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Spyder On... The Lens
The intro to lighting is full of theoretical stuff, so it’s time for a bit more ‘hands on’ practical stuff.
Every camera needs a lens, so this one (at least to start with) applies to everyone who wants to take a photo, not just we SLR and DSLR users.
Lens Diameter.
Photography is all trade-offs, and the lens you use will be no exception.
A tiny lens, like the ones you get on mobile phones or most compact cameras, will catch a lot less light than a large one.
Example (not that you need it yet)
I carry around 3 or 4 cameras most of the time ( sometimes I’m ashamed to say only 2, but I’m a father now and have other responsibilities).
One is a little compact that fits in my pocket and has a 6mm lens.
At the moment I have a 24-70mm zoom F2.8 sigma lens on my D2x, with a diameter of 82mm.
The sigma catches a lot more light than the compact lens, but they both meter the same when they’re on the same settings.
How come?
Well in this instance, think of light as information. The cameras meter the same cos they are both calibrated to the same standard, but the sigma will gather a lot more information (detail) than the compact.
So bigger is better then?
Eermm… no. (at least not for lenses)
If only. Although it’s true that generally big expensive lenses are better than small cheap ones, that has a lot more to do with the quality of the build than the lens diameter itself.
The major factors in lens quality are aberration and distortion.
Aberrations are when a lens doesn’t follow the curve it’s supposed to be. Unfortunately the larger your lens the harder it is to prevent aberrations AND the bigger the effect aberrations have on your final product. This is why big expensive lenses usually have loads of features to prevent this effect (and one of the major reasons they are so expensive).
Distortion is the ‘bending’ of the image a lens produces the further away from the centre of the image you get, and it is coursed by the curve of the lens itself.
The wider the maximum angle of lens you are using the greater the curve of the lens needs to be and so the greater the distortion. This is not always a bad thing, the extreme example of this is the fisheye lens, but any lens with a wider angle than 35mm has to distort the image to fit it into the frame.
This time it’s the smaller lenses that suffer. The smaller the diameter, the larger the proportional curvature of the lens and so the larger the proportion of the image which will be distorted.
Don’t panic if you’ve got a small lens in you compact camera, a lot of modern compacts actually use cut down versions of much larger lenses. All SLR lenses are set up to compensate for this distortion, but how well they manage this varies massively.
All in all, most of the time you’ll get what you pay for.
Looking after your lens.
Whatever type of camera and lens you use, you need to look after it, keep it clean and free of scratches.
Two simple ways to tackle this, but both worth looking at.
First off, always use a lens cap. If you are using an SLR and have a lens not attached to your camera make sure both ends are capped at all times. In addition to this get yourself a good UV filter to stick on to the front of your lens (an ever growing number of good quality compacts have either an automatically closing lens cap or have a lens you can attach a filter to). I have lost count of how many times a lens costing a good few hundred pounds or more has been saved at the cost of a filter costing only a few tens of pounds.
Quickie note: UV filters will not overly effect the appearance of your photographs as good UV filters will only reduce glare. Cheap UV filters can cause a colour shift, so be sure to get a good quality one. Personally I’d recommend Hoya’s Pro range, although their standard range is fine.
Secondly, now you are looking after your lens it may dismay you to see dust and fluff gathering on the lens or filter anyway. What to use to keep it clear?
Well a camera lens cleaning cloth is a good idea, but one for spectacles will do just as well. A lens cleaning brush with an air reservoir is also a good idea.
The most useful bit of kit I have for keeping my lens clear is my habit of wearing baggy soft cotton t-shirts, a quick wipe with the corner of the t-shirt and all is well.
Sorry to compact users, but it’s all SLR stuff from here.
Quickie note: I am amazed at how many people will happily spend a fortune on an SLR and then get cheap when it comes to the lenses. No matter how good you and your camera are, a photo can only be as good as the quality of the lens you use.
Using lenses, swapping lenses.
To get the best from your camera, you must know it and know it well.
Every time you change lenses on your SLR, you change your camera.
When you change lenses the weight and balance of your camera will change, so when you buy a new lens treat it as though you’ve brought a new camera.
I don’t just mean checking things like the speed and accuracy of the auto-focus (although that is important) I mean put the hours in to getting used to using your camera along with it’s new lens.
Example (and in fact the whole reason I started writing this article in the first place)
I’ve just got a new lens. The afore mentioned Sigma.
For the last year and a half I’ve used a Nikkor 24-120VR (F3.5-5.6) as my everyday lens and used fixed lenses for anything below that F-number minimum.
This can be a pain as it means carting around a number of lenses or more often, forgetting to pack the one I actually need.
So I finally got round to checking the lenses available and found a very reasonable priced lens with a constant minimum F-number. Not as low as my fixed lenses (F1.4 most of them) but at F2.8 it’s low enough for most uses.
I picked it up yesterday, so happy-clappy me I have a new toy!
But this is where I have to tread carefully, or I’m gonna suffer later.
My Nikkor has the zoom ring at the front of the lens, with a clockwise twist to zoom in and the focus ring directly behind it. By now my left hand always holds the lens by the zoom ring and never touches the focus ring and I can zoom to any part of the lenses range without looking at the camera or through the view finder at all.
This Sigma however not only weighs half again as much as the Nikkor but also zooms anti-clockwise with a zoom ring behind the focus ring. The focus ring is now just where my hand tends to hold the lens. I can’t tell you how many times that’s tripped me up in the last 12 hours. This change-over is gonna trip me up just when I’m not thinking about it, which will be when I’m concentrating on an important or tricky shot. My only answer, for the next week or so I’ll be using my new lens as much as possible, with odd switches back to the Nikkor to trip up my subconscious.
This (as ever) is all a bit extreme for Joe Average. My recommendation (and something I do myself anyway) is that if you are going to use more than one lens in a shoot, fit each lens in turn to your camera before you start, make sure it’s working, do a few test snaps. This will tuck the fresh memory of the cameras feel with each lens in your head and make it so much easier swapping lenses later.
Dust to dust.
All this lens swapping does open your DSLR to a new risk, one that no compact or film SLR suffers from. Dust on your cameras CCD.
The worst thing about dust on the CCD is those times it happens but doesn’t show up on the cameras display, only after the shoot is over and you’ve downloaded the photos do you realise you’ve got either hours of work cleaning up the photos or it’s delete the lot and start again.
If you ever change lenses on your DSLR then you WILL one day get dust on the CCD, so lets not bother about the ways of keeping it out.
As for the cleaning, each camera is different, the most important point to make in this section is find out what the manufacture recommends, you risk destroying your camera if you clean the CCD incorrectly.
The only general advice I’ll give is to get yourself an air canister, one specifically made for cleaning as others may contain propellant that can damage the camera.
9 times out of 10 this will clear your camera without any more fuss.
If all else fails, take you camera to a professional cleaner.
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