Lens Adapter
The LA-DC52 lens adapter fits on the body of the camera (not the lens) and extends just past the camera's extended lens, providing a 52mm thread. This allows the attachment of filters, and step up/down rings to more filters, filter systems such as Cokin, lens hoods, and the rather more expensive wide/tele/macro lensesNote that the lens adapter obstructs the flash and so casts a shadow bottom right, so flash is not recommended. Ditto for view-finder, so use the LCD to compose.
Any standard filters can be used on the A40. The lens adapter gives a 52mm thread, but if the filters are a different size, then step rings can be used to increase or decrease the thread. The only thing to watch out for is that if the filters are too small, there may be vignetting, which is where the filter blocks the corners of the photo.
With a step-down ring to 49mm, one can usually avoid vignetting by zooming slightly - though of course it's better to step up rather than down and so avoid that problem completely.
The LCD is a bit like the viewfinder on an SLR camera, so you will directly see the effect of adding lenses and filters.
The built-in camera lens cannot be replaced the way that SLR lenses are, so regular SLR lenses cannot be used. Only lenses which can be added on, to convert an existing lens, will work.
Canon lenses are expensive, but they are made to work with the camera, so they should give a good result.
Non-Canon lenses can also be used, but the only way to be sure if they give a good result is to try them.
I picked up my lenses on eBay for about 10 UKP each - at that price I was willing to risk that they might not work, though I was very careful to check that they were made by reputable manufacturers.
(Even though my Wide lens is by Canon, it is a larger size than the one for the A40, so I wasn't sure it would work before I bought it.)
Lenses
I don't really know enough about camera converter lenses (wide, tele,
etc) to know if some lenses might be more compatible than others ... so
I'd hesitate to suggest anyone spend a lot
of money on a non-proprietory lens without first being sure that it'll
work. In the UK, the Canon wide and tele converters are about 60 - 70 UKP, and the 250D close up lens is about 50 UKP.
Of course, or should I say hopefully, one would get a better image quality with the more expensive lenses - but perhaps above a certain level probably only a professional photographer could tell the difference.
I wanted to be able to try such things, and I would have liked to have bought Canon, but the prices were prohibitive, so I had a look on eBay. The idea was that if anything didn't work out I could always sell it again. And after all, I didn't know how useful these lenses would really be to me, so it wouldn't be worth spending too much on something I might not use much.
I always looked up the manufacturer on the web so I didn't end up buying some cheap plastic lens. I also checked the sellers' ratings, and looked for some indication of the condition of the lens - i.e. unmarked and without fungus. Also that they weren't going to charge too much for post & packing.
Close-up Lens
The Canon 250D close-up lens has a focal length of 250mm, and which is therefore only +4 diopters.
focal length(in meters) = 1/diopters
Canon also do a 58mm-thread 500D lens, which sounds better but which is in fact 500mm, and thus only +2 diopters.
(Ordinary close-up filters come in +1, +2, +3, +4 and +10, and can also be combined to give greater magnification.)
But the Canon lens would hopefully be good quality, and might be a little sharper at the edges ... I've not tried it.
I have a 49mm Dia Zoom Close up Lens, which is variable from 45cm to 5cm -
though I haven't used it much, and I haven't yet worked out what exactly
that means in terms of magnification. Vignetting is only a problem with
the camera at wide angle, but I normally have the camera zoomed for
close-ups.Wide Converter Lens
I have a Canon 55mm 0.7x Wide Converter which seems to work fine
with a step-up ring. (Important not to step down for a wide lens because
of vignetting.) However, it shows some significant chromatic abberation
towards the edges.Tele Converter Lens
I also have a
Tokina 2.0x Video Tele Converter, which though only 49mm came with its
own step down ring. Vignetting is only a problem with the camera set at
wide angle, but the tele lens is most likely to be used with the camera
zoomed. This also shows some chromatic abberation towards the edges.
Filters
Basically, the
filters of most use with digital cameras are those that actually change
the content, rather than filters that simply adjust the visible
spectrum, because the latter can usually be
adjusted in post-processing. So, with the exception of Infrared filters and Neutral Density or Grad Grey filters, all the light balancing/colour correction filters are probably unnecessary, including those described as "black and white", half-color, grad-color and "color spot" filters.
Useful Filters
A polariser (circular unless otherwise specified) will cut
reflections, and accentuate sky and cloud. A Neutral Density filter will allow longer exposures in bright conditions - running water, etc.
Graduated Neutral Density will even up exposures for high contrast background and foreground. (Cokin style grad filters more versatile here, but they're perhaps not the quality of glass.)
Perhaps a UV/Haze/Skylight, not so much to cut UV which many digital cameras do anyway, but to "protect the lens" from dirt & scratches - though I've heard this is the sign of an amateur ... every extra layer of glass degrades the image to some extent ... better to cushion the lens with a lens hood ...
Close-up (dipoter) filters, which are really lenses ... can be stacked together to give greater magnification ... significantly cheaper than a proprietory macro lens, but perhaps a little softer at the edges
Filters such as diffusers, fog and soft spot are probably of less use.
And then there's the toys ... star or cross and spectral filters, rainbow and multivision filters, split-field and center-spot, etc ... might be fun to play with if one can pick them up cheap second-hand ...
If buying on eBay, look for branded filters (Hoya, B+W, etc) plus some assurance of condition ... and check postage costs and sellers' feedback ratings.
There's an excellent article on filters for digital cameras at
http://www.cliffshade.com/dpfwiw/filters.htm
Close-up Filters
These are really lenses, but they look and fit just like filters, and cost not much more. They are certainly cheaper than the Canon close-up lens, and can be stacked together to give greater magnification. Most of my macro photos are taken using filters like this.
Close-up filters are measured in dipoters, and normally come in +1, +2, +3, +4 and +10 diopters. The dipoters indicate the refractive capacity of the lens.
Magnification and diopters are related, in that
magnification = dipoters/4 + 1
So a +2 diopter filter will give a magnification of 1.5
But it's not used in the same way as, for example, a 1.5x tele lens, where you add the lens and, from the same position, everything becomes 1.5x bigger. Instead, a close-up filter or lens lets you focus at a much closer distance.
The filters can also be stacked together, so putting together a +3 and a +4 will give +7, which is equivalent to a magnification of 7/4 + 1, which is 2.75x (... however, it's best to stack as few as possible, because every glass/air interface will degrade the image a little).
It is also recommended when stacking close-up filters that the higher power filters are placed closer to the camera lens.
Note however, that with close-up lenses/filters the depth of field also becomes shallower, and so the autofocus range becomes more limited. The greater the magnification, the more focusing is about moving the camera to get the subject within the camera's narrowing autofocus range. But then the LCD gives a good indication of when the subject comes into range.
In the macro shots I've taken, switching to the narrow aperture can make a significant difference by adding just a few additional mm of DOF.Notes:
- A nice little article which explains the relationship between diopters, magnification, and focal length can be found at http://www.lightspc.com/magnification_principles.html
- I believe, if you're handy enough to assemble an attachment of
some sort, even a cheap magnifying glass (say 5x magnification) can give
impressive results - though DOF will probably be just a few mm.
- I took a couple of close-up photos of some dried lavender, the
only difference between them being the 'wide' one was at f/4.8 and 1/15
sec, and the 'narrow' one was at f/14 and 1/2 sec.
In the large sized versions, switching from one to the other and comparing foreground and background, one can certainly see the difference in DOF.
Polarisers
These cut down reflections, so reflective surfaces (glass, water, etc) become transparent. Also intensifies blue skies, and by cutting down on the reflections the polarizer seems to really bring out the colours of other objects.
The effect of a polariser is greatest at right angles to the sun, and, as one moves round, the filter needs to be rotated to maintain the best possible effect.
Pointing directly towards or away from the sun will have virtually no effect, the polariser acting simply as a neutral density filter.
With wide angle photos, the diminishing or increasing effect may be seen across the sky as a graduated blue.
If using a polariser with other filters, put the polariser on last, to avoid stripes or wavy lines.
Circular (PL-CIR) or Linear (PL)?
If a camera uses a beam splitting mirror with sensors behind it, for autofocus or metering, then a Circular Polariser is required for the beam splitter to work properly. Most autofocus SLR cameras are like this.
However, most autofocus digital cameras don't use beam splitters, so a linear polariser will normally suffice. But if in doubt, get a circular one.
The A40 should work fine with a linear polariser.
.
Grey or Neutral Density Filters
A Neutral Density (ND) filter reduces the amount of light that can pass through the lens, so it can be used to
- reduce the intensity of the light - where even the smallest aperture and fastest shutter speed is not sufficient.
- allow a slower shutter speed - to blur movement, such as in waterfalls.
- allow a larger aperture - to create a shallower depth of field
Different manufacturers indicate the stops of the lenses in different ways: where Tiffen & B+W filters show 0.3, 0.6, and 0.9, Hoya shows 2x, 4x, and 8x, to indicate 1, 2 and 3 stops.
A Polarising Filter will also act as an ND filter, adding about 1.5 to 2 stops to the camera.
Graduated Grey or Neutral Density filters
These can be used to even up exposures when there is a big difference in brightness between top and bottom halves of the composition - e.g. bright sky and dark foreground.
Circular screw-in type filters will need the horizon to be placed on the point of transition of the filter, which is often the middle, so it might be wise to allow for some cropping of the photo to give a better balanced composition. On the other hand, 'Cokin-style' square filters can be adjusted in the holder to fit the horizon in the composition, but the quality of such filters is often less than that of coated glass filters, and the grey of Cokin filters themselves is not quite neutral.
A polariser might also be used in conjunction with a graduated ND filter, to accentuate the colours.
The effect of a graduated filter can be simulated on longer exposures by obscuring part of the lens with a thick card for part of the exposure. This can be a little tricky with small lenses, but is quite possible with some practice.
Note:
With post-processing, it's true that quite a bit of detail can usually be brought out of under-exposed areas - though even darker areas need contrast, and adjusting curves never quite seems to do it-, but I've found that the detail in blown highlights is just not there. If I have a light sky and dark foreground, and meter on the sky, then some post-processing can be done to recover the under-exposed foreground, but if I meter on the foreground, then the detail in the sky is totally lost.
Another alternative is to take two shots of different exposures, and then combine them, which will usually require a tripod and a non-moving subject.
IR Filters
See http://www.wrotniak.net/photo/infrared/
I've tried the TV remote test on my A40 and it works fine. And there's an optional lens adapter for the A40 to allow the use of converter lenses and filters. There's also a maximum shutter of 15sec, so the long exposures shouldn't be a problem either.
Unfortunately I don't have an IR filter, so I haven't been able to try it out ... the most I've managed is a 25A filter on a sunny day and, as you can imagine, the results were not exactly impressive.