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06-23-2012, 01:59 AM   #1
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Lens for K-x advice...

Hi all,

I bought a Pentax K-x that came with the Sigma 18-200mm Zoom lens that I'm very happy with.

After a year with the camera, I'd bought from Ebay a couple of accessories, so I could start to explore other uses... I purchased a:

- UV Filter 52mm
- Macro lens 52mm

The only problem is (and this is entirely my fault) I automatically thought that they would simply fit the current lens that came with the camera, but they don't! The lens is far wider and I was wondering if anyone could offer any advice on what to do. Are there adapters I can use? Is the lens I have not suited adapters therefore would I need to buy another basic 52mm lens kit? Any suggestions greatly appreciated.


06-23-2012, 02:30 AM   #2
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Hi Vanessa,

Regarding the UV filter, each lens has a filter diameter marked on it 49, 52, 55 and 62mm are the diameters of my lenses so ideally you need filters of the same diameter.

Second - the Macro.. REALLY not a good idea to use 'add-on' lenses as they effect the quality of your images adversely (and/or reduce the aperture range of the lens - and it's already a pretty slow lens).

SLR's are designed to take extra lenses, rather than add-on lenses. For Macro stuff your current lens may well do ok as it'll focus fairly closely, but if that's not enough then there are a LOT of better options.
06-23-2012, 03:08 AM   #3
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Filters/Focal Length?

Hello Vanessa. Welcome!
Katier is right; the 18-200mm size is the FOCAL LENGTH (in the case of your zoom, it's actually a focal range). In other words, at the 18mm setting it's a wide-angle lens and at the 200mm setting, it's a telephoto. Another name for zooms is Variable Focal Length.
The filter SIZE is a whole different kettle of fish; The front of any lens is a certain diameter, which doesn't change when you zoom. If it's 62mm, it will always take a 62mm filter. Along the front rim (somewhere) it will have the filter size. Also the lens hood (if included) and lens cap will have a size printed on it somewhere. That's the filter size. All should be the same.
Generally, you can go UP (larger) in filter size with an adapter; Using a smaller filter (smaller than the front element or normal filter size) is not recommended. It cuts off the light and usually adds a shadow or black "frame" around the edges of the picture. This is called "Vignetting" and looks terrible.
So, if you want a UV or Skylight filter for your lens, find the size printed on the lens and get one in that size.
I'd hang onto the 52mm UV; It's a common size and you might get a lens in the future that uses 52mm.
If you want to try macro, the best investment is in a true macro lens, generally they'll run around $100-$150 USD for an older manual-focus prime, 50mm or 100mm, the most common macro sizes (I'd avoid "macro" zooms JMO) and $200-$300 for a (used) auto-focus macro prime. A new macro auto-focus will be $400-$500.
A "Prime" is a lens with a fixed focal length, like 28mm, 50mm, 100mm, etc.
A zoom, as you know, has a variable focal length. Generally, primes are sharper, smaller, faster and lighter. Zooms are more versatile
Good Luck!
06-23-2012, 03:12 AM   #4
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Also, although some lenses are labeled "macro," they are not true 1:1. You still might be quite happy with some of those.
Best wishes.

06-23-2012, 07:06 AM   #5
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Unfortunately there is no way to adapt those accessories to work on the Sigma. You could resell them on the forum Marketplace, or hold them for future use, since 52 mm is a common front filter size, if they didn't cost you a lot of dough.

You will find many forum members who are proponents of front-mounting macro adapters. So I would not necessarily be discouraged from using one for macro photography. The Raynox DCR-150 seems to get some great reviews here among the macro enthusiasts.

A dedicated macro lens would produce better image quality than an adapter, but at generally higher cost and weight. And depending on how one defines it, "better image quality" is not always what you want when doing macro photography.
06-23-2012, 07:25 AM   #6
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You can get 'step-up or step-down adapters (basically just metal rings) that could get your current UV/Macro filters to fit your 18-200. However 52mm (your filters) to 62mm (your lens diameter) is a very uncommon fitting and could also introduce vignetting (darkening of the corners) into your shots from the adapters. Best bet is to sell off your filters (they can fit any lens of 52mm - so not just Pentax but Nikon/Canon etc. so you shouldn't have a problem selling them) and buy the right size filters (62mm) which will be a little more expensive because of the size.

IMHO the UV filters won't have any visible benefit (unless you are using your camera on a beach or for motocross/rallying or other sports where dirt and grit can get thrown at you and your lens) and if not a premium brand will probably detract from the lens IQ. The macro filter is just a fun filter and not for serious use. I'd not bother to replace either if it were me (we live and learn) !

For macro the Raynox 150 & 250 (as mentioned above) are just superb and incredibly good value. A massive improvement on the usual macro filters and they cost very little. I use them both (150 is better for flowers etc. and 250 for insects as you have to get closer).

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