As with most "ultra wide" angle lenses of the olden days, this one has built-in filters. Can't say I am a big fan of this design, because you have to use one of the filters whether you like it or not. At least the design of the filter selection is one of the best I have seen. You push down on the ring and then turn to select the filter. The Takumar 17mm f4 fisheye, on the other hand, is terrible. The indentation is too light and the filter gets moved too easily.
The built-in filters are Yellow, Orange and 1A. In the end, it was interesting to experience with the yellow and orange filters in combination with the G1's black & white modes. The black and white pictures came out better than I expected with the filter dialed in, especially the yellow filter. The orange filter made the scene too dark. Now I know how the yellow and orange filters interact in black and white. Even though I shot in RAW, I could not process them as colour any more since they are just in shades of yellow or orange.
In terms of optical quality, I can't say how it performs in the edges, because the G1 uses a very small percentage of the lens. It's pretty sharp when properly focused. The contrast is in the low side. Pathetic in the flare resistance department. Side lights causes everything to have a white out effect. A hood is almost a requirement for this lens, but too bad I didn't have one on yesterday. The colour is on the warm side, since it's has a permanent skylight filter built-in.
The lens itself is solidly built, like most older lenses. Although the lens says mutli-coated, the front elements do not look multi-coated, perhaps that's why the flare is so bad, but the rear elements are multi-coated.
My take? It's a nice normal lens for the g1, although it's kind of slow at f2.8. Optically ok, but bulky for a 24mm lens.
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