realVivek wrote:
Seems to me that you are confusing field curvature with barrel/pincushion distortions. They are very different aberrations.
Absolutely not. Barrel and pincushion distortion are geometrical errors that are in the plane of focus, they make no difference to where the point of best focus is at different points in the image. It’s perfectly possible for the region of focus to be a true, two dimensional plane, (and thus for there to be no FC) and the image to be barrel or pincushion distorted in that plane.
Field curvature, on the other hand, is where the region of best focus is not a two dimensional plane, as in a flat field lens, but rather a curved three dimensional surface, some areas of which are further or back along the axial plane (it’s also possible for there to be distortion of course)
You can see from my post that you quoted that I talked about FC *towards* the camera. Towards and away from he camera are axial directions, in which the region of best focus varies with FC. Axial directions are irrelevant to distortion.
So I decided to try something that I’m not sure will work but I bought a PCX 5000 off the board. My one concern is it’s 50mm the 28 is 52. But it looks like I can just place the PCX in the front element without hitting and just hold it in place with a 52mm filter ring. Worth a try
I also grabbed a Hawks adapter from the board. That way I can adjust infinity
In that event, your best bet to check for changes in bokeh from field curvature (keeping all else the same) is the Minolta VFC 24/.2.8 lens.
DavidBM wrote:
Absolutely not. Barrel and pincushion distortion are geometrical errors that are in the plane of focus, they make no difference to where the point of best focus is at different points in the image. It’s perfectly possible for the region of focus to be a true, two dimensional plane, (and thus for there to be no FC) and the image to be barrel or pincushion distorted in that plane.
Field curvature, on the other hand, is where the region of best focus is not a two dimensional plane, as in a flat field lens, but rather a curved three dimensional surface, some areas of which are further or back along the axial plane (it’s also possible for there to be distortion of course)
You can see from my post that you quoted that I talked about FC *towards* the camera. Towards and away from he camera are axial directions, in which the region of best focus varies with FC. Axial directions are irrelevant to distortion....Show more →
That’s indeed a good choice being one of the few variable FC lenses made.
Of course it may not exactly keep everything else the same, as when it moves the elements to change the FC there’s no guarantee that nothing else changes.
I guess we know the bokeh change of infinity elements when centrally focussed at closer distance from *pure* field curvature- it’s just that things are less OOF in the periphery (for backwards FC).
Any other effect will due to the fact great FC is sometimes combined with other aberrations.
realVivek wrote:
In that event, your best bet to check for changes in bokeh from field curvature (keeping all else the same) is the Minolta VFC 24/.2.8 lens.
i ended up ordering from amazon for sony sensors. after ordering, i emailed them to make sure its optimzed for sony with order #. finally got noticed that it shipped today, took almost a week after ordering. dhl express and tracking shows it should be here by Friday. pretty fast coming from china =O lol. we'll see if it shows FE Plus on it.
Got the PCX 5000 today and placed it in a empty 52mm filter ring and than added a 52mm retaining ring juts like any other filter. I do see some improvement but once i get on Big Bronco i can tell better but even at F5.6 the corners look very good and improvement at F8
here at 5.6 . Im focused on the center speaker below TV
Again looks very good. I do think these are better than the images I shot before. I will test on Big Bronco and compare and also try flipping the filter around as well.
But I think I may have found my 28mm. One thing of note nice straight lines no bending and distortion at least here is looking very minimal. All good qualities for architecture work.
Sooo watch this . When using the PCX 5000 it is actually a tighter focal length than normal as you can see hear the little less space on the sides when using it. So now your a 29mm lets say
