----- Original Message ----- From: "Mark Cassino" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Wednesday, September 17, 2003 1:17 PM Subject: Re: First Pano Try
> I was shooting between 20 and 24 with the FA 20-35 zoom. There was lots of > distortion of near objects, not much distortion of distant objects. One of > the seams fell into just empty water, so the distortion there is not > apparent at all. Another fell on the rocks and the distortion was very > apparent there - the same rock looked very different in the different > frames. There I just picked which image to use and dealt with it when > blending the two exposures. this is why you use panorama software. it reprojects each frame of the flat film onto the surface of a cylinder accounting for the lens focal length. this is the preparation needed so that the images can be more or less overlaid. any mismatches should be purely because of scanning and camera movement. this assumes no distortion in the lens aside from the projection of a portion of a cylinder onto the film's flat plane. this is never true. scanning also has slight movements too and that adds some alignment issues. > That does make sense now that I think about it - but I shot horizontally. shooting portrait is to get as much up/down as possible. otherwise when put together, it can look very squashed in perspective. > I scanned the right side of the finder till I found a distinctive object, > then just unlocked the base of the ball head and moved it till it was on > the left side of the frame. The overlap was not much - maybe 10 - 20%. that is as much as you want to go when assembling by hand. too much blending otherwise. using a program to do the blending means you not only should overlap more but the results will be better with a good program. > No, not at all. Never even thought about it. > > BTW - what is the 'true center?' of a lens? =:-0 this is the nodal point. a camera rotated about the nodal point will not show a left/right movement of nearby objects since the camera "moves" left or right during rotation. > I _was_ fussy about leveling - I put a level into the camera hotshoe and > worked my way up from the small circular level on the tripod, to the two > horizontal levels the tripod head, to the level on the camera itself. I > also checked that as I rotated the camera, the horizon did not shift up or > down in the frame. Probably because of lens distortions, I had to shoot > with the film plane straight up and down - even with the tripod fairly > close to the water (I was 10 to 15 feet out in the river) the horizon > tended to be more vertically centered than I wanted. leveling is important only when you need a level horizon. if you deliberately are excluding horizon you may not care. looking down over a cliff is a case where you don't need/want it level. > Photoshop was it - I created a large blank image big enough to hold all > three exposures, and then just added each one as a layer on top of the one > before, making the new layer temporarily transparent to be able to line it > up. Then I dropped the new layer onto the old and use the eraser tool at > varying levels of transparency to blend the two. After that I cleaned up > with the clone stamp and used the dodge and burn tools to correct for > obvious differences in how the water reflected back light in the different > frames. Photoshop Elements 2.0 has this as a builtin function. it is one of few places where Elements has something that isn't at all in full Photoshop. it takes me about 10 minutes on average to stitch a 4 -6 photo panorama using specific software. the time savings is a lot. Herb....
