The Camerazzi Community

Understanding and using your camera

Understanding and using your camera

By Mike Harvey
(with a little panelbeating from Pikkie)
Trying to make you make sense from the camera lingo and all those confusing settings…

1.Shooting Modes

Auto Mode
As far as I’m concerned, the reason for the auto mode on a camera is to test that your camera works; or in the rare event that the shot did not come out the way you expected it, to check by using ‘Auto’.
Look at it as a self test mode.
There are no secret police that will pay you a visit because as a beginner you dared to use your camera off auto and that only the chosen togs are allowed into the haloed grounds of manual, aperture or shutter mode…

Program mode
This varies from camera to camera but basically it is the advanced mode of auto.
It still sets the aperture and shutter speed automatically but some functions can be adjusted within preset parameters e.g.: you may set ISO to manual or adjust aperture/shutter with the small +/- scale next to the P in the viewfinder. This will add or remove exposure (light) to or from the auto settings to make your photo lighter or darker. This may still not give a desired result, so on to the next modes…

Aperture and Shutter priority modes (Av and Tv)
By using A or S mode we set the one component (aperture or shutter speed) to a fixed setting and let the camera adjust the other one. When learning to shoot in these modes, it is recommended that you set the ISO to fixed number – in good lighting, set to low number like 100 and leave it there, maybe up to 200 if the light is a little less)

When to use Aperture Priority: When you require a specific aperture for deep or shallow DOF (depth of field). A big aperture (small f-number) like 2.8 or 3.5 let in more light, but also makes the DOF shorter – meaning that a shorter distance inside the image will be in focus. To get a deep DOF (longer distance in focus), use Aperture priority and set aperture small (higher number) like 11 or 16. (See the explanation of DOF lower down.)

When to use Shutter priority: When you require a fast shutter to freeze action like running water, children, horses, athletes; speeding like bikes, cars, trains; flying like birds, planes – use shutter speeds of 500 to 2000 (1/500 sec to 1/2000 sec) and let the camera set the aperture.

Use shutter priority also to prevent camera shake especially on longer zoom lenses e.g. shooting with an 18-200 zoom lens set at 50mm, the shutter speed should not be slower than 1/50 sec and zoomed to 200mm, the shutter should not be slower than 1/200 sec

As a general guideline, Aperture priority is better for close-up shots and portraits where you want to control the DOF (depth of field) and that Shutter priority is better for action shots and landscapes to control movement and camera shake.

2. ISO and using Auto ISO

The ISO-number indicates how sensitive the sensor (ccd) is for the light that falls upon it. When set to a low number (e.g. 50 or 100) the sensor is less sensitive than when set to a high number (800 or 1200)

In the film days, a roll of film had a set ISO that could not be changed – you had to finish shooting all the frames at the same ISO. Today we can change the ISO for every shot if so required, but everything that is possible is not necessarily sensible…

The ISO-setting makes the sensor more sensitive to light. For instance with our 18-200 lens zoomed to 50mm and using aperture priority; shooting a mother holding her baby – You set the aperture to f11 (smaller aperture) to get both mother and child in focus (deeper dof) but this setting causes the shutter speed to fall to 40 (1/40 sec). This is too slow to keep the camera still handheld and a tripod may be impractical… Even if you do use a tripod one of them will probably move… so, lifting the ISO to say 400 makes the sensor more sensitive so you can keep the F11 aperture, and set the shutter faster to say 1/125 sec which is fast enough for the lens and to freeze the subjects and prevent camera shake. The rule of thumb for ISO is: the lower, the better.

Auto ISO
We can set ISO on auto too, but this will cause the camera to auto adjust ISO anytime to meet neutral exposure without changing the shutter speed. If you are using aperture priority mode you can see this effect by adjusting the f-stop, the shutter speed and/or ISO will change. This might not be what we want as we want to exhaust the shutter speed possibilities first, before adjusting the ISO. I prefer to leave ISO fixed, lowest is always better. Only when the shutter speed drops below the zoom setting i.e. 18-200 lens set to 50mm and shutter gets to 1/50 or slower, would I change the ISO upward to get a faster shutter speed. If I can still open the aperture more to get the faster shutter, I will do so before upping the ISO. This would apply to shutter priority mode too: if I needed 1/30 sec to get the motion blur that I want and have to have an aperture of f8, I would move up from my base ISO of 100 until I get an f8 aperture setting.

The bottom line is: only if you exhausted all the possible working combinations of aperture and shutter speed, then step up the ISO.

Manual plus Auto ISO
There is one other mode setting that is not provided as a quick setting like A or S and that is in Manual combined with auto ISO. In this case you set both the aperture and shutter speed manually, but leave the ISO on auto. This will only work in given lighting conditions e.g.: a portrait shot using a candle as the light source. You want f8 to keep everything sharp and you want the shutter speed around 1/125 to keep motion blur out. The auto ISO will probably jump to 6400 or higher to correctly expose the scene. However you will end up with a correctly exposed shot that now looks like Lego land (lots of noise). Not great, so how do we fix this? only thing we can change is to set iso to a fixed setting let say 200 (take it off auto ISO). But now we may need a shutter of ½ sec. This is very slow and not going to work hand held. So we need to add tripod and hope model does not move.

3. Noise and dust

High ISO causes noise. This used to be called ‘grain’ in the film days – speckles or small dots all over the picture. On film it was the result of the crystal structure of the emulsion on the film making the picture look ‘sandy’. Today the ‘noise’ is caused by the sensor becoming too sensitive and picking up both desired and undesired energy. Compare this with an amplifier of which you keep turning up the volume while not playing anything and hear the ‘noise’ it makes.

Another problem with too high ISO, is dust. Look inside a TV set – it is full of dust, the reason being lots of static electricity that attracts dust, so why turn your sensor into a dust magnet?

4. Aperture

About those funny aperture numbers (f-stops)
This is a strange thing for most new togs. You have all these weird numbers and the smaller the number is the bigger the aperture is but the shallower the DOF gets WHAT!!!

OK, as some people would like to understand the ‘why’ behind these numbers, I will try and explain the technicalities as simple as I can:

The whole thing has to do with the ratio between the diameter of the aperture (opening) in the lens and the focal length of the lens e.g. when the diameter of the opening is 25mm on a 50mm lens, the F/stop is 50/25 = f2. If the diameter is 12.5 mm (smaller) on the same 50mm lens, then the f-stop is 50/12.5= 4, so f4 is smaller than f2 – logical?

From this you can also see that if the aperture diameter is 25mm (f2 on the 50mm) and you zoom the lens to 100mm. The f-stop will now become 100/25 = 4.
So, the size of the aperture stays the same, but the f-stop number changes. The f-stop does not measure the size of the aperture, but the relation between the aperture diameter and the length of the lens.

While we are at it, let’s complicate it a little more: There are certain ‘standard f-stops or full-stops where the next stop is half the size of the previous one, so it lets in only half the light of the previous one. These ‘full f-stops’ are 1.0, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0, 32.0. Because the amount of light that reaches the sensor depends on the surface of the opening (aperture) and the surface is calculated with the pi r square formula (can’t find the symbol on the keyboard), every next f-stop number is 1.4 times the previous number, but one half of the surface. In common English: If an f-stop of f4 lets in a certain amount of light, an f-stop of 5.6 will let in only half that amount and an f-stop of 2.8 will let in twice the amount of light. Every time we multiply the f-number with 1.4 the amount of light halves because the surface of the aperture (opening) is half e.g. 2.8 x 1.4 = 4 (rounded off) and 4 x 1.4 = 5.6

For those who do not make out the mathematics… it is maybe just easier to remember that the lower numbers are the bigger holes and lets in the most light. They can make you over-expose a photo and also makes the DOF very shallow (see below about dof).

Higher numbers are the smaller holes and lets in the least light. They can make you under-expose a photo and they have a deep DOF.

Lenses (especially long zoom lenses) starting at a very low f-stop (like f2.8) are called ‘fast’ lenses because they let in a lot of light, (so you can use a faster shutter speed) but they are heavy to carry, expensive to make, and very expensive to buy.

5. Shutter speed

This is pretty easy – the time that the shutter stays open and light falls on the sensor.
Base time is 1 sec then you divide by 2
1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128 (125), 1/250 etc.
These came from film days and were pretty much the available shutter speeds.
Now with digital we can add metric to that
1/250, 1/500, 1/1000, 1/2000, 1/4000.
The faster the shutter speed, the less light will fall on the sensor, but we need fast shutter speeds to freeze movement. When a subject moves while the photo is taken, the photo will be blurred (motion blur) and the same happens when the camera moves (camera shake). A Fast shutter simply outsmarts these movements – the only problem is that we still need enough light to get a good picture and a fast shutter reduces the light.

6. Exposure

Exposure is the amount of light that falls on the sensor. The exact amount is determined by the combination of the shutter speed and aperture (f-stop). If the light is too much, the photo will be too white (over-exposed) and if it is too little, the photo will be too dark (under exposed). So the object of all the f-stop and shutter speed talk is simply to find the right combinations for different situations to expose the pictures correctly.

7. Depth of Field (DOF)

DOF (depth of field) is the distance (front to back) of a photo that is in focus. Deep or long DOF means that a long distance inside the photo is in focus and shallow or short DOF means that a short distance is in focus. Short DOF is mostly used to isolate the subject from the background by getting the subject in focus and the background out of focus. Some other photos like landscapes require long DOF to get everything from front to back in focus.

The DOF is determined by the camera-to-subject distance, the lens focal length, the lens f-number, and the format size or ‘circle of confusion’.
“Right I know exactly what you just said…”
Ok let me try and explain:
Let’s say you shoot with a 50mm lens set at f8 (aperture priority) and the subject is one metre away, it has a DOF of 200mm. If you get closer to the subject, say to 200mm instead of one metre, the DOF will drop from 200 mm to about 40mm. So the closer you get the shorter the DOF gets. To keep the DOF long (200mm when the subject is only 200mm away) you need to increase the f-number (make the aperture smaller) to about F32 or higher.

Because the DOF becomes shorter the closer you get, has a great influence in macro photography where you get very close to the subject and the DOF gets very short – that is why true macro lenses have very large f-number (some as high as f64) and are normally around 100mm or longer – all this to try and get longer DOF!

If you guessed from the above that a smaller aperture (higher f-number) helps to get longer DOF, you are 100% correct. Bottom line: for long DOF use small aperture (high number) and/or get further away; for short DOF, use large aperture (small number) and/or get closer.

8. Synchronization

Sync speed is the highest shutter speed that you can use when using flash. So, what does the shutter speed have to do with the flash? Basically that the flash has to fire while the shutter is open to get the extra light into the camera. If it fires before the shutter opens or after it has closed, the extra light is useless…logical?

Just figure this: From the time you press the shutter the signal has to go to the hot shoe then to the trigger then to the receiver then to the control circuit and then to release the energy, then the light has to travel to the subject and bounce back to the camera through the lens and land on the sensor. This does not happen instantly. Although the flash itself is very fast, the process takes time, and while this is all happening the shutter is doing its own thing it waits for no one.
So that is why we need sync speed; to make sure everybody is on the same page – you, the shutter and the flash.

In the film days with its mechanical shutter releases most cameras synchronised at 1/60 sec and maybe up to 1/125 sec. Today we can sync up to 1/500 (Nikon D70)
But most cameras stop around 1/250. The non slr’s with complete electronic shutters can actually sync at higher speeds than the slr’s

Must I use the highest sync speed to get the best shot?
No, only if the ambient light is high enough to affect the exposure e.g. studio setup: I take a light reading and get a correct exposure (no flash) at F8 ISO 100 (this I pre-set) and exposure is 4sec. So shooting at any shutter speed of 1 sec or faster the picture is going to be black in any case as it will be at least 3 seconds under exposed. So it will really not matter if I set my shutter speed to 1/60 or 1/125 or 1/250 it will have no effect as in all cases the photo will be black and only the light from the flash (that lasts only 1/2000 sec) will be recorded.

On the other hand if I get a reading at f8 ISO 100 of 1/125 sec and I shoot at 1/60 sec with flash, the ‘normal light’ as well as the flash light will be captured, in which case I need a faster sync speed (like 1/250 sec) to eliminate the influence of the ambient light.

Sometimes we do actually want to use the ambient light as well as the flash light, for instance when shooting a person against the bright sky or other light background, in which case it is good policy to meter the light on the sky (background) to expose that correctly without the flash. This will make the face too dark and the flash is then used to fill the face with light (fill flash). Doing this it is always better to shoot in shutter priority and set the shutter to a speed that will sync correctly.

The actual duration of the light from any decent flash gear is very short like 1/2000 sec. So there is no danger that the shutter will be too fast for the flash – just a matter of making sure that 1/2000 sec of light happens sometime during the 1/250 sec that the shutter is open. I find around 1/125 is a good sync speed, though some togs are bent on shooting at the highest possible sync speed.

Controlling exposure with flash
Because the flash is so much faster than the shutter, there is no way that the shutter speed can control the amount of light from the flash that will fall on the sensor. The only ways to control this other than setting the aperture (f-stop) is to step down (or up) the power on the flash – most proper flash units can do this and TTL flash units will do it automatically. Alternatively one can make some plan to diffuse or reflect (bounce) the light from the flash.

9. Light Metering

We have three basic forms of metering light, no matter what it is called (different camera manufacturers give them different names)
Overall metering
This takes the average light of the whole view and finds a happy balance and that is what you get, a happy average. It works well most of the time – kind of like AUTO, but kind of falls down in big light difference shots, like sunsets where you leave the sun dead centre. (its is never a bad idea to move it to a corner and see what happens.)
Centre weighted metering
This puts most of the exposure importance in the centre third of view in kind of an egg shape on its side. This metering works best if the sun is off to one side it is not the major light source for metering.
Spot metering
That is exactly what it does – it meters the spot you focused on. This is the setting my camera lives on, because what I focus on is what I want correctly exposed. I will go off the spot of focus sometimes to check a few other places in the shot to see what I have and then adjust manually from what I got e.g.: Late afternoon, model’s back to the sun. The sun is behind her head. With spot metering I am metering on and exposing for her face – that’s what I focused on. With centre weighted metering the reading would include some of the bright light from behind and she would be darker. With overall metering, she would be a silhouette as my average light is much brighter than her face and the camera will reduce the exposure accordingly.

10. White Balance

Setting the white balance on your camera boils down to setting the colours in such a way that the whites will actually be white and not blue-white or yellow-white or some other white. As you know the colour of the light in which we are shooting changes all the time – clear sunlight is a different colour from overcast light, from early sunrise light, from light bulbs, from fluorescent tubes, from your flash light from street lights, from a candle….whatever.

Our eyes do not really make a distinction when we look at a white wall in any of these different light situations, as our brain keeps telling us: ‘that is white.’ Yet somehow it can look quite wrong if the white wall in a picture appears to be blue-ish or yellow-ish.

The white balance will of course not only set the whites, but all the colours in the photo are ‘balanced’ for the whites to actually appear white. As we often want a specific colour cast like yellow or blue in the photo, many togs will experiment shooting at the ‘wrong’ white balance to get a specific light effect.

My advice: Leave the white balance on auto! It gives you one less setting to worry about, and if the colour is wrong, it can easily be corrected in post processing, especially when shooting in RAW

11. How many megapixels?

The word ‘pixels’ are short for ‘picture elements’ and ‘megapixels’ refer to how many millions of these elements make up a photo (12Mp = 12 million pixels). The camera sensor (or ccd – the plate that registers the light coming through the lens) is made up of millions of very small light detectors each one capturing the light that falls upon it and changing it into an electric impulse. Eventually the combined picture we see on the screen or on paper also consist of little squares of colour (pixels) but because they are so small, the eye perceives it as a smooth image where colours change gradually.

So, the more megapixels you have the better the photo quality like the salespeople tells you? This is a tricky one! On one side we want as much information gathering ability as possible (more megapixels gathers more information) but this does not always help to improve the quality – you can only get so much elements in a given size before it becomes over-crowded.

It is also true that a small 10Mp p&s will not produce nearly the same quality as a 10Mp dslr – same number of megapixels but those of the p&s are crammed onto a smaller sensor and even made smaller to get them to fit with resulting ‘noisy’ images and general lower quality.

Another thing that matters more than the number of megapixels, is the engine that does the work of sorting out the info the ccd received. Look at it this way: you have a 10 million bricks (pixels), how do you get to build your mansion? Get a bloke on the side of the road or a master builder? I know who I am going for. So again 10 megapixels in a 2cent point and shoot cannot match a R50000 pro camera also with 10 megapixels as the pro-camera simply processes the data so much better.
There are more factors influencing the quality like lens quality (good glass).

Since none of our monitors are able to show even half the number of megapixels recorded by a 10Mp camera, the difference between a 3Mp and a 10Mp image on the computer screen will hardly be noticeable, but there will be a very noticeable difference between the 10Mp p&s and the 10 Mp dslr photos.

12. Conclusion

Did this make it any easier to understand your camera? Maybe not, but rather aim at solving one of these puzzles/mysteries at a time and then move to the next one.
Now you also know why the owner’s manual made no sense either….

Is it not easier to just leave it on auto? YES but were is the fun in that? Nothing beats that once in a lifetime shot where unfortunately all the settings were wrong! But at least it was you who made the mistake and not the camera.

Well, this made sense to me when I typed it, but if you find any confusing parts, let me know and I will try and explain it better

Mike