What's causing this?

Help...!

This is a 100% crop of a hdr image, what is causing the colour fringing? It is also on all 5 RAW files, although not as bad as here.

It was taken on a K20D - DA*16-50mm lens, set at ISO 100 - 26mm - f11 - 1/5sec.

[IMG]http://i336.photobucket.com/albums/n327/ali_graham13/forth-bridge-1.jpg[/IMG]


Here is the whole image.

[IMG]http://i336.photobucket.com/albums/n327/ali_graham13/test.jpg[/IMG]

i have seen this on some of my other shots. Also notice this on my DA*50-135mm.

This is not happening all the time, just annoying when I see it!

So is this lens or body? I presume it's a lens problem, but not both the DA*'s?

Anyone else had similar problems?

Thanks in advance.

First guess. If it's HDR then is it simply down to camera shake/movement between the shots?

look at your raw files... any aberations or fringing there? if so it will be amplified in hdr.
your best bet may be to process your files in silkypix and correct for the aberations then export them as tiffs or dng's then do your hdr processing....
oops re read, yes if it is in the raw files you have to correct it first in each file then process the hdr.

1/5th sec is very slow, was the camera on a tripod? If it was, did you turn off Shake Reduction?

The bridge shows what looks like camera shake but if this is the result of HDR software, it hasn't aligned the images properly.

The green and magenta edges are classic chromatic aberration (CA). Did you have a filter on the front of the lens? If so, take it off. The DA* 16-50mm lens should not produce that much CA unless there is a problem with it.

If the problem is CA then you can sort that out with most photo programs which have some lens correction.

A small side issue, What have they done to the Bridge? What are the white things zigg zagging up and down truss 1 and 2? I have a soft spot for The Forth Bridge 20 or so years ago I was involved in a firework gig on it. The sponsor was Scottish Power and we spent many day s climbing on this amazing structure installing pyro to spell the name off the sponsor in letters 10meters high. great fun... Jeff

Thanks for the replies...

Gareth, I had this on my Manfrotto tripod, with 2 second delay, mirror up.

Don, yes they are on ALL my RAW's.

Peter, I had it on a tripod, 2 sec delay, mirror up, Shake reduction was on but, I think, is cancelled when 2 sec delay used. I had my UV filter on front. Have seen the debate on this, may try some without to see if there is a difference. I'm just not sure if it's the lens or filter. Could it be the body? I know it sounds stupid but...

Stefan, yes managed to get rid of CA on re-visit to RAW converter.

Finally Jeff, The white covers are because of painting going on at the moment. It could be the last time its is painted as they are putting on some sort of new 'paint'. It is supposed to last much much longer...

Thanks again...

It isnt camera movement or the SR, it's CA because you could remove it that way.
The CA is caused by the optics so the filter glass and the micro senor all probably at something.

the biggest problem might be the filter, the lens is designed for the light to hit a lens a certain way and the correction in the lens is made for that but a filter might change the light before it goes through the lens.

This might explain things http://toothwalker.org/optics/chromatic.html

I think the CA that you show may be due to the filter. Retake the shot without it.

I think also that your HDR software is not behaving properly. If you look at the spans of the bridge in the last shot you posted, there appears to be multiple images superimposed.

How many images did you use for the HDR?
Which software did you use?
Did you change focus point or move the tripod between shots?

Try this:- Take the image that was correctly exposed and make JPG's from that one image that differ by 1 stop from each other (-4 to +4 exposure compensation, 9 images in all). Put those images through your HDR software and see what happens.

By using only one image you guarantee that nothing has moved in the image. If you still see some images superimposed, your HDR software isn't working properly. If you don't see them, there is some movement between your shots and the HDR process has not aligned them correctly.

Thanks Stefan, will check out your link tomorrow. Will also try another shot without the filter.

Thanks for the info Don, I took 5 images using the K20D's bracketing at 1 stop intervals, all on a tripod and mirror up. I used Photomatix to stitch together. I have tried in the past using just one image as you suggested but always struggle with noise. Always told 3-5 images better. I did think there seemed to be a softness/fuzziness on the 2nd span. May go back to try again but it's about 1 1/2 hours away. Sometime...

Thanks again.

Following this thread why would you need to turn off shake reduction ? What difference would it make ?

When on a tripod there is no shake, so all shake reduction systems start to look for the shake and end up inducing it instead. Every manufacturer instruction book I've seen advises the same - when on a tripod, turn off the shake reduction.

I also suspect that as the Pentax DSLRs clamp the sensor to a fixed position when SR is turned off this probably means the highest precision at that point, so for critical macro work that would be the way to go.

I use the 2 second self timer for tripod shots, so the camera turns SR off automatically.

On a particular day when I had plenty of time on my hands I decided to carry out a few experiments with regard to shake reduction left on or off while on a tripod and I actually did not find any difference in the image quality. Even at macro level.

Having said that you are actually absolutely right, that all manufacturers advise on turning off SR or whatever they are called by other makes while on tripod, but I am wondering if that is probably more to do with saving battery than really deterioration of IQ. I might be wrong though so as a rule I do turn it off while on tripod, when I remember it.

What prompted me to carry out the experiment was because on many occasions I found myself shooting while on a tripod with the SR on, just because I had forgotten to turn it off. But otherwise I always turn it off. I am sure this might happen with other members too, having used the camera with SR on and suddenly putting it on a tripod and forgetting to turn it off, or vice versa which could be more damaging to the IQ.

It also switches off in wireless flash mode but not in normal flash mode, I can't imagine why.

Might be because when using normal flash you have the ability to use slow sync mode, first curtain flash/second curtain flash in which case SR is quite handy as you could use quite low Shutter Speeds in to acquire certain effects.