1/10 of a stop

[atina_de_greffuhle]

<p>For me it's not a problem to do the maths, square roots and logarithms and stuff. If only I had a complete guide to the mathematics of photography I could do a few things easily. Regarding this, for example:</p>

<p>http://www.photo.net/beginner-photography-questions-forum/00bmhk</p>

<p>Because here's another problem for example.</p>

<p>Take a look at this:</p>

<p>http://www.gossen-photo.de/english/foto_p_digisky.php</p>

<p>It is a Gossen Digisky light meter. It shows ƒ/11 and 1/125 shutter speed for ISO 100. But – there is a <strong>+0,2</strong> after 11. Which, I presume, means 2 tenths of a stop higher.</p>

<p>Now I have no idea how to set it up. I know cameras work in thirds of a stop, but just for example.</p>

<p>If I can't set the aperture in tenths of a stop, <strong>how can I set ISOs and shutter speeds in tenths of a stop</strong><strong>? </strong>What is one tenth of a stop higher from 1/125? It's probably something silly, but I can't figure it out right now and I just need the equation and I'm all set.</p>

[bebu_lamar]

<p>You see that the 0.2 is after the f/11 and it meant f/11 and 0.2 of a stop and not the 1/125 or ISO 100 and 2/10 of a stop. <br>

Now in the old days you simply set the aperture ring 2/10th of the distance between the f/11 marking and f/16 marking. </p>

[steve_mareno1]

<p>The only equation that I know is that it probably doesn't matter. Getting within a half stop is fine, and your pic should look exactly like one taken by a half stop more, or less.</p>

[William Michael]

<blockquote>

<p>"If I can't set the aperture in tenths of a stop, <strong>how can I set ISOs and shutter speeds in tenths of a stop</strong><strong>?" </strong></p>

</blockquote>

<p>With mostly all cameras, lenses (and filters), you can <strong><em>NOT</em></strong>. </p>

<p>WW</p>

[Lou_Meluso]

<p>Most standard DSLR's won't give <em>you</em> the ability to control exposure in 1/10th stops. However in some cameras, in Aperture priority auto mode-you set the aperture and the camera selects the shutter speed-may be able to set infinite "in between" speeds on it's own. That would depend on the resolution capabilities of the auto exposure algorithms used in the camera. I can't think of any that resolves that finely but there could be.</p>

<p>In old style large format lenses/shutters, with infinitely variable aperture adjustment, one could get close to a 1/10 although, being a mechanical device, a 1/6th was more achievable with any precision. </p>

<p>Where one <strong>can</strong> get fairly precise 1/10 stop change is when using professional studio strobe lighting equipment with digital control over the output such as those made from Broncolor. </p>

<p>I suppose using the <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html">inverse square law</a>, and a point source of light, one could calculate 1/10 stops using the distance of the light source to the subject.</p>

[Wouter Willemse]

<p>In my humble opinion, 1/10th of a stop would have so little effect on the actual exposure that there basically is no need to adjust either shutterspeed, ISO or aperture for it. That level of precision is not going to make a difference between a ruined exposure and a perfect one.<br>

Given this question is in the beginner's forum, in that spirit: I think honestly if you start wondering about details such as these, you run a high risk of getting lost in the technical details, rather than focussing (no pun intended) on the actual image. The maths behind photography are important, but keep them as simple as possible so you free up as much mind as possible for creativeness to flow freely.</p>

[bebu_lamar]

<p>Generally a modern DSLR would only let you set all those settings in 1/3 stop increments. You would simply set them to the nearest 1/3 stop for example the f/11 and 2/10 I would set it at f/13. As far as I know even with modern cameras they are not accurate to 1/10 stop any way be it aperture or shutter speed. </p>

[john_wheeler6]

<p>HI Atina de Greffuhie<br>

The disiky can be set to display in 1/1, 1/2, or 1/3 stops. The fractions in 0.1 amounts is the measured correction value to show where you stand in between the stop values.<br>

Exciting for those with the analytic persoanity and very frustrating to those that want to follow instructions to the letter yet can't figure out how to do 1/10 stops on the camera yet the accuracy is way beyond of what you can set accurately or tell in the end result image you take.<br>

There is an assumption that the measured value on the digisky can be accurately duplicated on the camera. That is very misleading. The typical DSLR is typically only within 1/2 stop of accuracy relative to an absolute light measurement. Just look on the ISO camera manufacturing settings vs the actual measured ISO values at dxomark.com<br>

So unless you know you have calibrated and matched exposure values between the digiski and your camera (or laboratory equipment), set the readout to 1/3 stop and just use those values and ignore the measured correction value. <br>

There is an expression I have heard and used called "Getting wrapped around the axle". It basically means when one gets confused to the point of paralysis. Such topics such as 1/10th of a stop will do exactly that. I hope the thoughts above (and others that have posted) will get you unwrapped from around the axle. :)<br>

All IMHO of course.</p>

[SCL]

<p>Atina - not to dash water on your desire for "exact" measurements, let me momentarily look at another side of exposure - shutter speed. Unless you are using a recently accurately adjusted electronic shutter, you will generally have a manufacturer's tolerance of between plus or minus 1/2-1/3 stop in shutter speed variance, which isn't consistent from shot to shot. That is why when I acquire a new (old) camera, I usually run a series of tests with a shutter tester to see what the variances are at each designated speed. !/10 of a stop exposure difference, except in scientific work where a high degree of accuracy may be required, is just plain ridiculous, and virtually unachievable - at least in the film world, because ISO designations themselves are so loose, as are the development variables. Like others have said, get beyond the finite details and take some pictures.</p>

[paddler4]

Atina,

 

+1 Wouter. The short answer is: forget about it. The 1/3 stop intervals on most modern cameras are sufficient. In fact,

many manual film cameras, including the ones I grew up with, had intervals of 1/2 stop. The difference between the o.2

you want and the 0.33 most cameras will give you is inconsequential.

 

Dan

[Alan Marcus]

<p>The f/stop number set is based on a delta of 2x meaning the next value in the number set increases the exposure by doubling the amount of light energy playing on film or digital chip. The value 2 can be expressed as 10^0.30. In other words, 10 elevated to the 0.30 power. </p>

<p>The use of logarithmic values in photography dates from the works of Hurter and Driffield, the first to apply scientific principles to the measurement of the sensitivity and blackening of film due to exposure and developing. They published in 1890. Their methods remain relevant and form the bases of the sciences of sensitometry and densitometry. They used log notation because vision and hearing somewhat follow a logarithmic graph. Additionally, engineers worked in log notation, as this is the language of the slide rule allowing addition and division to be substituted for multiplication and division (important in the days before calculators).<br>

<br>

As to adjusting exposure in finer and finer increments: The capability to adjust exposure and obtain repeatable accuracy in the developed film is limited. We are talking about making an exposure change and measuring and quantifying the outcome. In a laboratory under controlled conditions, one can achieve, with due diligence, an accuracy of 1/3 of an f/stop. To consistently make repeatable changes the practical limit is 1/6 f/stop increments; easier said than done. To make 1/10 f/stop change borders on the ridiculous. Film speed (ISO) is not that steady. Adjustment to the aperture diameter involves gear backlash, shutters are not that accurate; film processing cannot be controlled closer than 1/6 f/stop. </p>

<p>Anyway, below is a table of f/stop ∆ (delta):<br>

1 f/stop =2x change (delta) = 0.30 log (base 10)<br>

2/3 f/stop = 1.585x change (delta) = 0.20 log (base 10)<br>

1/2 f/stop = 1.413x change (delta) = 0.15 log (base 10)<br>

1/3 f/stop = 1.259x change (delta) = 0.10 log (base 10)<br>

1/6 f/stop = 1.122x change (delta) = 0.05 log (base 10)<br>

1/10 f/stop =1.072x change (delta) = 0.03 log (base 10)<br>

1/12 f/stop = 1.059x change (delta) = 0.025 log (base 10)</p>

[Palouse]

<p>Some/most/all (?) modern DSLRs use < 1/3 stops when used in P (Program) mode--right? Not that that answers or even remotely addresses the question! Just a random thought!</p>

[User_6502147]

<p>Although the real DSLR world allows you to tweak the camera to a degree (close enough)....if you shoot RAW, you can adjust in edit whatever fraction of the exposure that you may desire....even 1/10th.</p>

<p>Les</p>

[jcuknz]

<p>In jpg you can still adjust perfectly well within far wider range than being discussed on this thread.<br>

I see the pre-occupastion with exposure to this degree of preciseness obstructing the purpose of getting good photographs.</p>

[david_henderson]

<p>When I used medium format film cameras with exposure critical colour slide film - up to about five years ago- I could and did quite happily set my camera to an aperture intermediate to the click stops on the lens. I did that not just because I could, but because with the film medium I used, a quarter stop could not only make a visible difference to the exposure, but also could make the differnce between detail in highlights or shadows or not. Much of the time it didn't matter that much - but sometimes it did. Some people still photograph like that.<br>

With digital the sensors are less critical than slide film. A quarter stop out is rarely going to be worth adjusting for, never mind important- and most times you could handle that in post if you wanted.</p>

[nico_morris]

<p>The lightmeter is giving readings like that to show how precise it is. It doesn't mean you can follow its exposure estimation so precisely. I wouldn't bother dialing in a fifth of a stop difference though sometimes in post processing I work to one sixth. I wouldn't care to work with an old camera that only does full stops though.</p>

[david_elden]

<p>Everyone: there is a good reason for the 1/10 stop resolution on electronic display lightmeters.<br>

It is not there for a typical available light exposure measurement; yes, rounding off to the nearest whole stop will usually be close enough given the latitude in modern digital cameras and negative film.<br>

It is there to enable you to measure lighting ratios easily. E.g. You measure main at 11+3/10 and fill at 5.6+7/10 and then calculate (or look up from a table) the stop difference i.e. the lighting ratio. If you round those two measurements off to whole stops you are going to have the risk of a large error in the ratio estimate so there you do have a real need for the 1/10 readings.<br>

Dave.<br>

</p>

 

[western_isles]

<p>I would forget about the 1/10th of a stop as it is meaningless for most photographers. </p>

<p>I have only ever bracketed exposures in 1/3 or 1/2 stops and this allows you to see the actual differences between images.</p>

<p>Forget the maths and enjoy your photography:)</p>