Nikon SB-24 and F100

[deantaylor]

<h2 > </h2>

 

 

<blockquote >hello<br /><br />a beginner asks about the compatibility of the Nikon F100 and the SB-24, specifically whether TTL is an option...differing viewpoints here--some argue that manual mode on the flash is the only option, others comments seem to contradict (possibly a misread):<br /><br /></blockquote>

 

 

<em>Specifications for Nikon SB-24 TTL AF Speedlight<br /><br />Electronic construction: Automatic silicon-controlled rectifier and series circuitry<br /><strong>Flash exposure control: TTL automatic control with Nikon F5, F100...</strong></em>

 

 

<blockquote >

 

 

<em><strong> </strong></em>

 

 

<a href="http://www.mir.com.my/rb/photography/hardwares/classics/nikonf4/flash/SB24/" target="_blank">http://www.mir.com.my/rb/photography...f4/flash/SB24/</a><br /><br />is TTL an option for the F100, or, only with CPU lenses, or other specific conditions (language misread in the otherwise comprehensive article)?<br /><br />also...<br /><br />how to interpret the GN, according to the linked article:</blockquote>

 

 

 

 

<em>Guide number (ISO 100, in): 118 (ft), 36 (m)</em>

 

 

<blockquote >do we simply multiply that 118' figure by the f stop being used?<br /><br />thank you</blockquote>

 

 

[User_1172872]

<p>I used an SB-24 in ttl mode with an F100 for many years, no problem. If you divide the guide number by the aperture used that will give you the distance at which the subject will be correctly exposed ... more or less. The stated guide number is based on an assumption of a subject of 'average' reflectance indoors in an 'average' room or something like that. Not to worry, though, I found the ttl metering of the F100 worked quite well.</p>

[jim_momary]

<p>Pages 77 - 86 of the user manual spell it all out.<br>

http://www.cameramanuals.org/nikon_pdf/nikon_f100.pdf (donation appreciated)<br>

or<br>

http://cdn-10.nikon-cdn.com/pdf/manuals/archive/F100_En.pdf (free)</p>

<p>Guide Number = Aperture X Distance</p>

<p>So, to answer you, no, you divide 118 by the F Stop. E.G., 118 / "F8" = 14.75 feet ( assuming ISO 100 film ).</p>

<p>Nice camera and flash combo. Enjoy.</p>

[deantaylor]

<p>of course...</p>

<p>and, for a more sensitive film--ISO 400--the GN increases fourfold?</p>

<p>thank you</p>

[User_1172872]

<p>If you go from ISO 100 to ISO 400 the guide number doubles. The change is equivalent to two stops. So if the correct aperture is 5.6 at ISO 100 the correct aperture changes to 11 at ISO 400. At the same distance the gn would have to double.</p>

[deantaylor]

<blockquote>

<p>At the same distance the gn would have to double.<br>

</p>

</blockquote>

<p>at the same distance, would the flash setting, then, be too powerful for that setup?</p>

[BrianS1664879711]

Since we generally focus and determine the

distance of the composed image and then set aperture on the camera, a better derivation of the formula is

GN divided by idistance equals aperture.

[BrianS1664879711]

In TTL mode, though, you don't need to do the

arithmetic

[deantaylor]

<p>for the 4x5 Speed Graphic, the formula is necessary to the setup, though...</p>

<p>...regarding the Gossen Luna Pro you had mentioned, it can be used in lieu of the 'sunny 16' evaluation<br>

card...the meter provides the aperture and speed settings for the lens-to-subject distance, and it is<br>

directed at the subject from the lens--not at the subject directed at the light source--correct?</p>

<p>Best,</p>

<p>D.</p>

<p> </p>

[BrianS1664879711]

On a f-100 you'd be using TTLmode. For the

Graphic manual mode would work, but so should A

mode. Guide number arithmetic only needed for

manual. The display will tell all for both TtL or A

[BrianS1664879711]

The LunaPro works in both reflected ( point at

scene) or incident (point at camera) modes.

[BrianS1664879711]

The Luna pro does both reflective and incident

metering.

[chuck]

I haven't used my F-100 in 10 years, so I am speaking from slightly hazy memory.

 

SB-24 was released around 1988, and was the last high end flash Nikon made before Nikon rolled out their at the time highly regarded d-TTL system in 1992, which used lense with special focal distance encoding chip (D chip) to transmits the focal distance of the lens to the camera to allow the TTL flash control to improve it's estimate of the right amount of flash output.

 

F100 was released around 1999 and supported the full d-TTL. But it will also support standard TTL when you use lenses without the D chip or flashes that were released before the introduction of d-TTL.

 

So F100 will work with SB-24 and any lens in the normal TTL mode. but F-100 won't work with SB-24 in the d-TTL mode. D-TTL is only available when you mount a distance encoded lenses (AF-D, AF-S, DX, and G lenses) on the F-100 along with any of SB-25, 26, 27, 28,

28Dx, 50DX, 600 and 800. But not the SB-24.

[rodeo_joe1]

<p>Dean, Guide Numbers are got by multiplying the F-number for a correct exposure by the distance from flash to subject. So to calculate the correct F stop to use, you need to <em>divide</em> the GN by the distance. There are two GNs given - one in Feet and another in Metres, depending on which measuring system you prefer to use. Conventionally the GNs are given at an ISO of 100. And as already posted the GN is doubled when going from 100 ISO to 400. Each doubling or halving of film or sensor speed multiplies or divides the GN by a factor of root 2 (1.414), because that's just the way that F-stop numbering works.</p>

<p>Take absolutely no notice of the fictional Guide Numbers given by flash equipment makers. The real and measured GN of my SB-24 is only 28 (metres/100 ISO) at the 50mm zoom setting. Same goes for every speedlight and portable flash I've ever owned or used; the maker's GN is about one stop optimistic compared to a good full exposure or flashmeter reading. Using a GN of 28 (m) or 92 (ft) at 100 ISO with your SB-24 will give you a proper exposure in an average room setting. (Not the white tunnel that Nikon obviously use to measure the flash output in.)</p>

[ellis_vener_photography]

"And as already posted the GN is doubled when going from 100 ISO to 400. "

 

Are you sure about that? ISO 100 to 400 is my a doubling but a quadrupling of film sensitivity. 100 to 200 would be a

doubling.

[rodeo_joe1]

<blockquote>

<p>"And as already posted the GN is doubled when going from 100 ISO to 400. "<br>

Are you sure about that?</p>

</blockquote>

<p>Absolutely Ellis. A Guide Number is got by multiplying distance by F-number, and F-numbers are based on the square root of two - 2, 2.8, 4, etc. Doubling an F-number results in a two stop difference, or a linear change in exposure of 4 times. Therefore quadrupling the ISO speed only results in doubling the GN.</p>

<p>For example: Say the GN is 28 in metres at 100 ISO and the subject is 10 metres away. That would result in an aperture of f/2.8. Now we raise the ISO to 400 and double the GN to 56. Divide the GN by 10 again and we get f/5.6, which is a two stop increase in aperture number or fourfold decrease in linear exposure.</p>