Whoops! This should really have gone up on Sunday…but better late than never, right?
This second lesson of basic photography tips will be covering two elements of light exposure for digital cameras – ISO and exposure compensation.
Okay, lets start with the easier one first.
To understand what ISO is and how it works, we need to go back to the time of film cameras. Remember film? That stuff you buy in rolls, load into the back of a camera, then take to the photo store to be developed, always being excited to see what you managed to shoot? Good, now moving on…
ISO used to be known as ASA, and is a measurement of film speed – e.g. film with a speed of ASA 80 was ‘slower’ than film with an ASA of 400, and each different speed of film was suited to different conditions. The ASA label was changed to ISO some years back, when the system was standardized internationally. Right, so now you’ve got that bit of background, lets move on.
Thinking strictly about digital cameras, what does ISO mean since there is no actual film?
Digital cameras have an image sensor that is exposed to the light (in place of what film would do), and the ISO number stands for the light sensitivity of that image sensor – so a setting of ISO 80 on your digicam will not be very light sensitive, and as a result, should be used when taking photos in brightly lit areas otherwise they may come out too dark.
Many digital point-and-shoot cameras being sold today are toted as having an ISO range of anywhere from 80 to 3600, and like the megapixels battle, seems to be pushing the idea that ‘bigger is better’…but is it really?
Quite frankly, no.
Without getting too much into the technical jibber-jabber, digital point-and-shoot cameras tend to have quite small image sensors, and especially with the increased megapixel count, have millions of pixels crammed onto that tiny sensor – this is one of the key differences between point-and-shoot and dSLRs, the latter tend to have much larger image sensors and (as a result) pixels, therefore they are not as compromising when shooting in low light.
Look at this table below to see what I mean:
|Here’s the scene – some dried beans on my dining room table in my kitchen. It was actually quite dark and this photo is one taken after exposure compensation was applied, but we’ll just be looking at the effects of increased ISO on an image for now.|
|Taken with ISO 80
Here’s a section of that photo at 100% – you can see a little bit of graininess (called noise), but we’re really not doing too badly in that the image is still pretty clear.
|Taken with ISO 100
A slight increase in ISO has resulted in an image which is slightly brighter, the colour looks a teensy bit richer, and there doesn’t appear to be any increase in noise.
|Taken with ISO 200
Okay, so the image is once again brighter, but with the added brightness we’ve got some downsides – careful inspection reveals that there is a considerable loss in fine detail.(Compare the lit area on the bean on the left of the image for the previous photo and this one – see how the edges of that white area have lost some detail?)Also, there appears to be a slight increase in the noisiness of the image.
|Taken with ISO 400
Ewww. The increased lightness of the image has flattened it and lost that sense of depth, and there’s so much noise here that there all sharp definition has been lost.
|Taken with ISO 800
Same problems as the previous image, just even more so. This is pretty awful stuff, and not the kind of image you’d want to try and use.
|Taken with ISO 1600
I never ever use this setting for ANY scene, and this is why. Though this image is being viewed at 100%, even the uncropped photo would be unusable.
I never use a setting higher than ISO 400, and since I mostly shoot my photos in the afternoon, I find that sticking with ISO 80-200 is usually quite a good bet.
Please bear in mind – the less light there is and the less light being allowed to your cameras image sensor, the slower the shutter speed will be. For this reason, an investment into a cheap little tripod is a fabulous idea – you can get little ones that you can pop into a handbag for as little as $10-$15, and using a tripod will mean not having to worry about a case of shaky hands or taking a breath while you press the release button to take that shot!
Alrighty, now that we’ve covered ISO, lets move onto exposure compensation.
Nearly all digital cameras sold today will come with this feature, and trust me when I say that you will come to adore this feature (though you may need aforementioned tripod to fully fall in love with it!). The exposure compensation (technically, exposure value, hence expressed as EV) feature will usually go from -2.0 to +2.0, with each stop broken into halves or thirds (e.g. 0.0, +1/3, +2/3, +1). By increasing or decreasing this value, you are able to exert some manual control over how much light is being allowed through to your cameras image sensor.
Once again, as the actual setup and menu on digital cameras differ from brand to brand and model to model, I can’t tell you where you can find the button to access this particular feature, but you should be able to find it in your cameras user manual (if you’ve lost your manual, try looking for it on the website of the company who made the camera, they should have it available for download). But first, perhaps I should show you why this is such a great feature?
|Awful, isn’t it? This is a photo of the same beans as before, but with all of my cameras settings set to auto, and flash forced off.Way, way too dark, no detail, if you used this image to try and sell these beans, they’d probably never get bought.This is why it is a good idea to learn how to use your cameras settings – auto settings rarely give the best shots possible of a scene.|
|A little better – now I’ve manually adjusted my white balance setting, and there’s a marked improvement. Still not too pretty, and I think we can do better. Time to try out exposure compensation!|
|Why, hallo thar! I’ve increased my exposure value by a third (EV +1/3), and just that has made the image much brighter. Still those shadows are too deep and the beans still rather unappealing. Let’s keep going…|
|I’ve increased my exposure value some more (EV +2/3) and now those beans are really starting to pop – the colour has brightened but we still haven’t lost too much shadow to make the image flat.It’s pretty nice now…but let’s see what happens if I increase it just one more point.|
|Taken at EV +1.0 – Oh my goodness, just look at that! The beans have lost a teensy bit of detail, but in my opinion, I think they’ve gained enough to make it worthwhile – the colours pop more, the beans appear fuller and generally more attractive.
Also notice – increasing my exposure value has brightened the scene but has not increased the noisiness of the image!
(This is also the beginning image for the ISO shots earlier, though you should usually set your ISO then fiddle with the EV)
Generally speaking, you should use higher exposure values when shooting brightly lit scenes or scenes with bright/light backgrounds (such as the white background the beans are on), and lower exposure values should be used in scenes which are quite dark or have dark foregrounds with lighter backgrounds. These are general rules, and you should usually play around with your camera and its settings in each scene before taking your shot as an okay shot can be made gorgeous with post production, but a crap photo will only have the possibility of being made ‘okay’ (and it will usually involve a lot more work in post production!)
Make sure you look at each photo on the screen of your digital camera after you’ve shot it, and if it looks too bright (overexposed) or too dark (underexposed), play with these settings and try and get a shot that you can feel satisfied with. Take an extra minute or two to fire off some extra shots – after all, once the dish has been eaten, you’ll have to make it again to have another shot at photographing it, right?
So, time for you to go off and have a play-around with your camera and practice working in different lighting conditions! If you have any suggestions or questions or found this helpful, please make sure to leave a comment to let me know And be sure to come back next week for the third lesson (which I guarantee will be much shorter than this), when I will be covering how to make the best of your on-camera flash!
[tags]photography, beginner, cameras, point and shoot, guides, ISO, exposure, light, dark[/tags]