Nikon SB800/900 real GN value ...

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Arnaud M
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Nikon SB800/900 real GN value ...
5 months ago

Does someone has made real power measurements with a flash meter of the Nikon Speedlight SB900 and SB800 ?

I have been testing my side last night with a Sekonic 308s which seems to confirm my observations in the field.

I find a guide number of 22.9 at full power flashes wathever the model powered by 4 x 1.5V alcalynes batteries or 4 x 1.2V Eneloop batteries.
Flash set to manual at full power, FX format on SB900, 35mm manual focal length, flash meter to 1 meter in line with the flash in a dark room with little stray reflections, ISO 100.

Feeding the SB800 with 5 alcalynes 1.5V batteries, the guide number changes to 32.1

We are far from the values ​​announced by Nikon SB900 (GN 34 @ 35mm FX).

Is this due to the aging of the flash tube or can you confirm these values ​​?

Thank you for your contribution.

Arnaud Marie
France
http://arnaudmarie.zenfolio.com

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Ferguson
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

Is this due to the aging of the flash tube or can you confirm these values ​​?

I have neither flash meter nor SB900, but I had two SB8800's on my desk coming back from a shoot today. One has a brand new flash tube (at least Nikon said they swapped it), one a tube about 8-10 years old.

I broke out the manual and looked up the 50mm guide number (144 (feet) at 100 ISO) and measured off a wall 12 feet away. I did three exposures in a dark room - one at F13 (ok, not quite F12) with each flash on M1/1, and one with TTL. The histogram was identical on the two manual and just ever so slightly less bright on the TTL shot. All three looked correctly exposed (perhaps a tad over exposed, as the 12' was to a corner and the walls were closer).

Not scientific, but the guide number seemed to work in that regard, and the old/new had no apparent difference.

Both were with five NiMH LSD batteries, each probably about 60-80% charge based on shooting about 100 medium power shots today.

Sorry I can't help with the science, but the "gut check" says it all aligns for the SB800.

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michaeladawson
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

Does someone has made real power measurements with a flash meter of the Nikon Speedlight SB900 and SB800 ?

I have been testing my side last night with a Sekonic 308s which seems to confirm my observations in the field.

I find a guide number of 22.9 at full power flashes wathever the model powered by 4 x 1.5V alcalynes batteries or 4 x 1.2V Eneloop batteries.
Flash set to manual at full power, FX format on SB900, 35mm manual focal length, flash meter to 1 meter in line with the flash in a dark room with little stray reflections, ISO 100.

Feeding the SB800 with 5 alcalynes 1.5V batteries, the guide number changes to 32.1

There should be no increase in GN due to putting in an extra battery.  The power to the flash is provided by the capacitor.  A 5th battery should only serve to recharge the capacitor faster and to provide more total flashes off a set of batteries.

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Arnaud M
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Re: Nikon SB800/900 real GN value ...
In reply to michaeladawson, 5 months ago

Ok, I made ​​a mistake in my first post. The guide number does not change with 5 battery and remains at 22.9.

No one else has made a test with a flash meter ?

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olyflyer
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I have never measured the real GN value ...
In reply to Arnaud M, 5 months ago

...but if I have time this weekend I might do it. I have the SB-900 and a light meter, so that's not an issue. When you measured the light, did you have the diffuser dome over the light sensor of your meter, or was it off to the side? I think that it must be off for this type of measurement, since all you want to know is the maximum light, so it must not be defused.

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Arnaud M
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Re: I have never measured the real GN value ...
In reply to olyflyer, 5 months ago

According to the flashmeter manual, it must be use with the diffuser in place.

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SVPhotography
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Re: I have never measured the real GN value ...
In reply to Arnaud M, 5 months ago

I don't know about the SB-900 but on the SB-800, if you stick the diffuser on - you will never get the flash head to zoom to 35mm....

I am pretty sure that the GN number was measured without the diffuser in place - especially if it stated at 35mm FX because the only way to zoom the head is to remove the diffuser.

Arnaud M wrote:

According to the flashmeter manual, it must be use with the diffuser in place.

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elliotn
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

Ok, I made ​​a mistake in my first post. The guide number does not change with 5 battery and remains at 22.9.

No one else has made a test with a flash meter ?

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I just tried with an SB80DX (same GN as SB800?) and a Sekonic light meter.

At 35mm I read f22.7

At 105mm I read f32.4

I can't see much to be concerned about.

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Arnaud M
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Re: I have never measured the real GN value ...
In reply to SVPhotography, 5 months ago

SVPhotography wrote:

I don't know about the SB-900 but on the SB-800, if you stick the diffuser on - you will never get the flash head to zoom to 35mm....

I am pretty sure that the GN number was measured without the diffuser in place - especially if it stated at 35mm FX because the only way to zoom the head is to remove the diffuser.

Arnaud M wrote:

According to the flashmeter manual, it must be use with the diffuser in place.

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We were talking about the sekonic dome diffuser for incidence light mesurement, not the flash diffuser !

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Arnaud M
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Re: Nikon SB800/900 real GN value ...
In reply to elliotn, 5 months ago

elliotn wrote:

Arnaud M wrote:

Ok, I made ​​a mistake in my first post. The guide number does not change with 5 battery and remains at 22.9.

No one else has made a test with a flash meter ?

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I just tried with an SB80DX (same GN as SB800?) and a Sekonic light meter.

At 35mm I read f22.7

At 105mm I read f32.4

I can't see much to be concerned about.

The guide number of the sb80dx is 38 !!!

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StillLearning
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

I did a similiar test with the SB-800 many years ago when I was comparing my Photogenic monolight.  I was testing in Feet and and was at 10 feet distance.  Found the SB-800 to be about 15% less than specified.  My Monolight was 5 % more.  I also noticed if I went to 5 feet my reading
went lower.  Try 2 meters and 3 meters and see if it remains the same or changes.

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elliotn
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

elliotn wrote:

Arnaud M wrote:

Ok, I made ​​a mistake in my first post. The guide number does not change with 5 battery and remains at 22.9.

No one else has made a test with a flash meter ?

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I just tried with an SB80DX (same GN as SB800?) and a Sekonic light meter.

At 35mm I read f22.7

At 105mm I read f32.4

I can't see much to be concerned about.

The guide number of the sb80dx is 38 !!!

Ok, so it's two thirds of a stop underpowered. Not a big deal for me.

I have four SB80DXs (different vintages, purchased on ebay), and they all meter exactly the same.

It's been a long time since I used guide numbers for anything - or my Sekonic meter, for that matter.

I use the SB80s all the time, but normally off-camera, at low power (1/4 or less), to mix with ambient.

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olyflyer
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Re: I have never measured the real GN value ...
In reply to SVPhotography, 5 months ago

SVPhotography wrote:

I dolightw about the SB-900 but on the SB-800, if you stick the diffuser on - you will never get the flash head to zoom to 35mm....

I am pretty sure that the GN number was measured without the diffuser in place - especially if it stated at 35mm FX because the only way to zoom the head is to remove the diffuser.

It is the diffuser of the light meter I am talking about. Not the flash.

Arnaud M wrote:

According to the flashmeter manual, it must be use with the diffuser in place.

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olyflyer
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Re: I have never measured the real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

According to the flashmeter manual, it must be use with the diffuser in place.

I didn't know the manual described how to measure the GN. I would do it without.

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Arnaud M
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Re: I have never measured the real GN value ...
In reply to olyflyer, 5 months ago

It-s not a specific way to measure the GN, it's just the way to use the incident light meters.

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elliotn
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Re: I have never measured the real GN value ...
In reply to olyflyer, 5 months ago

olyflyer wrote:

...but if I have time this weekend I might do it. I have the SB-900 and a light meter, so that's not an issue. When you measured the light, did you have the diffuser dome over the light sensor of your meter, or was it off to the side? I think that it must be off for this type of measurement, since all you want to know is the maximum light, so it must not be defused.

That's all wrong. The light meter's diffuser must be in place.

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olyflyer
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Re: I have never measured the real GN value ...
In reply to elliotn, 5 months ago

elliotn wrote:

olyflyer wrote:

...but if I have time this weekend I might do it. I have the SB-900 and a light meter, so that's not an issue. When you measured the light, did you have the diffuser dome over the light sensor of your meter, or was it off to the side? I think that it must be off for this type of measurement, since all you want to know is the maximum light, so it must not be defused.

That's all wrong. The light meter's diffuser must be in place.

That depends... did you understand what we are discussing here?

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olyflyer
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Re: I have never measured the real GN value ...
In reply to Arnaud M, 5 months ago

Arnaud M wrote:

It-s not a specific way to measure the GN, it's just the way to use the incident light meters.

Yes, when you want to take images. I know that very well, but I am not so sure it is the same as measuring the maximum output from the flash. Did you try both ways?

I just checked the manual, and it does not describe how to measure flash output, so I guess we are in the blind here.

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Ferguson
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Re: I have never measured the real GN value ...
In reply to olyflyer, 5 months ago

olyflyer wrote:

Arnaud M wrote:

It-s not a specific way to measure the GN, it's just the way to use the incident light meters.

Yes, when you want to take images. I know that very well, but I am not so sure it is the same as measuring the maximum output from the flash. Did you try both ways?

I just checked the manual, and it does not describe how to measure flash output, so I guess we are in the blind here.

If you want to confirm your measurement of guide numbers, I'd suggest something more controlled but like I did -- a specific lens and distance, a grey card if you have one, get a camera-measured-non-flash shot of it so you know the specific converted value of that grey card, and compare to the flash-output-only value of that grey card when exposed according to the guide number.  In something like lightroom you can then see how many stops (or fraction) you need to raise or lower it to match the camera's "right" exposure.

If it comes out correct, then the output matches the guide number, regardless of what the light meter says.

Or conversely, if they match, you'll have evidence that the technique you're using is either right, or off the same amount as the flash.  

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snellius
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Re: Nikon SB800/900 real GN value ...
In reply to Arnaud M, 5 months ago

How did you measure the distance? At 1 meter from the front of the flash, or the shooting distance of 1 m (distance to the film or sensor). At 1 meter, this can be a big difference. At 5 meters it does not matter anymore. The guide number is also based on an average amount of reflection.

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