Ray that very well may be the case. Mine was just purchased in October from B&H which presumably has a rapid turnover. Also, at the urging of a very knowledgeable friend, I bought some Olympus PC lenses to use on the Canon. Reportedly these are some of the best performing PC lenses out there. The Canons were better by a long shot so I resold the Olympus lenses. I don't know what to say. Mine Canons are good.
Of course, Kirk, you have never specified whether you are using a full frame sensor or a cropped format, as I recall.
Looking through the images from my latest trip, I see that stitched 24TS images with the camera positioned vertically, fare much better. With camera vertical, the stitched aspect ratio is almost square. Most of all four sides are well away from the image circle circumference. It's only the corners that are then rather blurred.
With camera vertical, the resulting stitch is virtually double the file size of a single shot. One might be led to the opinion that such an image (with the 5D) has the over all resolution of a 25MB digital MF back.
The following example looks rather detailed to me. Perhaps as detailed (or more detailed) than any single shot from the sharpest 35mm (format) wide angle lens that money can buy.
Here's a jpeg of the full 70MB (8 bit) image, downsized of course.
Here's a 100% crop of the centre (not downsized). It looks quite sharp to me, and of course this small crop is representative of a huge
The corners are quite blurred (believe me ) but that disappears quite rapidly as one moves towards the centre of the edges, which are reasonably sharp.
I don't think I'll chuck this lens away just yet .