PDA

View Full Version : Long exposure problems with A80


sleeping_tiger_62
17th of December 2003 (Wed), 03:56
I have recently purchased the A80 and it is my first digital camera. My only previous camera was a 35mm SLR which I had been using for 24 years, on and off.

I have been trying out the A80, trying to see what characteristics it has and there was one thing I noticed very obviously.

When I take a night scene, I notice any exposure more than 1 or 2 sec will produce a flare with any red light. For longer exposures, any bright light (whatever the color) e.g. formed into words like the name atop a building, will become just one bright patch.

I have tried all kinds of correction, e.g. setting to different light source correction, making sure the f-no. is at the smallest f/8, having the camera on a sturdy tripod, using the 2-sec shutter delay to ensure no camera shake when the shutter opens, etc, but to no avail.

I have not tried using any filter, e.g. something that reduces the amount of red light, to correct it. This is because I am trying to learn about the nuances of using digital cameras before thinking of how to do something about the effect on the images. I am not too keen about using softwares to correct for the image AFTER its been captured. I like to capture a good image with the camera. (If the words came out as one bright patch, how do you get it to spell out what it was suppose to be anyway with digital post processing?)

Does anyone has the same problem? I do not know if this is a problem with the particular camera that I got (just my luck?), or it is a characteristic of the CCD used in the A80, or its lens design being not so good for red color, or that any digital camera, because of the limitation of the CCD, will have this problem. Is this some kind of spillover/crosstalk of the pixels when they become saturated?

Perhaps someone can share some experience with me.

stduc
17th of December 2003 (Wed), 04:41
I can't say I've noticed the problem - but then again, I haven't been looking for it either. I believe all CCD's generate flare - something to do with electrons jumping around I gather! - Can you post a samle pic with exif data. Meanwhile I'll review some of my night shots.

stopbath
17th of December 2003 (Wed), 07:55
The pixels will overflow into neighboring pixels when overloaded.

Don't forget that the illuminated signs are much much more bright than are the light reflected off the walls.

Can you spot meter the sign? Expose for the sign + 1 or +2 ev to get a good exposure of the light.

You may need too exposures to get the walls and the lights well exposed.

You could also edit the sign exposure shot to bring up the value of the walls (better if in RAW, but still doable in jpeg data.)

Expose for the hightlights when shooting digital. Edit for the shadows...

sleeping_tiger_62
18th of December 2003 (Thu), 04:55
Thanks for the replies.

To understand what I mean, go to the website http://www.dcresource.com/reviews/canon/powershot_a80-review/index.shtml and look at the 4 photos used as examples of image quality on the different ISO settings at 50,100,200 and 400. Take a look at the light. The term 'fringing' was used.

I looked up some data on CCDs which I had come across once. Its called 'blooming' when the pixels saturates and overflows to neighbouring pixels, if I read the data sheets right. Perhaps that's what's happening when long exposures are used.