How much ISO to make up for one stop loss?

[mark_thomas17]

<p>Let's say, I need 2.8 but my lens only goes to 4. I'm at 100 ISO. Roughly how high should I increase my ISO to emulate f2.8.</p>

[leslie_cheung]

<p>Is this a joke or trick question?</p>

[craigd]

<p>If you need one stop, change ISO by one stop, that is, from 100 to 200.</p>

<p>The concept of "stops" is applicable to exposure time, aperture, and ISO. A change of one stop in any of them can be balanced by a change of one stop in the opposite direction in either of the others. So if an external meter tells you to shoot at f/2.8 and you can only do f/4, either increase ISO or exposure time by one stop.</p>

<p>Also, this "emulation" (as you put it) is only relevant to getting a proper exposure. You can't really "emulate" f/2.8 in any other sense -- if you're shooting at f/4, you get the depth of field of f/4.</p>

[Dieter Schaefer]

<p>double - so its ISO 200. No roughly about it either.<br>

Here is the f-stop scale</p>

<p >f/1<br /> f/1.4<br /> f/2<br /> f/2.8<br /> f/4<br /> f/5.6<br /> f/8<br /> f/11<br /> f/16<br /> f/22<br /> f/32<br /> <br /><br>

Each f-stop on the scale lets in half as much light as the previous one . So f/1.4 lets in half as much light as f/1, f/2 lets in half as much light as f/1.4 and so on.<br>

ISO sets your camera’s sensitivity to light. ISO 200 is twice as sensitive to light as ISO 100; ISO 400 is twice as sensitive to light as ISO 200 and so on.</p>

[hjoseph7]

<p>ISO only affects the light gathering ability of your sensor. While aperture not only affects the light gathering ability, it also affects the Depth Of Field. Some cameras let you change the ISO in 1/3 increments, but a full Stop would mean going from lets's say ISO 100 to ISO 200, or ISO 200 to ISO 400. So lets say you are at ISO 200 and F4, to obtain the same light gathering capability that you do at ISO 200 and f2.8, you would have to change your ISO to 100.</p>

[craigd]

<blockquote>

<p>ISO only affects the light gathering ability of your sensor.</p>

</blockquote>

<p>It may seem that way to the photographer, but really the sensor gathers just as much light at any ISO setting. What ISO changes is the amplification of the signal. The reason higher ISOs look noisy is that amplification increases not only the signal but also the noise.</p>

<blockquote>

<p>So lets say you are at ISO 200 and F4, to obtain the same light gathering capability that you do at ISO 200 and f2.8, you would have to change your ISO to 100.</p>

</blockquote>

<p>Uh... no. f/2.8 is one stop more exposure than f/4, but ISO 100 is one stop less than ISO 200. If you need one more stop of exposure than ISO 200 f/4, you can either go to f/2.8, or ISO 400, or you can reduce shutter speed by one stop.</p>

<p>The OP's example was being at ISO 100, f/4 and wanting the exposure equivalent to ISO 100, f/2.8. He should either change ISO to 200 or reduce shutter speed by one stop (e.g. if he's at 1/250, he could change to 1/125).</p>

[mark_thomas17]

<p>Very helpful, thanks for the responses.</p>

[john_macpherson]

<p>Everything in photography:<br>

apertures going up and down (f8/f11/f16),<br>

shutter speeds going higher and lower (1/250, 1/125, 1/60)<br>

and ISO settings up and down (100, 200, 400)</p>

<p>is a halving and doubling series.</p>

<p>You go one way you double the exposure, you go the other way you halve the exposure. (assuming no 1/3 stop settings of course). Easy.</p>

[steve m smith]

 

<blockquote>

<p>Is this a joke or trick question?</p>

</blockquote>

<p> <br /><br />It's not a joke to someone who doesn't know the answer and it's certainly not a trick question.</p>

<p> </p>

[mukul_dube]

<p>I was as puzzled as Leslie. How can someone not know something so basic and yet speak of ISO settings and f/4, clearly knowing that the latter differs from f/2.8?</p>

[Rick Helmke]

<p>The question made perfect sense to me. Part of the learning process we all go through.<br>

<br />Rick H.</p>

[jcuknz]

<p>Everybody has to learn at some stage even things which others consider basic.<br>

Glad the point of amplification was clarified.</p>

[mukul_dube]

<p>Looks like learning and teaching have changed in half a century. Geometric progression was perhaps the first thing I was taught about lenses and cameras. This although shutter speeds went 1/1, 1/2, 1/5, 1/10, 1/25 ..., on Leicas and on Rolleicords. Film speeds were another matter, as ISO (ASA/BS arith.) was not the only scale in use -- DIN (log.) was also used fairly widely (Scheiner and GOST were relatively uncommon but were still encountered occasionally, and of course there were the Weston speeds). Camera manuals once came with a simple explanation of exposure.</p>

[jay_poel]

<p>f stops - 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 64 | The smaller the number, the larger the aperture. </p>

<p>shutter speed - 1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1s ... | The smaller the number, the shorter amount of time the shutter is open.</p>

<p>ISO 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800, 25600 .... | The lower the number, the less sensitive the sensor is to light.</p>

<p>f stops have to be memorized but shutter speed and ISO you can multiple or divide by 2 for a full stop.</p>

<p>I hope this helps. I know I found it easier to understand when I saw something similar.</p>

[bob_sunley]

<p>Multiply stop values by 1.4, and you missed f45 between 32 and 64. :)</p>