ISO

[impr_pht]

<p>Hi<br>

If i want more brightness in my image should i rather decrease the iso or increase the exposure in raw?<br>

Thank you</p>

 

[SCL]

<p>The traditional method would be to increase the exposure either by lengthening the time of the exposure or opening up the aperture. In the digital world, if one is shooting in manual mode, increasing the ISO would work as well, as it increases the sensor's sensitivity to light. The bottom line is to increase the amount/intensity of light reaching the sensor.</p>

[Wouter Willemse]

<blockquote>

<p>should i rather decrease the iso or increase the exposure</p>

</blockquote>

<p>One does not exclude the other; ISO is part of setting the exposure. ISO (the sensitivity of the recording medium) is one of three components in setting the exposure. The other two, as you probably know, are the shutterspeed and aperture. If you want to keep the same exposure, but raise the ISO (for example from 400 to 800 - 1 stop), you will need to shorten the shutterspeed by a stop, OR close the aperture by one stop. These three go always hand in hand.<br>

If you want more brightness, you'd want to overexpose - meaning you for example increase the ISO, and leave shutterspeed and aperture as they are. Overexposing in digital is tricky, as the highlights at some point will become pure white, and there is no way to recover those (also not in raw, even if that gives a bit more play). So, it is something to be done with care, and in case of doubt, you're often better off trying to alter the brightness of the raw file afterwards in your software of choice.</p>

[Alan Marcus]

<p>Images are dark if under-exposed and too light if over-exposed. One key to the photo kingdom is understanding exposure. <br>

</p>

<ol>

<li>

<p>The aperture setting (f/number): The larger the working diameter of the lens, the brighter the image it presents to the image sensor. Listed are the f/numbers starting with the brightest. f/1 – f/1.4 – f/2 – f/2.8 – f/4 – f/5.6 – f/8 – f/11 – f/16 – f/22. Your camera will likely only have values from the middle of this list. Each, going right delivers ½ the image brightness of its neighbor on the left. f/1 is a giant opening while f/22 is super tiny.</p>

</li>

<li>

<p>The shutter speed determines how long the image presented by the lens will be allowed to play on the image sensor. The shutter speed list in seconds and fractions of a second: 1/1000 – 1/500 – 1/250 – 1/125 – 1/60 – 1/30 – 1/15 – 1/8 – 1/4- 1/2 – 1 – 2 – 4 etc. Most pictures are taken using a setting that is in the middle of the fraction of a second (revolving around 1/125 of a second. Long exposure times (going right) allow more time for the image to record thus the results are a brighter image. </p>

</li>

<li>

<p>ISO – The sensitivity to light of the image sensor is adjustable. The higher the ISO setting the more sensitive the image sensor. A setting of 200 or 100 delivers highest quality. Settings of 1000 or more will likely yield substandard results. This is because, as you up the ISO, you are upping the setting of an amplifier. High amplifier setting induce a type of static we call noise. Nose is seen as a granularity akin to grain size seen when using fast photographic films.</p>

</li>

</ol>

<p> <br>

The bottom line is: Everything in moderation – we up the ISO when the light is feeble. This comes at a price. It is likely that noise is induced and the final image shows granularity. By the way, ISO is the initials of the Internarial Standards Organization. They write the rule book on how we measure the sensitivity of film. The digital camera community has adopted the ISO method of sensitivity labeling. </p>

[Palouse]

<p>This article: http://www.imagen-estilo.com/Articles/Flash/flash-photography-basics.html</p>

<p>may help, particularly the figure of the exposure triangle.</p>

[William Michael]

<blockquote>

<p>If<strong> i want more brightness</strong> in my image should i rather <strong>decrease</strong> the iso</p>

</blockquote>

<p>Just for clarity and to reiterate this point that Stephen made:<br>

When we talk about ISO in digital we usually think of "deceasing" the ISO to mean making the ISO <em><strong>LESS</strong></em> sensitive to light which means using a SMALLLER number.</p>

<p>So if you want <strong>more brightness</strong> in your image you could achieve that by <strong>INCREASING the ISO</strong> (a bigger number).</p>

<p>WW</p>

 

[paddler4]

<blockquote>

<p>The traditional method would be to increase the exposure either by lengthening the time of the exposure or opening up the aperture. In the digital world, if one is shooting in manual mode, increasing the ISO would work as well, as it increases the sensor's sensitivity to light.</p>

 

</blockquote>

<p>But changing ISO does not change the sensitivity of the sensor to light, which is important for the OP's question. It amplifies the signal coming out of the sensor to compensate for less light. So, increasing exposure (wider aperture, longer shutter speed) is not equivalent to increasing ISO. Increasing exposure increases the light hitting the sensor, but increasing ISO doesn't. This matters for two reasons. First, increasing ISO amplifies noise as well as signal. Second, increasing ISO decreases effective dynamic range.</p>

<p>So, I think the best answer to the OP is: don't increase ISO unless you need to. If you can increase the light hitting the sensor instead, that is usually better. However, if you can't--for example, if that would require too slow a shutter speed--then increase ISO.</p>

[andrewg_ny]

<p>Are you asking whether it is better (given a fixed shutter speed and aperture) to brighten the image by increasing sensitivity (greater ISO value) in camera at image capture time vs. underexposing in-camera and boosting exposure when processing the RAW file?</p>

<p>You can underexpose in-camera and brighten later but you're fighting the way the camera's designers intended it to work -- for one thing, images reviewed in-camera on the LCD may be too dark.</p>

[raczoliver]

<p>I think the OP's question is whether it is better to use a higher ISO when taking the picture or increase the brightness on a raw image in post processing.</p>

<p>Generally it is better to get the exposure right in camera. It is true that raising the ISO will result in a lower image quality, but so will brightening up an underexposed picture in post. Usually the former is more desireable.</p>

[James G. Dainis]

Changing the ISO does not increase brightness. It just changes the camera settings for the same exposure.

 

ISO 100 = f/8, 1/125 sec

 

ISO 200 = f/8, 1/250 sec

 

ISO 400 = f/8, 1/500 sec

 

or

 

ISO 100 = f/8, 1/125 sec

 

ISO 200 = f/5.6, 1/125 sec

 

ISO 400 = f/4, 1/125 sec

 

Six photos taken at the above settings will be equally bright. Make the film or sensor twice as sensitive and you only need 1/2 as much shutter speed or aperture for the same exposure and equally bright photo..

[William Michael]

<p>I interpreted that the OP was suggesting changing the ISO and not making an equivalent change in either the shutter speed or aperture.</p>

<p>For example take a shot using F/8 @ 1/125s @ ISO100 and then change to F/8 @ 1/125s @ ISO200 and take a second shot of the same scene, the second shot would be "brighter". And the OP was asking is changing the ISO as I just described better than not changing the ISO and increasing the 'exposure' (<strong>slider</strong>) in Post Production. </p>

<p>I think the OP got mixed up with the word "decrease" and meant "increase".</p>

<p>It would be good if the OP clarified the question.</p>

<p>WW</p>

[eugen_mezei]

<blockquote>

<p>But changing ISO does not change the sensitivity of the sensor to light, which is important for the OP's question. It amplifies the signal coming out of the sensor to compensate for less light. So, increasing exposure (wider aperture, longer shutter speed) is not equivalent to increasing ISO. Increasing exposure increases the light hitting the sensor, but increasing ISO doesn't. This matters for two reasons. First, increasing ISO amplifies noise as well as signal. Second, increasing ISO decreases effective dynamic range.</p>

</blockquote>

<p> <br>

Dan M, you refere to the native ISO of the sensor. I'm not an expert on this, but I guess some amplification tooks place even at that setting, just with the best possible signal/noise amplification ratio.<br>

Would it be better to shot at the native ISO and underexpose, correcting in PP or shot at a higher ISO and have not to brighten the image in PP?</p>

[frode]

<blockquote>

<p>Would it be better to shot at the native ISO and underexpose, correcting in PP or shot at a higher ISO and have not to brighten the image in PP?</p>

</blockquote>

<p>This is camera (sensor) dependent. With my Pentax K3 I very often use 1-3 stops lower ISO than the camera recommends and correct in post processing as necessary (most often on ISO 100). If I take two images of the same scene, one with correct ISO, say 1600 and one with 4 stops lower, here 100 (exposure kept the same, that is unchanged aperture and time), I can hardly see any increase in noise at all. I can however easily see decrease in dynamic range (4 EV in this case) for high contrast images. Look at the lamps on the attached image. Especially when photographing back lit scenes, maybe including the sun or sunlit clouds on the sky I keep the ISO well below what the camera says, some times even 5 stops (5 stops is the limit of adjusting exposure in Adobe Camera Raw).<br>

There are of course situations where you should avoid this strategy. Raising the exposure in very dark areas might give you some problems, especially with banding/pixelisation type noise. Other camera sensors will have more of so called "read noise" which in (very) short is noise that will increase signal to noise ratio with higher ISO, especially for the lowest ISO values. Typically these cameras will show no or low increase in dynamic range towards the lowest ISOs. For these cameras you should almost never use the above strategy as I use for the K3. Experience will show you how much your camera will take before things start to happen.</p><div></div>

[frode]

<p>And here is how the images looked with ACR default settings (and how they would look at the camera's LCD screen). Somebody will call the ISO100 image underexposed. I suggest that the ISO 1600 is overexposed, even though it looks correct on the camera LCD screen and even if most light meeters will tend to suggest an exposure in the same ballpark.<br /> BTW: This strategy is nothing that I have developed myself. It is often refereed to as "expose for the highlights" and keeping ISO low gives more headroom (dynamic range) for doing exactly that.</p><div></div>