Nikon SB 800 vs Sekonic L558

Ardpatrick · Aug 1, 2024

I recently acquired a used Nikon SB800 speedlight in decent condition, for use with various film cameras for fill lighting etc. I wanted this particular model because it’s widely compatible with analog & digital Nikon gear.

I’m currently testing it by using it in manual mode at various power settings (1/8, 1/16, 1/32 etc), various zoom settings, specified apertures, and specified distances, as determined by the unit itself and displayed on its rear LCD screen. I’ve carefully measured out the specified range for a given setting, and carefully placed my Selonic L558 at the the exact measured distance. In incident mode (dome up and directly addressing the flash) and cordless flash metering, I’ve measured the actual output of the SB 800.

Over a dozen tests, using various settings, and also repeating the same settings too to verify consistency, I always end up with 1/2 to 1.3 stops of under exposure. When the flash tells me I can set my lens to f.11 the light meter says I need f.8 for example. At least according to the Sekonic meter.

It’s not the end of the world and even with a weaker than supposed output the flash has plenty of power. But the underexpose is not equal across the range, which makes any simple compensation complicated. I could plot it out but I’d much prefer to have the flash as a quick and convenient tool rather than one that requires me to break out the calculator for every shot.

Finally to clarify - No camera was required nor used in the test. The SB 800 was fired using the rear “Test” button. No metering was involved EXCEPT for the Sekonic, which measured the exposure at the range distance. I tested the flash in manual mode precisely because I wanted to by-pass any TTL / Auto influence on the flash output.

I’m interested in any suggestions around the discrepancy between the flash LCD exposure recommendation and the measured exposure at the range distance. I’m also interested in any other techniques for establishing the actual flash output. Of course the issue might be the sekonic meter is inaccurate, which is almost as old as the flash gun (approx. 20 years). - but I have had the meter 20 years and I totally trust it. Thoughts?

Ardpatrick · Aug 1, 2024

Ps. One explanation could be that the particular unit of used SB 800 I acquired, may not deliver as much actual light output as it did 20 years back when it was manufactured. Is that likely? Do flash guns & heads change output over time etc?

chriscrawfordphoto · Aug 1, 2024

Ardpatrick said:
Ps. One explanation could be that the particular unit of used SB 800 I acquired, may not deliver as much actual light output as it did 20 years back when it was manufactured. Is that likely? Do flash guns & heads change output over time etc?

Yes, they can become weaker as they age, especially if used heavily in the past. Test by taking actual pictures; I bet the Sekonic will be right. If you have a Nikon camera with TTL auto flash exposure, it should be right, too (when shooting in auto mode) since it measures actual flash output just like the Sekonic does.

Nitroplait · Aug 1, 2024

chriscrawfordphoto said:
If you have a Nikon camera with TTL auto flash exposure, it should be right

+1
If used with a TTL camera, a flash output variation should be of no consequence.

If you fire the flash in manual mode with a digital camera adjusted manually to the setting suggested by flashmeter or flash, you should quickly be able to see which is closer to the truth.

Ardpatrick · Aug 1, 2024

chriscrawfordphoto said:
Yes, they can become weaker as they age, especially if used heavily in the past. Test by taking actual pictures; I bet the Sekonic will be right. If you have a Nikon camera with TTL auto flash exposure, it should be right, too (when shooting in auto mode) since it measures actual flash output just like the Sekonic does.

Thanks to all for the collective perspective. Interesting to hear confirmation that the actual output of these units diminishes over time. Now I somewhat regret not springing for the ‘mint’ condition offers from Japan now when purchasing.

It’s not the output itself that’s a problem but the disparity between what the display claims and what the flashmeter registers. I’m well aware of GN numbers and have verified real world GN numbers before, but I don’t want to have to calculate using GN numbers when I’m quickly looking for fill flash when shooting quickly with my Mamiya 7. I want something easy. Still if the auto thryistor function still works I should be able to use the unit for my purposes. I like the flash a lot.

Sharktooth · Aug 1, 2024

Your tests with the flash and meter haven't really achieved anything useful, other than proving that flash makers always exaggerate their output ratings. It's the same thing as car makers exaggerating their mpg ratings.

Power output is important if you're using the flash in manual mode, and have no way to meter. In reality, nobody would do that with a modern camera mounted flash.

The control system in a Nikon SB00 flash unit is very sophisticated. The simplest mode is A mode, where a sensor in the flash measures the light reflected from the subject, and cuts the flash output when the optimum exposure is received. Other modes combine the camera sensors and preflashes to determine flash exposure duration. This sophistication makes them very good for fill flash exposure in dynamically changing light, which is your desired goal. There's no way to do this practically with a manual only flash.

Just do some practical tests in the type of lighting you expect to be using. A handheld flash meter is great for use in the studio, where the lighting isn't changing rapidly, but isn't going to help you with fill flash in dynamic lighting situations.

Chan Tran · Aug 1, 2024

First of all retract the dome. GN should be tested with the dome retracted. However, if you find less than 1 stop under the flash is normal. I found most flashes put out about 1 stop less light than the GN said. It's not because the flash got weaker as it's older. I have tested flashes of many brands Metz, Nikon, Vivitar, Sunpak, Rollei etc.. and all of them produced less light than the specs.

Ardpatrick · Aug 1, 2024

Sharktooth said:
Your tests with the flash and meter haven't really achieved anything useful, other than proving that flash makers always exaggerate their output ratings. It's the same thing as car makers exaggerating their mpg ratings.

Power output is important if you're using the flash in manual mode, and have no way to meter. In reality, nobody would do that with a modern camera mounted flash.

The control system in a Nikon SB00 flash unit is very sophisticated. The simplest mode is A mode, where a sensor in the flash measures the light reflected from the subject, and cuts the flash output when the optimum exposure is received. Other modes combine the camera sensors and preflashes to determine flash exposure duration. This sophistication makes them very good for fill flash exposure in dynamically changing light, which is your desired goal. There's no way to do this practically with a manual only flash.

Just do some practical tests in the type of lighting you expect to be using. A handheld flash meter is great for use in the studio, where the lighting isn't changing rapidly, but isn't going to help you with fill flash in dynamic lighting situations.

Well I’ve learned that I can’t trust the LCD guide on the rear of the flash! I think that’s useful to know. If I go to the trouble of plotting the disparity at different manual settings & zoom settings between LCD info and actual measured results, that could also be useful in the field, albeit far less convenient than I’d like.

But hopefully the auto mode which should be independent of manufacturers inflated GN claims, is fairly reliable!

Ardpatrick · Aug 1, 2024

Chan Tran said:
First of all retract the dome. GN should be tested with the dome retracted. However, if you find less than 1 stop under the flash is normal. I found most flashes put out about 1 stop less light than the GN said. It's not because the flash got weaker as it's older. I have tested flashes of many brands Metz, Nikon, Vivitar, Sunpak, Rollei etc.. and all of them produced less light than the specs.

Retract the dome? Interesting point. I can see why that would be more accurate for measuring GN, but I’m actually interested in measuring exposure rather than GN. In real world situations I’ve always measured incidence with the dome protruding unless doing copy work or lighting ratios.

And surely having the dome protruding would increase exposure due to increased sensitivity to peripherally reflected light. My issue thus far is under-exposure.

Ardpatrick · Aug 1, 2024

Chan Tran said:
First of all retract the dome. GN should be tested with the dome retracted. However, if you find less than 1 stop under the flash is normal. I found most flashes put out about 1 stop less light than the GN said. It's not because the flash got weaker as it's older. I have tested flashes of many brands Metz, Nikon, Vivitar, Sunpak, Rollei etc.. and all of them produced less light than the specs.

Also thanks for sharing your experience with a variety of different units. I have a couple of old Vivitars with clunky sliding scales on the rear etc and yes their measured GN is significantly lower than the manual claims. I guess I just expected a little more accuracy from the rear LCD of a “pro” flash like the Nikon SB-800.

Ardpatrick · Aug 1, 2024

Ardpatrick said:
Also thanks for sharing your experience with a variety of different units. I have a couple of old Vivitars with clunky sliding scales on the rear etc and yes their measured GN is significantly lower than the manual claims. I guess I just expected a little more accuracy from the rear LCD of a “pro” flash like the Nikon SB-800.

I also have a modern Godox 860 (something or other) unit that I use with a Dslr. I’m curious if that also under delivers!

Chan Tran · Aug 1, 2024

Ardpatrick said:
I also have a modern Godox 860 (something or other) unit that I use with a Dslr. I’m curious if that also under delivers!

I am curious too because so far I have found no flash that met the claimed GN rating.

MattKing · Aug 1, 2024

GN ratings almost always include assumptions about reflectance from surrounding surfaces such as ceilings and floors, so they are by nature estimates.
Those assumptions are viable, because light reflecting off those surfaces does matter and ignoring them can result in over-exposure.
But yes, they are often at least a bit optimistic.

Chan Tran · Aug 1, 2024

MattKing said:
GN ratings almost always include assumptions about reflectance from surrounding surfaces such as ceilings and floors, so they are by nature estimates.
Those assumptions are viable, because light reflecting off those surfaces does matter and ignoring them can result in over-exposure.
But yes, they are often at least a bit optimistic.

I read somewhere a document from Metz about testing the GN but I couldn't find it now. They said using a 50% reflectance surface and make a reflected light measurement from it.

MattKing · Aug 1, 2024

Chan Tran said:
I read somewhere a document from Metz about testing the GN but I couldn't find it now. They said using a 50% reflectance surface and make a reflected light measurement from it.

That is the measurement, but the actual calculation of the level of illumination from the flash assumes use in something like a living room with walls and ceilings available to reflect some light on to the subject.
The classic issue was when someone tried to use Guide Numbers with flash bulbs or manual flashes in hotel ballrooms (high ceilings, dark floors, and no nearby walls) when photographing the bride and groom during their first dance . Those shots would come out under-exposed unless the lack of reflecting surfaces was compensated for.

Ardpatrick · Aug 1, 2024

For what it’s worth my tests were carried out in an average sized living room of an older style house - white-ish ceiling about 8-9 feet high, dark wooden floor, and pale walls covered with plenty of photos & bookshelves. Fairly ‘average’ and I chose the room with that in mind. I used 50mm / 70mm zoom settings at about a 14 ft (3.5M) range. It doesn’t have the environmental reflectance of an art gallery, but it’s hardly abnormal.

Ultimately the acid test will be testing the auto mode to see how accurate the range / aperture guide on that LCD is. If the flash LCD tells me it can provide enough output for me to expose a scene at f.8 at a given distance, I need to know I’ll get correct exposure on film from the flash.

In that regard, what’s the optimal testing environment? The auto thriystor meter is reflective, whereas I’m using the Sekonic in incident mode (spot is an option too). Short of an 18% grey room what to look for?

MattKing · Aug 1, 2024

I used to gauge the reflectance of my subject by looking at it and making an educated guess. I would then incorporate the guess into my camera settings.
With Vericolour or Portra negative films, and either Vivitar or Metz automatic "thyristor" flashes, I was very happy with my auto-flash exposures. The test functions on the flashes were reliable.

Chan Tran · Aug 1, 2024

Ardpatrick said:
For what it’s worth my tests were carried out in an average sized living room of an older style house - white-ish ceiling about 8-9 feet high, dark wooden floor, and pale walls covered with plenty of photos & bookshelves. Fairly ‘average’ and I chose the room with that in mind. I used 50mm / 70mm zoom settings at about a 14 ft (3.5M) range. It doesn’t have the environmental reflectance of an art gallery, but it’s hardly abnormal.

Ultimately the acid test will be testing the auto mode to see how accurate the range / aperture guide on that LCD is. If the flash LCD tells me it can provide enough output for me to expose a scene at f.8 at a given distance, I need to know I’ll get correct exposure on film from the flash.

In that regard, what’s the optimal testing environment? The auto thriystor meter is reflective, whereas I’m using the Sekonic in incident mode (spot is an option too). Short of an 18% grey room what to look for?

use the Sekonic in spot mode and make sure the on flash sensor see a blank wall or something of the same color thru out. But I also find for most flashes the auto is quite accurate and thus at the limit on the scale the flash will often indicates under exposure that is the OK light won't light up. So my conclusion that flash manufacturers over state their published GN.

benveniste · Aug 1, 2024

Ardpatrick said:
Over a dozen tests, using various settings, and also repeating the same settings too to verify consistency, I always end up with 1/2 to 1.3 stops of under exposure. When the flash tells me I can set my lens to f.11 the light meter says I need f.8 for example. At least according to the Sekonic meter.

What zoom setting do you have the SB-800 set at?

Ardpatrick · Aug 1, 2024

benveniste said:
What zoom setting do you have the SB-800 set at?

50-70mm

Sharktooth · Aug 1, 2024

Modern flash units like the Nikon SB800 are designed to be used in a closed loop system. There is a computer in the camera that communicates with the flash, and controls its output. Modern cameras have multiple flash sensors in the camera that feed information to that computer. The computer also gets information about subject distance from the autofocus system. All of this is designed to calculate good exposure in microseconds, without the user needing to do any of these calculations manually. Using one of these flash units in manual mode makes no sense, unless you have a very specific application that needs it. In that case, a suitable hand held meter would be appropriate.

The Nikon SB800 offers a manual mode, since they've had a long history of supporting their older cameras and technology, and also for times when someone might want to use one of these flashes in a studio setting/fixed environment. If you're using manual mode, then you should be using a handheld meter anyway, so there's no need for them to invest a lot of time and money to develop a "dumb" manual system.

The A mode (automatic mode) is a throwback to the 1970's. These flash units had a single light sensor to read the reflected flash light, and a basic microprocessor to cut the flash when the appropriate exposure was achieved. The camera is not involved in any of this, except to trigger the flash. The A mode is therefore useful for older cameras that don't have any internal flash metering capability (1970's and older), The disadvantage of these flash units is that the single metering cell has all the same limitations as a single cell ambient meter in the camera. It just gives an average reading, and has no way to account for the type of subject matter.

Once you get into the mid/late 1980's and newer, matrix metering is now extended to the flash metering system. The Nikon F5, for example, has 5 cells to read flash, so it's much better at analyzing a scene than any singe cell metering system.

Bottom line, stop worrying about the flash to meter comparison, since it's meaningless for the actual usage of the flash.

For your older film cameras, use the flash mode that suits the camera. Use A mode for cameras that don't have any internal flash metering capability. When using the flash with those cameras, be aware that you've only got a single averaging meter in the flash unit, and all the drawback that implies.

Most of the autofocusing Nikons will have some type of flash controller in the camera, so use the appropriate mode for the camera.

If you're using the SB800 in a studio or other fixed setting, and off the camera, then just use your Sekonic to determine the appropriate exposure.

Chan Tran · Aug 1, 2024

Sharktooth said:
Bottom line, stop worrying about the flash to meter comparison, since it's meaningless for the actual usage of the flash.

Bottom line is that the flash capability is less than what the manufacturer claimed. When you need the power it's not there. I have 10ft ceiling and the SB-800 or SB-900 or most shoe mount flash can't do a celing bounce at f/5.6 @ISO100.

RalphLambrecht · Aug 1, 2024

Chan Tran said:
First of all retract the dome. GN should be tested with the dome retracted. However, if you find less than 1 stop under the flash is normal. I found most flashes put out about 1 stop less light than the GN said. It's not because the flash got weaker as it's older. I have tested flashes of many brands Metz, Nikon, Vivitar, Sunpak, Rollei etc.. and all of them produced less light than the specs.

Bingo. te capacitor of a 20-year-old flashgun is likely to have decreased in power. One way to full capacity is 'exercise it multiple times at full power and test it again. If that doesn't help, it may be time for a new one or live with it as is.

Sharktooth · Aug 1, 2024

Chan Tran said:
Bottom line is that the flash capability is less than what the manufacturer claimed. When you need the power it's not there. I have 10ft ceiling and the SB-800 or SB-900 or most shoe mount flash can't do a celing bounce at f/5.6 @ISO100.

You're missing the point, Chan. I fully agree that the manufacturers claimed output is overstated. That's what I said in my original post.

The bottom line is that it doesn't really matter for practical purposes.

There are really only three ways to determine exposure:

1) A handheld flash meter (like the Sekonic)
2) A flash metering system in the camera and/or flash
3) A manual calculation based on actual flash output.

Knowing the actual flash output is only useful in method 3, where you need to do a manual calculation to determine exposure, based on camera to subject distance. In your example with a ceiling bounce, you could use method 1 with a handheld flash meter at the subject to determine exposure. You could also rely on the reflected light measurement from the camera/flash system, as in method 2. Both methods 1 and 2 should indicate underexposure if there's not enough light. Method 2 would be fast and easy, while method 1 could be somewhat inconvenient, depending on the situation.
That leaves method 3. You could take your known flash output, and then measure the distance from the flash to the ceiling. With that you'd have to estimate the reflectance value of the ceiling and determine how much light loss is at the ceiling. After that you'd have to measure the distance from the ceiling to the subject, and then calculate the amount of light hitting the subject, in order to determine the exposure. ..... several hours later you'd be ready to take a picture.

The bottom line is that for practical purposes, you either have to rely on the handheld meter or an in camera/flash metering system to determine exposure. Knowing the perfect guide number isn't going to help in any useful way, other than to tell you your range is limited with any flash.

Ardpatrick · Aug 1, 2024

Sharktooth said:
Modern flash units like the Nikon SB800 are designed to be used in a closed loop system. There is a computer in the camera that communicates with the flash, and controls its output. Modern cameras have multiple flash sensors in the camera that feed information to that computer. The computer also gets information about subject distance from the autofocus system. All of this is designed to calculate good exposure in microseconds, without the user needing to do any of these calculations manually. Using one of these flash units in manual mode makes no sense, unless you have a very specific application that needs it. In that case, a suitable hand held meter would be appropriate.

The Nikon SB800 offers a manual mode, since they've had a long history of supporting their older cameras and technology, and also for times when someone might want to use one of these flashes in a studio setting/fixed environment. If you're using manual mode, then you should be using a handheld meter anyway, so there's no need for them to invest a lot of time and money to develop a "dumb" manual system.

The A mode (automatic mode) is a throwback to the 1970's. These flash units had a single light sensor to read the reflected flash light, and a basic microprocessor to cut the flash when the appropriate exposure was achieved. The camera is not involved in any of this, except to trigger the flash. The A mode is therefore useful for older cameras that don't have any internal flash metering capability (1970's and older), The disadvantage of these flash units is that the single metering cell has all the same limitations as a single cell ambient meter in the camera. It just gives an average reading, and has no way to account for the type of subject matter.

Once you get into the mid/late 1980's and newer, matrix metering is now extended to the flash metering system. The Nikon F5, for example, has 5 cells to read flash, so it's much better at analyzing a scene than any singe cell metering system.

Bottom line, stop worrying about the flash to meter comparison, since it's meaningless for the actual usage of the flash.

For your older film cameras, use the flash mode that suits the camera. Use A mode for cameras that don't have any internal flash metering capability. When using the flash with those cameras, be aware that you've only got a single averaging meter in the flash unit, and all the drawback that implies.

Most of the autofocusing Nikons will have some type of flash controller in the camera, so use the appropriate mode for the camera.

If you're using the SB800 in a studio or other fixed setting, and off the camera, then just use your Sekonic to determine the appropriate exposure.

I’m sure the Flash photography 101 lesson is useful to some future reader, but I for one have been working with photography for about 35 years, and already know this information. My query was much more specific. My sense from other contributors posts, which are universally generous and informative, is that we are amongst a highly informed group. Thanks nonetheless for contributing.

Nikon SB 800 vs Sekonic L558

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