What is one third step?

<p>Please any one can define one third step in photography</p>

<p>It's possible that you mean one third of a <em>stop</em>. <br /><br />When you change the amount of light contributing to your exposure (by altering the shutter speed, or the lens aperture), doubling that light mean increasing by one stop. <br /><br />So, changing your lens opening from f/5.6 to f/4 is considering opening up one full stop because you're letting in twice as much light. Likewise with changing the shutter speed from, say, 1/250 to 1/125.<br /><br />But sometimes those full-stop changes are too much. If you only change the value by a third of a stop, you're making a more incremental change. Modern DSLRs will often allow for settings in thirds of stops, to allow for more subtle changes. So, changing your lens from f/4 to f/4.5 is a one-third-stop change.<br /><br />You can see charts <strong><a href="http://en.wikipedia.org/wiki/F-number">here</a></strong>.</p>

<p>One third of a step would be an increment in a system where the doubling of exposure occurs every three increments. For example: in a sequence of shutter speeds like, . . . <strong>6</strong><strong>0,</strong> 50, 40, <strong>30</strong><strong> </strong>. . . , the amount of light at 1/60 would be doubled at 1/30. Yet, going from 1/60 to 1/50 would be a (one third) step. Usually this is referred to as a "step" in English. We leave out the one third idea.</p>

<ul>

<li>60 to 50 would be a step (of one-third value to the next stop)</li>

<li>50 to 40 would be a step (of another third's value to the next stop)</li>

<li>40 to 30 would be a step (of the third third's value to the next stop)</li>

</ul>

<p>From 1/60 to 1/30, in one leap, would be a stop.</p>

<p>I have never seen anyone fuss over one third of a step, inside the step itself. I imagine that would be an unnoticeable change. More likely lost in translation.</p>

<p>In many systems, the shutter speeds are set to double in a sequence that is similar to f/stops. This is the most common setup on the shutter speed dial. <br /> For example, f/stops would double the amount of light let in as: f/16, f/11, f/8, f/5.6, f/4 and so on. Each increment would let in twice as much as the one before.</p>

<p>If the system of measurement is based on a factor 1/2 (or 2), then it is referred to as a "stop."<br /> If the system of measurement is based on a factor 1/3 (or 3), then it is referred to as a "step."</p>

<p>Steps are usually only used for shutter speed and film speeds.</p>

<p>If the photographer has his shutters operable in steps, and his lenses in stops, he'll have the most increments of control available through the shutter and aperture controls. Some digital cameras can be set up to do this; my Pentax does it; it's probably common.</p>

<p>If the photographer sets up his shutters (DSLR) in stops and his lenses in stops, he'll have fewer increments to deal with, but a simpler logic problem to solve with exposure. [The next click of either shutter or aperture dial will halve or double the previous amount of light let in. With a shutter dial set to steps, the photographer would have to remember and count his clicks over, instead of just making one.]</p>

<p>Either method is acceptable. Just remember which one you are using on the shutter or film speed/sensitivity dial at the time.</p>

<p>Can someone please reccomend a basic photography book in Vinod's native language, so he can learn more easily these basic things?</p>

<p><Chas></p>

<p>If you are on a stop, then there are <strong>three steps to the next stop</strong>.</p>

<p>If you look at the dial, and there aren't three clicks between the stops, then what you have are stops and half-stops.</p>

<p>Three steps to the next stop is the old way. Stop to stop is the easy way.</p>

<p>If you only have a basic light meter, you can get the steps by making a quick adjustment to the film speed dial. Remember to set it back. </p>

<p>Some of the really basic light meters will have the steps printed as dots between the common film speeds. Like on a dial, it will show: 25 * * 50 * * 100 * * 200 * * and so on. Those marks with the * are the steps. </p>

<p>On those same types of light meters, it will be common to have the shutter speeds and f/stops in stops. So, you may have to think a little to figure up the step-based measurement when operating that basic equipment. The new equipment will be fancy. The digital cameras will be settable for steps and stops. The digital spot meters will read in tenths! That is, the stop and then how many tenths above that stop. Like a reading of f/8.3 would be f/8 plus a step. </p>

<p>Ansel Adams used steps and stops in his book <em>The Negative</em>. It is a good photo book that explains and uses steps.</p>

<p>Please write back. Hope this helps. J.</p>

<p>The step comes from English speaking systems about film speed. If you use Russian or German film speed systems I think they just gave a separate number for each step. 21, 22, 23, 24, and so on. </p>

<p>There is a slight error above. If you want to go from 1/30 to 1/60 in 3 steps, the points in between are not actually 1/40 and 1/50, but they are pretty close. It's more like 1/30, 1/37.8, 1/46.2, and 1/60.</p>

<p>Mathematically, multiply or divide by the cube-root of 2 to move by steps, and multiply or divide by the square-root of 2 to move by stops.</p>

<p>Neal, I'm not sure we're all on the same page when it comes to the difference between steps and stops but both of the following can't be right:</p>

<blockquote>

<p>Mathematically, multiply or divide by the cube-root of 2 to move by steps, and multiply or divide by the square-root of 2 to move by stops</p>

</blockquote>

<p>If you're talking about apertures (f numbers), then it's the sixth-root of 2 for 1/3-stops (steps, apparently, although I've never heard that definition before) and square-root of 2 for stops.</p>

<p>If you're talking about shutter times, then it's a factor of a cube-root of 2 for a 1/3 stop difference, and a factor of 2 for a full stop difference.</p>

<p>I think this may be bringing confusion to the original question though. Put simply, a stop is a 1EV change in how much light the recording medium will be allowed to see. You can 'open up' (increase light) or 'close down' (decrease light) a stop using shutter, sensitivity (ISO, change film or adjust sensor), or aperture. Each 1EV change to any of these parameters doubles or halves the amount of light.</p>

<p>Steps are fractions of 1EV stops. Depending on the equipment, these steps may be in 1/3 or 1/2EV increments. Sometimes a camera will have both, so you can theoretically combine them for 1/6EV precision but how meaningful that is is debatable; most of the time 1/3 steps is plenty of precision.</p>

<p>Historically (on mechanical cameras), shutter speeds were normally in 1-stop increments, sensitivity (film speeds, for calibrating the light meter) in 1/3 step increments, and aperture might be in 1, 1/2, or 1/3 EV increments. Some cameras would also offer exposure compensation, a way to temporarily bias the lightmeter without changing the base film speed setting. These also came in 1, 1/2, or 1/3 EV increments. For Pentax, many of the older cameras (like an ME or Super Program) that had exposure comp had their dials marked as 1/4x, 1/2x, 1x, 2x, 4x--these are 1EV increments, indicating -2EV, -1EV, 0, +1EV, and +2EV, respectively. The professional-level LX, and the 645 medium format camera of the early 80's had shutter speed in manual 1EV increments but had exposure comp in 1/3EV steps--this degree of fine control was popular for people shooting slides.</p>

<p>John, I also shoot Pentax and am somewhat confused about a few of your points. What you say has the ring of truth if you're using an old manual focus lens that has an aperture ring--the aperture ring steps are normally either 1/2 EV steps or 1 EV stops. For Pentax lenses, this is usually 1/2 EV through most of the range, sometimes with 1 EV stop at the extremes--for example, Pentax doesn't usually include the 1/2 step between f/16 and f.22. On the more modern cameras & lenses, where the body is controlling the aperture, you can choose 1/2 or 1/3 EV steps, but it applies to both shutter speed and aperture--you can't configure shutter speed to one and aperture to the other.</p>

<p>So it is not unusual at all to control aperture in 1/3 EV steps. Even with manual focus, there have been lenses (Leica, perhaps?) that offer 1/3EV steps on their manual aperture rings.</p>

<p> </p>

<p>Dear All<br>

Thanks for ur comments,but i have asked above question for DSRL camera,i want to know one third step knowing exposer.For example</p>

<p >F 5.6/160 = + 1 stop</p>

<p >F 5.6/80 = +1</p>

<p >F 5.6 /40 = +1</p>

<p >F 5.6 /20 = 1/3 STEP</p>

<p > </p>

<p >THIS IS THE SIMPLE EXAMPLE BUT I WANT TO KNOW DEFINATION IS SIMPLE WORD.</p>

<p >REGARDS<br>

 

 

</p>

<p>Vinod, "F5.6/160=+1" stop isn't right. F5.6 / 160 is an exposure setting. It cannot be +1 unless it is compared to another exposure. Same applies to your other exposure settings (F5.6/80, F5.6/40, and F5.6/20). However if we consider F5.6/160 as the correct exposure (as recommended by your cameras light meter) then your example changes to:<br />F 5.6/160 = correct exposure<br />F 5.6/80 = +1 stops from correct exposure.<br />F 5.6 /40 = +2 stops from correct exposure.<br />F 5.6 /20 = +3 stops from correct exposure.<br>

<br />Another example that might be helpful to you is:<br />F5.6/160 = correct exposure<br />F5.6/<strong>80</strong> = +1 stop from correct exposure.<br />F5.6/<strong>40</strong> = +2 stops from correct exposure.<br /><strong>F8.0</strong>/40= +1 Stop from correct exposure.<br /><strong>F11</strong>/40 = correct exposure.<br />F11/<strong>30</strong> = +1 step from correct exposure.<br />F11/<strong>50</strong> = -1 step from correct exposure.<br /><strong>F10</strong>/50 = correct exposure.<br />Note I highlighted the change from the previous exposure in <strong>Bold </strong>to help make the example more clear. I hope this helps.</p>

<p>Thanks you very much Steve for your example.but can u xxplain me detail who we take correct one third step?<br>

Regards<br>

Vinod</p>

I suppose if the correct exposure is f8/160 and you are at f11/160 then you are one step away from the correct exposure. And that one step is to open up one stop either to f8 or 80. This sounds more like a matter of semantics to me.

<p >Exposure is a measure of how much light energy has beens delivered to the film or digital chip during the time the shutter is open. </p>

<p >The job of the lens is to project an image of the outside world onto the light sensitive surface of this material. We can adjust the strength of the exposing light by opening up or closing down the aperture of the lens. This is a control over the working diameter of the lens and is known as an aperture adjustment. </p>

<p >We can adjust the strength of the exposing light by changing the shutter speed. This control increases or decreases the duration (time) of the exposure. </p>

<p >The measure of the exposure comprises both aperture adjustment and shutter speed adjustment. </p>

<p >If too much light energy is delivered during the exposure, we say we have over exposed. The result is a picture that will be too light. If too little light energy is delivered, we say we have under-exposed. The result is a picture that will be too dark.</p>

<p >All digital chips and film allow some room for error. In other words an exposure error, if not too severe, this may not result in an unsatisfactory picture. We call the permissible error exposure latitude.</p>

<p >By tradition, the adjustments increment we use to cause a change to the exposing energy is a doubling or halving. This increment is a 100% increase or a 50% decrease when we reduce. </p>

<p >When we adjust the lens we are changing the working diameter. The is accomplished by an adjustable aperture. The aperture is a washer shaped obstruction that restricts the working lens diameter. Because the aperture restricts the passage of light, it is called a stop.</p>

<p >While it is tradition to make these adjustments by doubling or halving the exposing energy, sometimes this will be too coarse. If true we make changes in 2/3 increments. Sometimes even this is too coarse so we make a finer adjustment using 1/3 increment. Except for the most critical of work making adjustments using a fractional stop are ineffective. </p>

<p >A doubling of halving is called a full stop. Smaller changes are fractional stops such as 2/3 stop or 1/3 stop.</p>

<p >Sorry there is no single word that defines changes made in increments of 1/3 stop. </p>

<blockquote>

<p>Thanks you very much Steve for your example. But can you explain me in detail who we take correct one third step?</p>

</blockquote>

<p>The camera meter is a simple device. It just measure light comming in. However for various reasons it might not always get it right. Experienced photographers will recognize these situations and adjust the the exposure away from the meter reading to get the image to look the way you want. <br>

For example your taking a picture if a plant with a very small red flower. The camera meter won't see the flower because it is too small (the light meter is a different part of the camera, it is not the image sensor). You take a pictue of tha plant and look and then you notice on the histogram that there the red pixals of the flower are overexposed in the image. So to correct for that overexposure you would have to change the shutter/aperture/iso setting. One or two steps might be needed or you might find an image that would take severs stops (or more) of adjustment.</p>

<p>In other cases the photographer might deliberately under or overexpose an image because he want is darker or brighter than normal to get the look he wants. In other cases a portion of the image might be moving a little due to the wind while most of the background might be stationary. The photographer might not want to adjust the aperature/iso becased he needs some depth of field from the lens and doesn't want the image noise associated with higher iso. But when the meter sets the shutter speed the resulting image has motion blur that doesn't look good. The solution might be as simple as speeding up the shutter by -1 or -2 stops and then adjusting the image in a computer later to correct for the overexposure. </p>

<p>When a photographer says he adjusted the exposure by -2 steps he is simply saying the he was fine tunning the exposure to get exactly what he wanted.</p>

<p>Thanks Alec for catching my mistake. I should have clarified I was referring to shutter speeds. What I meant to say was:</p>

<p>Mathematically, multiply or divide by the cube-root of 2 to move by steps (1/3 stops), and multiply or divide by the square-root of 2 to move by 1/2 stops.</p>

<p> </p>

<p >A tip of the hat to Neal!</p>

<p >The basis of the f/stop number set:</p>

<p >Construct a circle on paper with compass. Measure its diameter and calculate its area.</p>

<p >To calculate a revised circle with twice (200%) the surface area, multiply diameter by square root of 2 1.414).</p>

<p >The number set in full stops is:</p>

<p >1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 16 - 22 - 32 -45 -64 (full stops) note each number going right is it neighbor on ht left multiplied by 1.4. Each number going left is its neighbor on the right divided by 1.4.</p>

<p >To calculate a revised circle with 150% the surface area, multiply diameter fourth root of two 1.18920. </p>

<p >The number set in 1/2 stop increments:</p>

<p >1 - 1.2 - 1.4 - 1.7 - 2 - 2.4 -2.8 - 3.4 -4 - 4.8 - 5.7 - 6.7 - 8 - 9.5 - 11 etc.</p>

<p >To calculate a revised circle with 133% the surface area, 133% larger, multiply diameter by sixth root of two 1.1225</p>

<p >The number set in 1/3 stop increments:</p>

<p >1 - 1.12 - 1.26 - 1.4 - 1.6 - 1.8 - 2 - 2.3 - 2.5 - 2.8 - 3.2 - 3.5 - 4 - 4.5 - 5 - 5.6 - 7 - 8 etc.</p>

<p>Can anyone show how to solve something like the following example, in a simplest way you know:<br>

The Nikon P60 has only two apertures F3.6 and F8.5 when the lens is at the widest end (we know that these numbers 3.6 and 8.5 are only approximate but lets assume they are exact numbers and try to be as accurate as possible). we want to have the same exposure as the setting (F3.6, 1/500s) but with the lens closed down to F8.5. What would be the shutter speed?<br>

Exposure (F3.6, 1/500s) = (F8.5, ???)<br>

Also, how many Fstop is it from F3.6 to F8.5?</p>

<p >Since the apertures of lenses are circular, we can use the geometry of circles to solve:</p>

<p > </p>

<p >The f/number set:</p>

<p >1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 -32 -64</p>

<p >First a known example:</p>

<p >How many f/stops difference f/2 to f/16-- we can count on the number set, it's 6.</p>

<p >Let us do this by math.</p>

<p >First, pretend these values 2 and 16 are circles drawn on paper.</p>

<p >We find the area using pi times radius square.</p>

<p >The area of 2 = 3.14</p>

<p >The area of 16 = 201</p>

<p >Difference 201 ÷ 3.14 = 64</p>

<p >The larger circle has 64 times more area than the smaller. </p>

<p >Now f/numbers are elevated incrementally in powers of 2.</p>

<p >To find the number of f/stops that separate - Now to find out how many times we must elevate 2 to get 64?</p>

<p >The math 2 x 2 x 2 x 2 x2 x2 =64 so 6 times</p>

<p >The answerer is 6 f/stops separate f/16 from f/2</p>

<p > </p>

<p >Solving separation in f/stops between 3.6 and 8.5 using same math method.</p>

<p >Area of 3.6 circle = 10.179 square inches or millimeters </p>

<p >Area of 8.5 = 56.575 square inches or millimeters</p>

<p > </p>

<p > Now the difference by division 56.575 ÷ 10.179 = 5.575.</p>

<p >OK now we know the larger circle is 5.575 times the smaller. Now f/numbers being incremented by doubling or halving thus we need to know what number elevates 2 to equal 5.575</p>

<p >Answer 2 elevated to the 2.4789 (lets round) = 2.5.</p>

<p >Thus, we know 2 1/2 f/stops separate the two.</p>

<p > </p>

<p >The initial exposure was f/3.6 @ 1/500. We stop down to 8.5.</p>

<p >We must solve to find the revised shutter speed?</p>

<p >One f/stop's worth is 1/250 </p>

<p >Two f/stop's worth is 1/125</p>

<p >Three f/stop's worth is 1/60.</p>

<p >Two and a half f/stop's is about 1/80</p>

<p > </p>

<p >Foot note: I hate camera engineers that fail to understand they cloud the waters when they use f/stops that are not in increments of 1 or 1/2 or 1/3. Let me add, it is impossible, given the current level of precision used in shutters and aperture to make mechanical gear trains that can get better that 1/3 f/stop accuracy. </p>

<p>I found this page that would help a lot to understand the calculation<br>

<a href="http://en.wikipedia.org/wiki/F-number">http://en.wikipedia.org/wiki/F-number</a></p>