looking at the electrical power, the V1 is rated at 76 watt seconds, while the 580 is estimated to be around 70 WS. So in terms of pure power the V1 is a bit more powerful, but not a lot.

However the zoom on the 580 lets you concentrate the light into a narrower beam, so it can put more light on a small area. The 58 guide number is at the 105mm zoom setting, so a fairly narrow beam. The V1 spreads the light over a much larger area, so you would have to zoom back the 580 to get a fair comparison.

So, if you are using your 580 at a longish zoom setting it will put more light on the subject, but in a narrow area. If you pull back the zoom to cover the same area as the V1 they will be much closer.

The V1 also zooms to 105mm coverage.

Just to note, I'm writing this at 3 in the morning after taking cold medicine. I hope it makes sense.

Gato

My mistake - did not know the V1 had zoom. Thanks for the correction.

In that case the OP would want to compare them at the same zoom setting.

G

 

[Tan Tan]

Thanks for that , yes yr absolutely right about the guide no.s being measured differently

I guess I was trying to compare the power of each flash by the guide no. their manufacturer provided .

i was assuming the guide nos given were calculated the same way and wanted to know where the V1 pros sat compared to the old 580s I have

I mainly shoot events with the flash on top of camera ..I also shoot portraits and products on location where I use 2 or 3 flashes (on stands ) shooting through umberellas

Thankyou for yr time