Originally posted by Aaron28 thanks...will check it out
seems I will hafta to learn its sorcerous ways!!
Aaron, read this useful thread, particularly the section about field curvature which the DA15 has a good amount of.
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This is why, for example, DXO close-up charts and close-up brick wall images show the field curvature of the DA15. Field curvature is lesser the more you stop the lens down and the DA15 also has less field curvature when focused further towards infinity. In close up flat surfaces the edges of , for example, a brick wall can be out of the depth of field meaning the centre is sharp where you placed focus and the ends of the wall are further away and out of acceptable depth of field. A concave curved brick wall would result in a sharper edge to edge photograph.
The corners and edges can also easily be out of the depth of field when using such UWA lenses such as the DA15, for example, objects a few feet away, the ground, a nearby wall being out of focus and distant mountains being in focus. Again stopping down the lens gives you greater depth of field.
In wide landscapes typically focusing about 1/3 the depth into the frame will usually give you acceptable depth of field of distant and close objects. Using f4 or f5.6 won't achieve this and I typically use f11 - f13 on the DA15 which also happens to create the most defined star or sun bursts.
I still find the DA15 very sharp at f11 or so from years of using it and 1000s of landscape photographs.
The above is why you have to learn the DA15
I have the HD DA 20-40 Limited and you don't have any where near the field curvature effect of the DA15 which is why I love using it at 20mm where the DA15 can throw up field curvature problems.