Correct focus in panoramas

[Kit]

I have been shooting a few panoramas lately and have a problem. I read that you should use aperture priority, to prevent the camera from choosing mis-matched apertures, which makes perfect sense. I also read that you make a single point of focus at the hyperfocal distance, then turn focus off and shoot the images for the pano in this way, as the pp software will not be trying to match up differently focussed images when stitching. But this is what I get:



This is a crop from the pano image in the thread on the lake jetty and as you can see, there is a distinct line between two images, focussed and unfocussed, that made up the pano. The line between the stitched images runs more or less on a diagonal, from the bottom left to the top right, up the ridge and across the scree. There is a clear difference between the focus in this part of the pano. I sharpened fairly aggressively to accentuate this.

I am not sure whether I am mis-understanding the instructions, or whether the camera isn't behaving how it should, but I'd like some opinions on this. If you are making a pano, how do you handle the focussing?

[jiro]

In my opinion, based on the image, the issue is with the post-processing and not on the stitched pano shots itself. If this is an issue regarding focus the problem should be seen as horizontal anomalies but not vertical sharpness issues because clearly, your chosen aperture and focus points covered the foreground, mid-ground, and background focus well. My suggestion would be to use multiple layers in photoshop if you have one and then use masks to select the areas of sharp focus to combine.

Whe I tried to use photomerge function of photoshop to stitch multiple images for greater depth of field, the same result happened to me hence my suggestion to go manual on the stitching. Perhaps other members have a better software to recommend regarding this matter. Good luck on your study, Kit.

[Kit]

Thanks for the suggestion, Willie. I did use Photoshop's Photomerge, so maybe that is where the problem lies. I will have a closer look at the original files and see if there are sharpness anomalies there.

[Stevewebb]

I have tried a couple and failed dismally to be honest but I think that is because I am trying to use the stitch feature in the wrong situations.

However, I think you are right in locking the focus but shouldn't you be on full manual to keep both the aperture and shutter speed contant? Otherwise you might get different exposures accros the scene. Maybe on this one the shutter speed went too low and it is a camera shake issue rather than a focus issue.

[pjerry]

I always shoot in the M-mode. I make the decisions, not the camera.....
Could it be kit that the stitch used other parts of the picture. What I mean, is the picture in the centre (much) sharper than in the corners? Maybe the same as where Willie was referring to.

[nickjohnson]

Hello Kit,
I'd find it helpful to have some data about lens focal length, f stop, shutter speed.
Absent those things, here are a few things to consider.
Constant aperture and point of focus is a must.
Constant exposure is nice but may not be doable within the dynamic range of your camera.
Forget hyper focal – focus on the furthest thing you want sharp – often that is infinity so manual focus becomes easy.
Overlap shots by at least 30% . Also consider processing RAW files prior to stitching in a way that takes out lens field curvature and other aberrations. I use DXO – but Lightroom and PS camera raw also do this now.

HTH

p.s. also tell the old bloke in Northumberland when the ice / snow has gone when introducing new work.

[Kit]

OK, have had a look at the exif on the four files used for the pano.
In all cases, they were:
f/8, 1/160th, 80.00mm focal length, manual control.

I rely on using auto focus, as I literally cannot see clearly enough to focus manually. My hit rate using manual focus is about one in twenty. So my process in a case like this is to take an initial focus somewhere in the middle of the area I want in the pano and then to flick to manual focus to actually shoot the frames.

[Kit]

Oh.

This explains it, duh. I just went and had a look at the original sequence of images at 100% and there is one, the third to the right, that is....wait for it....out of focus. I must have had a bit of a sway or a wee trigger jerk or something.

That'll learn me to do my homework before asking the teacher a daft question!

[The Wirefox]

You can auto focus Kit but once the lens has found focus switch the lens to manual focus...or whatever you do with non-Canon models. Oh and dont for get to switch back...i did that and it confused the hell out of me for a while