Here the are two previous installments:

Photography Basics I | Photography Basics II

Today I take another look at terminology – that is thrown at us at every stop of the way.

IS | OS | VS | VR | Shake reduction ( internal and External)

Abbreviations. Don’t you hate them? The more since all of them mean the same. But – coming
from different companies, they sure have to have their own name.

For the sake of argument I will use IS (Image stabilization) in this post as the term.

Internal? External?

Well – there are basically two methods – one is providing the stabilization within the camera, the other
is to have the technology integrated in the lens. In most cases it is achieved by a floating lens that correct the image that falls on to the sensor by compensating for pitch (up/down) and yaw axis(vertical) movements, arriving at a better image result.

In camera stabilization works similar – but instead of a floating lens – it is the processor itself that is being moved.

While results are overall similar – the in the lens stabilization has a slight advantage, since the technology is adapted specifically for the lens.

While all of that sounds good and all – but does it help? Yes – it does! Always? Nope!

Here’s where IS helps. Handheld shots in low light. Everyone knows that shooting with shutter speeds beyond 1/125sec is, depending on the shooter, a risky business. IS can improve your odds in the range of 2 – 4 stops. (Come again?) Well – think of it that way. It’s dawing – and the available light fades away. You tricked out ISO to the max – opened aperture to the max – and still – your camera wants more light – the best you can get is let’s say 1/50sec shutter speed. The odds are – it’ll be shaky. Two stops will catapult it in practical terms to soemwhere of 1/100 sec, 4 to 1/200/sec, both actually managable – and hence you get a picture in good quality, where you couldn’t get one before.

Where it fails: Strong shake, fast movements, way to little light and believe it or not – on tripods. (at least it’s not recommended, it might produce odds results).

In general – compare it to cars ABS (Anti Brake lock systems). It’ll help in “normal” situations, but if you’re too fast – you will crash. In general it’s a support tool – not a miracle. Used accordingly it’ll help you considerably.

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Chromatic Aberration (CA)

Huh? Circumventing scientific explanations I will try an example. We all know that our white light contains

all colors in the spectrum. We have all seen, what happens when light is led through a prism. We see the whole rainbow spectrum. Now – in a lens light is led through optical elements and usually several of them.When we see chromatic abberations in our images, it means that the optical elements display this prism effect to a certain degree, because they haven’t been produced thoroughly enough to counter these effects.

And we end up – usually in areas with high contrast differences (e.g. dark and light) – with red, blue or purple fringes in between dark and light areas.

CA Effect left. Treated by desaturation – right

In general – this annoying effect does appear more frequently in cheap optics and more likely in a zoom lens than it does in a prime lens.

While there is nothing that can be done about it while shooting – some software like Adobe’s Lightroom and others can reduce it in postwork. From my experience so far I was not impressed however.
My method to get rid of it, is hands on and utilizes the fact that this effect appears in areas of hightened
contrast – and use the sponge tool (desaturation) tool of my software – most better software products
have it. I set a brush size of about the size of the CA’s width and set the desaturation value to maximum.
Then I zoom in as far as it makes sense and brush over the color abberations, until the color is entirely gone.

And – as you see in the above example – it works quite well.

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Focal Length:

While most everybody knows what’s behind that term – many however have problems put it in relation to real life. So here we go – I try to put focal length into perspective.

Before the time of Zoom lenses 50mm was the Alpha & Omega of all Lenses. Why? Because it is the closest resemblance to our human field of view. Not so much what the angle is concerned, but in terms of magnification. – It’s pretty much what we see. And ever since it has become a standard reference point.

With the advent of APS size sensors we have to add 35mm focal length as the equivalent to the 50mm lens in full frame cameras.

And from there we have a better way of determining, what a lens actually can do for us.

Important to keep in mind, what Camera sensor you use. Unless it’s a full frame camera, which currently are the exception, calculate with the 1.5X factor that has to be applied to the conventional focal length nfo.

A 10 -20 mm lens turns into a 15-30mm, 70-200mm into 105-300mm and so on.

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Macro:

When is a macro a macro? Well it ain’t a specific rule naming things, but in my book I call images macro, that show me details, that I can’t normally see – e.g. the hairs on a butterflies body.

Anything else is a closeup for me.

If I were to apply specific rules – I’d go with the magnification value, which already is a bit harder to grasp.

If you look at lens specifications, you often see something like:

Magnification: 1:2.

This value applies to how large the object appears on the sensor.

1:1: means a penny would appear on the sensor exactly in his original size.

1:2/1:3: means half or third of it’s original size

2:1: Twice the original size

And here three images to give you a better idea.

So looking at these examples I think it’s clear what I mean with my definition of when an image is a macro.

The first image is pretty much what I see with the naked eye. Image 2 already shows quite a bit of detail – like the wing texture etc. And the 3rd? I see Aliens! Here we have more detail than most people care for.

Anyway – pics 2 and 3 do qualify for the macro badge.

Next up in Part IV: A look at equipment

This entry was posted on Sunday, June 22nd, 2008 and is filed under Tips & Tuts. You can follow the comments to this entry through the RSS 2.0 feed. Comments are currently closed.