• Keith Proven

Controls to Manual

This is going to be my second sort of techie style post. It's really pitched at those of you who are either new to photography, or wanting to get past 'point and shoot' or auto settings and begin to push your creativity.


If you're a more experienced photographer, you could always give this blog the once over and tell me where I'm going wrong or what isn't as clear as it should be! 'Cause if I'm looking to develop to doing some coaching/courses, getting the key info across in a concise and understandable way would be good.

The most important thing you can do creatively to take control of your photography is to shoot in manual mode and, if available on your camera, RAW. To set all the factors that affect how the camera records the image gives you the ultimate say as to how the final image will turn out. And shooting RAW allows you to produce an image file which has not been compressed by the camera's software (an in-camera jpeg takes all the digital information, applies noise reduction and sharpening, colour balance etc, then takes away lots of information to produce a smaller, manageable and easily readable file).


When capturing an image, you are making a record of the light passing through the camera lens and landing on the sensor in the camera body. The sensor is an array of photo-reactive cells that when activated by light landing on them the camera processor converts into a digital image.


First, Let's Talk About the 'f' Word


As well as some terminology related to manual settings, there's a bit of maths and physics that it's helpful to get a handle on to make understanding some camera basics easier.


"f": yes, it's the 'f' word or two words actually. A lower case 'f' stands for focal length. When you buy a lens for a camera, the focal length refers to the distance in millimetres between the centre of the lens (or group of lenses) set to focus at infinity and the camera sensor where the image will be clearly focused. This in turn determines how much of the resolved image is visible within the scope of the sensor and therefore displays the telephoto or zoomed-in quality of a longer focal length lens.



Right, now why are manual settings so important to the final image? Like I said, it's a bit to do with physics and maths and stuff which I'll touch on to avoid confusion. If, like me, you're armed with only a little knowledge, it's far easier to learn what the major determining factors are and how altering them alters the look of an image in practice. I've always found that 'doing' and experience count for a lot when it comes to something as visual as photography.

Initially what you're looking for is a clean, well focussed image, not too light and not too dark and with the main subject of your photograph clearly differentiated from other elements in the foreground or background. Ultimately, once you can do this consistently, you can create whatever look of image you want AND know what to do to achieve it.


The 3 Key Elements


There are really only 3 things that you need to change in order to get a correctly exposed image. However, these things are closely interconnected and work in relation to each other to determine how an image will appear.:


APERTURE (F-Stop, F-number, f/N):

Like the iris of the eye controls the size of a pupil, a camera lens has a group of thin overlapping blades that adjust the size of the aperture and control the amount of light passing through the lens and reaching the sensor by increasing or decreasing the size of the 'hole' or aperture within the lens. If it's really sunny, your pupils will contract so that less light enters your eye whereas in a darkened room, your pupils open up large to allow as much light in as possible. It's the same with the camera lens. In bright conditions setting a small aperture reduces the amount of light and in dull or dark conditions you want as much light as possible to enter the camera so need a large aperture. The fact that as the aperture gets smaller the f/stop number gets bigger has been a cause of confusion for many (me included!). This is mainly down to how the term is written is inconsistent. Always using lower case f meaning focal length and the inclusion of the 'slash', meaning 'divided by', should clarify things. The f number is actually a calculation of the physical diameter of the aperture. A 50mm lens set at an aperture of f/2 means that the aperture will be focal length divided by 2 or 50mm / 2 = 25mm. set the f stop to f/22 and the aperture will be 50mm / 22 = 2.27mm. Easy! A bigger f number makes for a smaller aperture.


Aperture also affects depth of field - or how much focus falls off either side of the focal point. Before writing this blog, I didn't know (or care!) why this happened. I only knew that a large aperture (small f/number) made for a shallow depth of field and was therefore very focus critical and a small aperture made for a greater depth of field - more elements in acceptable focus. So, I decided to read up on it with the intention of explaining why this was the case. When I got to the bit regarding the relationship between the depth of field and the area called the 'Circle of Confusion' I wondered if I was getting in too deep! I'll try to keep it as simple as possible, but if the thought of circles of confusion freaks you out, just skip this bit.


So, here goes:


Basically, the circle of confusion is a measure of the size of an area on the sensor where a resulting printed image of a focused point of light, when viewed at a set size (usually 8" x 10") from a set distance goes from being pin sharp to not quite pin sharp. Anything registering on the sensor outwith the acceptable parameters will appear increasingly blurred. In reality, the circle of confusion is measured in fractions of a millimetre. In the following, hugely exaggerated , diagram, you can see how it affects depth of field.



A wee final footnote on aperture and focus. All lenses have an aperture crisp focus sweet spot, an f/N at which the image is the sharpest it can be. In general it tends to be a couple of stops down from fully open. And certainly, at the smallest apertures (biggest f/stop numbers) the images tend to be on the 'softer' side of crisp.


SHUTTER SPEED:

Again, like aperture, shutter speed will dictate how much light has a chance to hit the camera's sensor. A fast shutter speed means the sensor is exposed to the light for a very little time. This would be appropriate for bright days. On cloudy days or at dawn and dusk, slower shutter speeds would be needed (assuming all other settings remain the same) in order for the light striking the photo-reactive cells to be sufficient to translate into a viewable image.


That one is pretty straightforward. But remember that the 3 variables we are looking at are critically dependent on one another. And each variable has its own specific contribution to an image. While we saw that aperture was responsible for the depth of field of an image, the shutter speed determines how much a specific moment in time can be 'frozen'. If you're photographing a moving subject then a faster shutter speed would be required to 'freeze' that motion. Were the sensor exposed to the image for a longer time, then the subject will have moved across the frame and appear blurred.


For landscapes, or still-life, the shutter speed is less of an issue - with the following caveats: a rule of thumb with shutter speed is don't go for a shutter speed SLOWER than 1 divided by the focal length of the lens unless you are using a tripod. So, for hand held photography using a 50mm lens a shutter speed of 1/50th of a second is as slow as you should really go. With a 400mm telephoto lens, you'd struggle to avoid camera shake at anything longer than 1/400th of a second.


ISO:

The final element in this triumvirate of controlling factors is the ISO, an indication of the "sensitivity" of the sensor. Again, I'm guessing it's really technical and someone could probably explain it to you, just not me. I put sensitivity in quotes because, although you'll hear it oft said that changing the iso changes the sensitivity, a sensor only has one level of sensitivity. Unlike aperture and shutter speed which actually control the amount of light hitting the sensor and therefore have a direct effect on exposure, iso is merely an indication to the processor that the amount of light hitting the sensor is actually more or less than is required for the image output.


iso numbers go from low to high. The 'native' sensitivity will be at the bottom which for my Olympus is 200 iso but for your camera it could be 64 or 100. On a cloudy day, when the light is low, you have your aperture wide open and the shutter speed is as slow as you can manage and still the image is underexposed, you can change the iso, which is basically telling the camera that the amount of light hitting the sensor will result in an image that is darker than in reality. The camera then boosts the signal from the sensor to the processor to compensate, tahdah!


The most important thing to remember about iso is that the further you move away from that original or native sensitivity, the more the amplification of the signal in the camera's processor creates digital 'noise'. This is like the graining on old film camera images - though is usually more distracting.


A last bit of useful info, while it is recommended to always shoot at the lowest iso possible and while modern digital files that are underexposed can easily be lightened in something like Photoshop, it is better to up the iso to get a correctly exposed image than use a low iso and brighten an underexposed image in post.


Example

Just a quick example to show how changing these 3 elements can change the look of the image while keeping the exposure correct.


First I set up a wee scene with a foreground, mid-ground and background element.



Then I put the camera on a tripod and took an image using a 60mm lens, looking through the scene and focussing on the middle element - the nose of the wee wooden cat. The camera settings were: iso200 (my base iso), 1/200s, f/2.8


The background and foreground are out of focus and even the rear end of the wooden cat has lost some sharpness (that'll be the Circle of Confusion for you!).


Next, wanting to get more of the scene in focus while making sure that the exposure remained the same (+/- 0.0), I set the camera to: iso200, 1/3s, f/22


Because I had narrowed the aperture to increase the depth of field, I needed to leave the shutter open for long enough to let sufficient light in. Now, however, the whole of the wooden cat is crisp, the Egyptian cat is pretty clear and the background is becoming clearer.


f/2.8 and f/22 were the two extreme ends of that lens' capabilities. And given the compressed nature of the set up (I was only about 45cm from the scene) I would never be able to get everything in focus.


If you are new to manual settings, I hope this has been helpful. The best thing to do is go out and practice in different situations.

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