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TOPIC: Basic Photography Concepts

Basic Photography Concepts 5 years 1 week ago #11304

  • timwatts
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JOEL SUGGESTED SOME TIME AGO THAT I PUT THIS AS A STICKY SO HERE IT IS.....

BASIC PHOTOGRAPHY - a 'brief' note (!) written by tim watts while bored off my tits one nightshift!

It actually helps to think of an old film camera for a moment.

You had a lens letting light through a little hole and you exposed the film to the light (the image) passing through this hole for a certain amount of time to make a photo. Different films reacted faster or slower to the light.
so the variables are:

1) The size of the hole. (aperture)
2) How long the shutter is open. (shutter Speed)
3) How sensitive the film is to light. (ISO setting)

Digital cameras have exactly the same three settings.

Thats is - it really is as simple as that.

The 'trick' is setting them all correctly for a given situation.

Make the hole too big and/or open the shutter too long and/or have the ISO too sensitive to light and the picture is totally over exposed - completely white!

Hole to small, shutter opened and closed very quickly and iso not sensitive enough and you take a nice black photo of fook all!

So the 'trick' is to balance these three settings to get a correctly exposed photo.
Obviously this will change based on it being taken in a dull room, or a brightly lit sunny day. Or do you want the cloudy sky exposed correctly or the persons face that happens to be in shadow?

Auto: You can put your camera in AUTO and it will pick settings to try to do all this for you – but at the end of the day it doesn’t know what you are trying to do from a creative point of view.

A setting is aperture priority. This means YOU set the aperture and the camera works out the rest.

S setting is Shutter priority. This means YOU set the shutter speed and the camera works out the rest.

M is Manual, you have to do everything!

Lets forget Auto, A and S modes (think yours may also have a ‘scene’ mode, we’ll forget this for now too).

Obviously in M manual mode you need to make a decision on which one of the three settings you want to start setting first and then bring the others in to match. Other than obtaining correct exposure there is obviously other choices to make.

1) The Size of the Hole (aperture): Small hole = large depth of field (and vice versa). Imagine a shot where you've focused on someones face close to the camera, but you want the background (further away) to be blurred. This is achieved by a large hole, large aperture.

like this: (Shallow DOF, small f number, (big hole!)

shallowdof.jpg


See the way the trees in the background are totally out of focus but thats a nice effect and makes the subject 'pop' into the picture.

Alternatively, you might want to ensure that the near to camera subject and the far away stuff is all in focus – you’d now need to use a large aperture.

like this: (Large DOF, Bigger f number, (small hole!)
great_depth_of_field_in_landscape_photo.jpg


Obviously adjusting the aperture to achieve the effect you want will have a knock on effect to the other 2 settings.

So, Aperture effects DEPTH OF FIELD ‘DOF’ – have a primary concern for Aperture if the depth of field of the focus is of prime importance for your photo.

Aperture is expressed as an ‘f’ number. The confusing this is that its arse about tit. i.e. small ‘f’ number = large hole and vice versa. Just remember:

Small f number = big hole = more light = less depth of field (and of course the opposite!)

Small f number of say f1.4 might literally mean that the ‘in focus depth of field’ might only be a few mm. i.e. the tip of someones nose might be in focus but their eyes might not be, Somewhere about f2.8 this get a bit bit more sensible and then f8 and above starts getting good for landscape shots where you want it all in focus.

2) Shutter speed is measured in seconds 30" 10" 2" 1” etc or more commonly in fractions of a second 1/4" 1/10" 1/100”, 1/1000” second etc.

Other than obtaining correct exposure, shutter speed is predominantly concerned with freezing movement (or sometime creatively NOT freezing movement).

Think water flowing down a water fall – Sometimes you want to freeze the action, every individual droplet of water frozen perfectly sharply. like this:

Fast shutter:
AbstractWater4.jpg


Or sometimes you want it to appeared blurred to give a different effect like this:

Slow Shutter speed:
dsc_4343.jpg


– same idea goes for shooting sports, or anything that moves. Sometimes ‘action’ blur is desirable, sometimes its not. Its simple to think about really if you take a picture of a moving car on a 10 second exposure its going to be blurred like hell coz its moved a long way in ten seconds!

Shutter speed is obviously also linked to how the camera is held. i.e. movement! If you are shooting at a very high shutter speed you can be waving the camera around your head when you hit the button and it will still freeze the shot and you'll get a sharp picture, shooting at a slower speed and you'll be hard pressed to keep the camera still enough to get a sharp shot at all.

I'll talk about lens length a bit later but imagine you've got two broom handles, a very long on and a very short one. Try to hold the long one horizontal in front of you. You'd do well to prevent the far end of it moving around. In fact if you measure how much it was moving it would probably be measured in several cm's of movement.

Do the same with a short broom handle and the distance the tip would be moving around might only be a few mm.

Its like a lever - the further along the lever you are, the more movement there is.

A 'zoom' (telephoto) lens is like this. They are defined in mm. Smaller ones being a wider lens and larger ones being more zoom! Obviously a tiny movement when using a very powerful zoom lens translates to a large movement in terms on what you see going on through the view finder.

A rule of thumb for hand held shots is to use a shutter speed equal or faster than 1 divided by the lens length in mm.

So for a 50mm lens (or a zoom lens set at 50mm) set to 1/50th of a second or faster for hand held

For a 100mm lens 1/100th of a second or faster.

If you want to go slower than this you really need to be using a tripod.


3) ISO Really is a ‘fudge’ factor. Creatively the only two settings you really want to worry about are the aperture (f number) and shutter speed. What ISO allows is a bit of a fudging of the exposure.

Lets say you want to freeze the droplets of water in a waterfall on a very dull overcast day, and also that you want to retain a decent depth of field (front to back picture sharpness. Your going to need a fast shutter speed to freeze the movement and also a small hole (aperture) to retain the sharpness (large depth of field). These will mean that the ‘film’ is not exposed to much light. You fire off a shot and its really underexposed as expected. What do you do? Well, you either increase the shutter speed or increase the hole (smaller f number) but then you lose the effect you are after. Not good.

What you can do is increase the ISO setting of the camera. This makes the ‘film’ more sensitive to light so that you now get a better exposure. Even with a small hole, fast shutter.

The downside of increasing the ISO is that the picture gets more ‘noise’ - nasty grain and silly coloured dots etc.

Taken to extremes it starts to lookas bad as this type of thing!:
B00643.jpg


Modern half decent SLR’s are actually very good at increasing the ISO without putting too much noise in the picture but as a rule the lower the ISO setting you can use, the better quality the picture will be.

Anything between ISO-100 (normally the lowest setting) and ISO-800 should give good results, going higher its really dependent on the camera to be honest. Just remember use ISO-100 if possible and only increase if you need to. Lower is better.

But that said, its there to be used just don’t go too far with it!

--

So, you’ve got an idea now how your basic settings work and effect things.

Obtaining the correct exposure is an art but the camera makes it easy for you because it will automatically ‘meter’ the exposure.

You’ll have a display somewhere which when you half hold the shutter button down will give the a + or – scale of some sort – ‘0’ being in the middle suggesting correct exposure (obviously this is a guide and it depends if you have the camera metering the whole picture as an average or want the exposure metered of a specific area – i.e. just a face.

--

Lenses and focus:

– first of all – you’ve got whatever lens you’ve already got and you might confuse yourself reading this!

You’re likely to have a standard 'kit' lens and its very likely to be something like a 18-55mm Nikkor f3.5-5.6

In really simple terms, The mm bit is the ‘zoom’ of the lens. Smaller 18mm number here gives a wider picture (will fit more of the view in), the larger number 55mm is the amount of ‘zoom in’.

A super wide 10mm gives (getting on for) 180 degrees of view whereas 500mm would be a mega zoom for photographing Joels wadger at 500 yards away after he’s just been wading up the Milwr tunnel for the last hour.

The f part refers to the aperture (you already know what this is!) and it is the maximum size of the hole (i.e. the smallest f number) - (remember f number is inverse of hole size).

So for this lens:

18mm gives wide(ish) view with an maximum aperture of f3.5 (large hole)
55mm give a zoomed view with an maximum aperture of f5.6 (smaller hole)
35mm is obviously somewhere in the middle with a maximum aperture of about f4.5.

It’s a bit of a head fry coz the aperture/f number works back to front. But Just remember:

Small f number = large aperture = more light in a given time = less DOF

As you can see small f numbers mean more light can be fed through the lens and therefore faster shutter speeds can be used.

In general, its harder and more expensive to make longer (mm) lenses with low f numbers (big holes)!

Lenses with smaller f numbers are desirable as they allow faster shutter speeds and better performance in low light. It makes them bloody expensive. Try to price up a 500mm f2.8 lens to see what I mean!

Final point, whatever the f number quoted on the lens at a given ‘mm’ length, remember this is a MAXIMUM aperture (hole size). With all lens’s this can be increased as much as you want with the camera settings.

So with your lens set at 18mm you could choose anywhere from f3.5 to f22 (or f36 or something like that) but you couldn’t use f 2.8 or f1.4 – the camera won’t let you coz the lens isn’t able to do it!

Focus: You’ll be able to switch between manual and auto focus somehow on you camera/lens. There will be various focus modes that your camera works to autofocus – you’ll be best of reading the specific manual for this.

Underground specific:

Lets think about things for a second. For the average scene underground:

1) Nothings moving so Shutter speed isn’t an issue – we don’t need to freeze movement.

2) We generally want everything in sharp focus, things close up as well as far away so we want a small hole (large f number).

3) There is bugger all light.

The easiest way to get into underground photography is to light paint.

So:

1) Set the shutter speed very slow: we’re talking several seconds here – say try 5 seconds first of all.

2) Set the aperture to a small size (large f number – f8 and above)

3) Set the ISO fairly low as we don’t want noise but neither do we want to be spending ages flashing a torch around the place so lets say ISO 200

Lets set focus to Manual mode (it’ll struggle to focus in the dark automatically!), with a large f number its not going to be critical so guess! For most lens it’ll be focused to infinity or there abouts if the subject is more than a handful of yards away when at the wide (small mm) end of the zoom range.

Fire of a shot. Look at the exposure frig the settings from there. i.e. too bright less shutter open time, lower power torch, higher f number, lower iso and vice versa. You’ll really quickly find a combination that works well for your camera, lens and light source.

If you want to start freezing movement (i.e. SRT action shots etc) you’ll have to move on to using flashes radio trigers etc, etc but that’s for another day! :-)
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Tim Watts
Last Edit: 4 years 8 months ago by timwatts.
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