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What is camera ISO? Help with digital ISO with this simple guide – Digital and film ISO explained
Posted on October 6, 2007 | 53 Comments
ISO is fundamentally the sensitivity at which your cameras sensor reacts to the light when you open the shutter
ISO is measured in a scale (On standard digital cameras) called ISO. ISO is the number indicating a digital camera sensors sensitivity to light, the higher the sensitivity, the less light is needed to make an exposure. It is very helpful to be able to control ISO when taking pictures, let’s use the following example:
I’m at a party, inside a house at night, not much available light apart from a few normal house lights / lamps etc, I want to take a picture of my friend sitting on the chair. So I point the camera at him, press the shutter half down and look at the camera readout – it tells me that that I can properly exposure. the picture (NOT using a flash – assume it’s broken for now) with a shutter speed on AUTO which shows to be 1/15 (One 15th of a second) – I take a picture and check the display, hmn, all blurry. I Check the ISO on the camera… it’s ISO 100… .
Right, so we can see the problem here is that we need to be able to use a faster shutter speed to control some of that blur. But if we just set the shutter speed to be faster, we will be letting in less light – so the although the shot WILL be sharper and less blurry, it will be much darker, much more under exposed.
So we need to increase the shutter speed to say 1/125, 125ths of a second will make sure that the shot is sharp and not blurry (This is dependent on focal length too – but that’s for another day) but somehow keep good exposure… so in this instance we would want to INCREASE the ISO, from ISO 100 to say ISO200, so the sensor will now react twice as fast to the light – giving us an effective double amount of light.
So, take the picture again and have a look at the display, did you manage to get the shot? Was it exposed enough? If not, increase the ISO again to ISO 400 and take another shot.
So why not just slap the ISO up as high as you can to get the sharpest picture possible?
This is because (dependent on how good the camera is) the HIGHER the ISO, the more ‘grainy’ the picture looks, grain is best avoided. You’ve all seen them, images of your friends taken in low light conditions, but all ‘grainy’ or ‘noisy’ as it’s also called. Ideally you want to have the ISO set as low (low being the ISO100 end) as possible to get the shot you need – but sometimes it is just not possible to get the shot you want at such a low ISO. Most compact cameras will set the ISO automatically, but some do give you basic control – all digital SLRs have full control over ISO.
Here is a quick overview of each ISO level:
ISO 100 and lower - Excellent quality for brightly lit places, such as in bright sunlight outside. Allows for lots of detail and great image quality.
ISO 200 - Should be generally be used on dull days such as overcast and cloudy, only a tiny bit of noise
ISO 400 - Great for indoor photography for flash and no flash – best use for high speed photography – but noise can be seen.
ISO 800+ Only really used effectively on high quality digital SLR cameras, most shots taken like this with a small compact camera will look extremely noisy.
I will talk about how to control noise in another article, and also about the relationship between ISO, aperture and shutter speed.
Summary
So remember, the higher the ISO number the quicker the sensor reacts to light – thus giving you effectively MORE light to use – BUT the trade off is increased noise / grain.
If this has been a help to you please leave me a comment, it’s always appreciated – Thank you.
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53 Responses to “What is camera ISO? Help with digital ISO with this simple guide – Digital and film ISO explained”
Leave a Reply
Tags: camera iso - digital camera iso - digital cameras iso - digital iso - film iso - iso - iso 100 - iso 200 - iso 400 - iso 800 - iso100 - iso200 - iso400 - iso800 - what is iso
October 27th, 2007 @ 9:28 pm
Another useful bit of info.. thanks..
May 26th, 2008 @ 3:04 am
great tip! i just bought my camera and was searching for details about iso and got directed by google here
i tried the suggested tip and the result was fantastic
thanks
October 12th, 2008 @ 8:11 am
That was a good information. I just purchased a new D40 (Beginner’s digital SLR) and played with 200 IS and HI mode and could see the difference in dim light.
Thanks for the tip.
November 4th, 2008 @ 4:57 pm
thanks for the information, I was looking at buying a camera with the highest ISO possible to be able to take night shots – good thing I did my research!
December 30th, 2008 @ 9:06 pm
its really helpful for beginners like me .keep up your good work.and share it with us
March 19th, 2009 @ 10:42 pm
thanks for the info. Well written with examples.
May 11th, 2009 @ 6:01 pm
Thanks really appreciate your help…
But what happens if the flash is working then do i need to only mess with shutter speed and not the ISO?
thanks alot your a big help!
May 30th, 2009 @ 7:33 am
Thanks for the information and guidance regarding ISO .
Regards
Inu
June 4th, 2009 @ 7:15 pm
Excellent explanation/example! Needed to read it just the once to absorb the infomation presented before me. Thank you very much for sharing!
June 6th, 2009 @ 5:16 am
exelente ,graciias
July 31st, 2009 @ 8:38 pm
Nice and simply explained, great to find someone who doesnt over complicate things.
August 1st, 2009 @ 10:35 am
Thanks for the kind comments!
August 1st, 2009 @ 10:44 am
“But what happens if the flash is working then do i need to only mess with shutter speed and not the ISO?”
Mohammed:
The flash will help you add more light to the scene, but depending on how you use will affect whether you need to adjust the settinsg further – it’s not a yes or no answer.. if you can light the scene how you want it to look, then yes, you can decrease the iso to account for the added light… it really depends on what you are trying to achieve! Did you have a real world situation where this happened. For instance I was shooting a wedding last week, where the inside of the building was very dark – shooting the first dance, although I had a large flash which lit them up perfectly.. I still needed the high iso and dragged shutter to help expose for the background – rather than them dancing in a big black hole!.. with the flash speed making them sharp… if that makes sense!
August 1st, 2009 @ 10:45 am
Amanda:
Yes having a camera that has better ISO capabilities is certainly a good selling point for a camera, as it gives you more option in low light situations.. but then buying a better lens that lets more light in is also does the same!
September 30th, 2009 @ 12:53 pm
Good tips. Really learned a lot quickly.
October 18th, 2009 @ 11:50 pm
Glad it helped! Thanks
November 5th, 2009 @ 12:09 pm
g/day
thanks for the info,good stuff
regards les
January 22nd, 2010 @ 6:48 pm
Great great articles friend. Good wishes for your well being, health and happiness. Keep it up.
April 5th, 2010 @ 1:10 pm
hi !!
g8 tip….
helped me lot to know abt ISO…
Thnx
April 22nd, 2010 @ 8:53 am
gr8 man..vry helpful..i ws very confused abt it..!!
May 31st, 2010 @ 1:29 pm
I am still confused because my digital camera manual says that a higher ISO will mean less blur. Fine with me, but I don’t understand why. If a higher ISO let in more light and was more sensitive to noise, wouldn’t it show MORE blur??
Anyway, the camera also allows me to decrease the shutter speed to let in more light, but not increase it. Not sure why, because for action shots, it seems to me you’d want a faster shutter speed. But again, they recommend increasing the ISO instead to cut down on blur. And again I ask, why would more sensitivity to light and other images mean less blur?
May 31st, 2010 @ 3:41 pm
Hi, thanks for stopping by.
Right, what they are getting at here, is by increasing the ISO it allows you to use a higher shutter speed, which, in turn, allows you to freeze motion that little bit better. So telling the sensor to react twice as fast, by changing the ISO from lets say 200 to 400, you are allowing the same amount of light to react twice as fast on the sensor, so if you had a combo of ISO 200, f8, 1/100th second, then by increasing the ISO to ISO 400, you would be able to have a combo of ISO 400, f8, 1/200 second. so by increasing the ISO you have enable to use twice as fast shutter speed = less blur.
Hope that makes more sense!
Thanks,
Chris
May 31st, 2010 @ 11:18 pm
actually, it does!!! wow, thanks for getting back to me so quickly. i didn’t expect that. so the iso is increased in reaction to wanting a faster shutter speed in the first place. that makes sense to me.
i love your photos!
May 31st, 2010 @ 11:22 pm
Great! I’m glad it makes sense. Thanks!
Glad I have helped, Kind regards,
Chris
June 1st, 2010 @ 1:10 am
actually now i still have a question…let’s say I set my camera at a high shutter speed to capture a fast-moving image. I then also try to set the ISO high to prevent blur and let in as much light as possible at that speed. Will setting it high cancel out the shutter speed to begin with? And will it not always make a diff anyway because there’s only so much light that can be let in if the shutter speed is fast? why wouldn’t you always want as high an iso and as fast a shutter speed as possible, to prevent blur?
June 1st, 2010 @ 9:32 am
The reason you don’t want high ISO all the time is that introduces grain / noise into the image, which some people see as a negative point for images, so this is where more expensive cameras come in, for instance on my old Canon 40D, ISO 1600 was just too noisy, wheras on the 5Dmk2 ISO 1600 is usable for most images.
There is always a cut off point on each camera at which ISO becomes too much of a distraction (for most people) in an image.
What you should do is take an image of the same object at ISO 100, 200, 400, 800, 1600 and see for yourself exactly what’s going on!
Thanks,
Chris
June 1st, 2010 @ 12:30 pm
Thanks! I am sending a big hug of thanks across the ocean to you.
I feel like a smarter photographer now.
August 25th, 2010 @ 2:08 am
I’ve been experimenting with my digital camera for weeks now, and I find this post helpful. It’s very easy to read and understand. Thanks!
April 12th, 2011 @ 10:25 pm
Thanks from russian.
April 28th, 2011 @ 5:54 pm
It is really great tip. I would like you to explain more about the basic of using camera.
Thanks
May 3rd, 2011 @ 6:37 pm
Great article! I’m a beginner photographer and this helped me learn a lot
…
May 23rd, 2011 @ 6:11 am
I am a beginner.I loved it.simple and straight.thank you.
May 29th, 2011 @ 2:39 pm
Very informative. Thank you.
June 2nd, 2011 @ 11:34 pm
me being a amateur this is really helpful.
Thanks mate
June 4th, 2011 @ 10:45 pm
Excellent practical explanation.Really appreciate your work.
Thank you
June 11th, 2011 @ 11:17 am
Thanks, very helpful
June 24th, 2011 @ 8:33 pm
You answered what I needed to know about ISO quickly and left out needless talk. The topper were the examples that you gave and a summary at the end of best ISO to conditions. Thanks!
July 6th, 2011 @ 3:28 pm
Very helpful….Thanks!
July 9th, 2011 @ 10:10 pm
I’m not a dummy anymore
July 19th, 2011 @ 4:37 am
I am an absolute novice regarding cameras. Just trying to do a little research for the camera my fiance, who knows a lot, is interested in purchasing. Your explanation was extremely clear to me. Thanks so much.
August 7th, 2011 @ 6:25 pm
Thanks for the tips! I just got my Canon 60d and there’s so much to learn!
August 13th, 2011 @ 11:32 am
thanks a lot. I always wanted to experiment with camera settings, but didn’t know where to start. Now i can begin.
September 2nd, 2011 @ 10:33 pm
Thank you!!!
September 30th, 2011 @ 3:54 pm
I really didn’t have a clue about this before! Thanks for the information.
October 21st, 2011 @ 11:51 pm
Thanks so much, answered all my questions!
October 24th, 2011 @ 6:34 am
wonderful, thank you
November 4th, 2011 @ 1:24 pm
this was easy to understand many thanks. I wish I checked befroe I went on the cruise.
November 13th, 2011 @ 10:50 pm
Thank you ever so much for this. Only been doing photography for a year and I’ve been avoiding dark images because of not understanding ISO. Ace!
December 13th, 2011 @ 10:24 pm
Thank you for your sharing, very helpful
December 15th, 2011 @ 11:58 pm
Thank you for the detailed description provide in full on this topic! I greatly appreciate it and will return to read more of your blog tips in the future!
December 20th, 2011 @ 5:07 am
Thank you that was a bit of help
January 6th, 2012 @ 5:20 am
Thanks for explaining this to a photography newbee!
January 19th, 2012 @ 11:08 pm
I have a SLR camera that is over ten years old, I am retiring in a few years. And in saying that, I am thinking about buying the Cannon EOS Rebel T3i, I have read some gook reviews on this camera what do you think, your opinion would be greatly appreciated.