06-25-2012, 12:34 PM
[quote name='wim' timestamp='1340462875' post='19044']
Actually, the real reason for less effect on a WA lens is that we are resolution limited by the sensor in cases like this. The larger AoV makes that the sensor has much fewer pixels available for a given subect, and distortion of that subject, than with a longer lens, and aberrations will therefore be less visible. OTOH, a WA lens has more DoF, so the whole pane surface may get into DoF, where with a long lens this may not be visible.
[/quote]
Well, these points are all interrelated of course. Yes, with a wide-angle you have more DOF, so in the ultimate case, the window pane is within DOF, so any imperfections show within the glass- still rays from behind will be misdirected, but they will be limited to the area of imperfection - I guess the most obvious cases are macro images of dew drops, where something in the background is now in focus. If you "zoom" in to an area of imperfection with tele, obviously now much more of the image is affected. That's basically what I tried to say with the dioptre case.
Yes, this was really old style window glass, you could see imperfections by eye (not modern day glass, which is pretty good).
I suspect as much. Still, it would be nice to see really well controlled tests. Some say also it could be a focus shift caused by the filter.
Anyway, here is a somewhat reasonable test on a 100-400, where a Giotto's UV filter doesn't work so well, while two others are fine:
http://forums.dpreview.com/forums/readfl...535&page=2
Actually, the real reason for less effect on a WA lens is that we are resolution limited by the sensor in cases like this. The larger AoV makes that the sensor has much fewer pixels available for a given subect, and distortion of that subject, than with a longer lens, and aberrations will therefore be less visible. OTOH, a WA lens has more DoF, so the whole pane surface may get into DoF, where with a long lens this may not be visible.
[/quote]
Well, these points are all interrelated of course. Yes, with a wide-angle you have more DOF, so in the ultimate case, the window pane is within DOF, so any imperfections show within the glass- still rays from behind will be misdirected, but they will be limited to the area of imperfection - I guess the most obvious cases are macro images of dew drops, where something in the background is now in focus. If you "zoom" in to an area of imperfection with tele, obviously now much more of the image is affected. That's basically what I tried to say with the dioptre case.
Quote:Having said that, even the worst filter I have ever come across is a lot better than the window pane you descrbe. I have shot with the 100-400L through double window panes, with good results. I lost a little contrast, but that was easily fixed in postprocessing.
Yes, this was really old style window glass, you could see imperfections by eye (not modern day glass, which is pretty good).
Quote:Personally, I can't complain about the bokeh.
Do note that if one takes shots of objects with thin, elongated and/or angular objects in the background, like grass stalks or grain stalks, yes, the bokeh can get a little busy, and not necessarily pleasing. However, very few lenses are capable of handling that well in the first place, although the 100-400L does remarkably well at that (as both these pictures show).
In short, IMO, to parpahrase Mark Twain, the rumours of the effects of filters on bokeh have been greatly exaggerated.
Kind regards, Wim
I suspect as much. Still, it would be nice to see really well controlled tests. Some say also it could be a focus shift caused by the filter.
Anyway, here is a somewhat reasonable test on a 100-400, where a Giotto's UV filter doesn't work so well, while two others are fine:
http://forums.dpreview.com/forums/readfl...535&page=2