Flat prime WA lens question

I'm doing a photo mosaic of a shallow water wreck for a project. My Tokina 10-17 still has too much distortion at 17 for Photoshop to assemble a mosaic. I'm thinking of going to a prime 24, 28, or 35. (also thinking of using it as a shark lens) Any thoughts as to what will give me an image with the least distortion?

The 24mm range is great for sharks.

Cheers

James

I'm doing a photo mosaic of a shallow water wreck for a project. My Tokina 10-17 still has too much distortion at 17 for Photoshop to assemble a mosaic. I'm thinking of going to a prime 24, 28, or 35. (also thinking of using it as a shark lens) Any thoughts as to what will give me an image with the least distortion?

Interesting, have you any published mosaic examples on the web? You can try converting the images with fisheye projection to rectilinear projection using for example the PTlens program.

However, you will still have the perspective distortion, depending on subject distance, field of view(focal leangth) and if the subject has 3D features. This will give paralax error in the mosaic picture. The situation can be improved with; longer subject distance, longer focal length, more overlap(smaler fov) and by aligning the photographs so that protruding features are in the centre of images. However, you have consider viz in all this.

Cheers

I'd recommend using Hugin:

http://hugin.sourceforge.net/

You can download the lens database (which has parameters for the Tokina 10-17mm at 17mm) from here, then load those settings to correct for distortion:

https://sourceforge.net/project/showfiles.p...ckage_id=187932

If you want to calibrate at a different focal length you can follow this tutorial:

http://hugin.sourceforge.net/tutorials/calibration/en.shtml

EDIT: You'll probably have to calibrate it for underwater use as a dome port will change the FOV etc, so you'll need to take a shot of a few straight lines underwater then follow that tutorial. Also worth trying uncalibrated with the fisheye option to see how that works.

Thanks for all the tips guys. I have an 18-70 that seems to have fairly straight lines at around 24mm - 28mm so I may try that. For my purposes, I wonder what would happen if I tried it behind a flat port instead of my 8 inch dome I was planning on using. I also may try making three passes over the wreck rather than two while taking more images. After my first attempt, I also found out how important it is to make sure the camera is level. That's critical for straight lines.

Hugin looks interesting. I downloaded it and will give it a try. Thanks!