What could be causing this?

[Ewie]

Hey all, not sure if this is the right place to post this question....

I was out taking some sunset/evening shots last night taking several different exposures to compensate for sky and foreground etc etc..

Anyway, when I download the images I noticed some reddish discolouration appearing in the centre of the frame like this;

<a href="http://www.flickr.com/photos/kwozzie_nz/2539236295/" title="What The..? by Ewie_NZ, on Flickr"><img src="http://farm4.static.flickr.com/3190/2539236295_fdef5ecc0b.jpg" width="500" height="334" alt="What The..?" /></a>

EXIF: 30sec @ F11, 20mm (exposed for foreground)

I've looked at the sensor (as best I can) and there is no markings, same goes for the lens I used (Minolta 20mm F2.8)

Can anyone suggest anything? I know it's not lens flare, appears to be a reflection from the sensor on the rear lens element. What do you think?

[Tiberius]

It's a bit hard to see when there's other detail in the frame. Can you take a photo of a blank wall or something so we can see the discolouration by itself?

[Major_Small]

If it only happens when shooting in situations like this (into a light source), then it could very well be some sub-par glass. If you're not using digital or professional-level film glass, or if you're using non-multi-coated filters, that could be the source of your problem.

[wulf]

Light bouncing around in the camera. To some extent, you just have to learn the strengths and weaknesses of your lens. For example, I know that my 70-300mm displays purple fringing when pointing to details against a bright background (eg. branches against a mid-day sky) especially at the 300mm end. I can work round that by picking subjects with less strong light and staying away from the long end when I don't want to miss a shot.

You could also work on the picture in post processing (no cost except time) or investigate more expensive glass (no guarantee that you will never get this kind of thing and lots of money but possibly worthwhile if you must take shots your other lenses struggle with).

Wulf

[Ewie]

If it only happens when shooting in situations like this (into a light source), then it could very well be some sub-par glass. If you're not using digital or professional-level film glass, or if you're using non-multi-coated filters, that could be the source of your problem.

Hi Major, Thanks for your input.

This particular lens is a carry over from my film days and (until now) has been a very good lens, or so I thought. I had heard that some older film lenses did exhibit this kind of thing and it was due to the lack of special coatings that DG type lenses have? In this case I was not using any filters at all.

[Ewie]

Light bouncing around in the camera. To some extent, you just have to learn the strengths and weaknesses of your lens. For example, I know that my 70-300mm displays purple fringing when pointing to details against a bright background (eg. branches against a mid-day sky) especially at the 300mm end. I can work round that by picking subjects with less strong light and staying away from the long end when I don't want to miss a shot.

You could also work on the picture in post processing (no cost except time) or investigate more expensive glass (no guarantee that you will never get this kind of thing and lots of money but possibly worthwhile if you must take shots your other lenses struggle with).

Wulf


Hi Wulf, The light bouncing around in the camera tends to make some sense, it was a cold evening and getting damp quickley as the sun dissapeared so I thought that (perhaps) there might have been a little fogging going on on the rear element.

I did try editing in post but all the colour information in the centre part of the frame is gone apart from shades of red. It's a pity really as this was intended to be the foreground part of the blended image. Oh well, guess I rack it up to experience.

Thanks for your input. :)

[Major_Small]

It could be fogging as well. Bascially, the biggest (IMO) reason to buy lenses made especially for digital cameras (or professional-level film lenses) is the coating. When you engineer something, you basically want to do as much as you can with as little as possible. Make it efficient. The problem is, film is less susceptible to ghosting than digital sensors are, so when they created the lenses for film cameras, they didn't need to coat as many elements as they do for digital. Most of the time it doesn't matter, but in some cases, the difference does show up.