How to stitch photo the hard way?

In article <h9ao4i$eu8$ says…

I have a photo larger than my scanner so I had to scan it as two separate section with some overlapping.

The two sections are about 4000 x 3000 each.

Now I want to stitch them together. What I do is load each section into a layer in photoshop and do a rough alignment. Now in order to align them perfectly, I zoom in to pixel level at one side of the overlapped area, make one layer 50% transparent and nudge until the pixels line up.
Then I zoom in to the other side of the overlapped area. Often, I need to rotate one of the layer to line up everything. Ideally I would put the center of rotation on the previously lined up area, and then drag the rotation handle to line up the current side. But at the pixel level, the rotation handle is not visible. If I zoom out until I can see the rotation handle, I can no longer see enough detail to line up the two layers with pixel accuracy.

How do you get around this problem?

I know there are stitching function in newer photoshop and standalone stitching software. But just for the challenge, how can I do this the way I want?

The following works for me on PS7.0 (which doesn’t have fancy alignment software) and assumes the two image halves overlap a little, and that they are within a few degrees of rotational alignment.

1) Place them as two layers and align them approximately horizontally and vertically by eye (without rotating!!!).

2) Now zoom in (to pixel view) to one side of the image (I am assuming the images are upper and lower halves) at a point where the overlap occurs and, assuming you have sufficient pixel contrast to do so, nudge until you have the pixels as close to spot on at that side. You can use transparency or whatever to help here.

3) Now zoom out and select one of the layers and hit Transform Rotate. Before doing any rotation, drag the rotation centre point locator to the approximate point where the pixels have been overlapped correctly (it is the circle with the cross and dot in the centre – looks a bit like a telescopic gun-sight). Zoom in using Ctrl + and the side sliders to position the rotation point accurately on the exact point where you achieved the pixel match.

4) Now use Ctrl – and the sliders and Ctrl + to get to the opposite side of the image (at pixel view) where there is a visable ‘wedge’ where the pixels don’t match due to rotational inaccuracy. You can enter an angle into the ‘Control bar’ at the top (the one that becomes visible when you enter Transform – Rotate) – it is the box next to the little triangle 5th from the left or 3rd from the right. Start by making 1-2 degree adjustments, and then by triual and error get down to tenth of a degree (or less) till you have a good pixel match on this side.

5) Ctrl – out and check that you matched the pixels and not something else – then accept the change. Bring the layers up to full opacity and if you have sufficient overlap fade a mask in on the bottom edge of the top layer. Merge layers etc, and you are done.

As long as the images are top the same scale, you should be able to get near perfect match by tis technique. If they are out of scale, you can add a scaling step the same way, although the pixels get a bit muddy and it is a little more trial and error.

Mike

"david" wrote in news:h9ao4i$eu8$:

I have a photo larger than my scanner so I had to scan it as two separate section with some overlapping.

The two sections are about 4000 x 3000 each.

Now I want to stitch them together. What I do is load each section into a layer in photoshop and do a rough alignment. Now in order to align them perfectly, I zoom in to pixel level at one side of the overlapped area, make one layer 50% transparent and nudge until the pixels line up.

Then I zoom in to the other side of the overlapped area. Often, I need to rotate one of the layer to line up everything. Ideally I would put the center of rotation on the previously lined up area, and then drag the rotation handle to line up the current side. But at the pixel level, the rotation handle is not visible. If I zoom out until I can see the rotation handle, I can no longer see enough detail to line up the two layers with pixel accuracy.

How do you get around this problem?

I know there are stitching function in newer photoshop and standalone stitching software. But just for the challenge, how can I do this the way I want?

Try using the "DIFFERENCE" screen mode (drop down in layers palete) I find this invaluable when trying to line up pixel perfect joins

see Matching Oversized Scans
http://www.design-u.org/Photoshop/monroy/matching.html

Kingdom wrote:

"david" wrote in news:h9ao4i$eu8$:

I have a photo larger than my scanner so I had to scan it as two separate section with some overlapping.

The two sections are about 4000 x 3000 each.

Now I want to stitch them together. What I do is load each section into a layer in photoshop and do a rough alignment. Now in order to align them perfectly, I zoom in to pixel level at one side of the overlapped area, make one layer 50% transparent and nudge until the pixels line up.

Then I zoom in to the other side of the overlapped area. Often, I need to rotate one of the layer to line up everything. Ideally I would put the center of rotation on the previously lined up area, and then drag the rotation handle to line up the current side. But at the pixel level, the rotation handle is not visible. If I zoom out until I can see the rotation handle, I can no longer see enough detail to line up the two layers with pixel accuracy.

How do you get around this problem?

I know there are stitching function in newer photoshop and standalone stitching software. But just for the challenge, how can I do this the way I want?

Try using the "DIFFERENCE" screen mode (drop down in layers palete) I find this invaluable when trying to line up pixel perfect joins

That seems to be one of the easier way, and the OP wants to HARD WAY. My guess would be doing it with the eyes CLOSED. Or hands behind ones back?