[Robinta]

Just looking through some RAW files in Lightroom taken at the weekend, and I have 2 shots with a strange banding effect as per the attached photo.

Hopefully it's easy to see, I've processed the shot slightly in camera RAW to try and make the problem more obvious.

Both the 2 shots with the problem were taken in a sequence of about 14 images that day, both were around 15 second long exposures and shots with shorter and longer exposure times were unaffected (varying from 1/8 sec to over 70 seconds).

The only similarity was that they were both in portrait mode and at 17mm on a Sigma 17-70 lens at ISO 200

For the record I always block the viewfinder on long exposures and there was no direct light behind me anyway.

I did use a lens hood and a ND filter but i've never had this problem before and the pictures taken after were fine too.

I use a Pentax KS1 and have the Slow Shutter Speed NR option to ON.

The shots were in RAW mode.

Anyone have any clues ?

Thanks

Robin

Attached Images

View Picture EXIF

File Date

 

[assassinpenguin]

Is the banding the same in each photo?

[photoptimist]

It looks like something narrow and long entered the frame for a few seconds and left. Was it windy that day? Any chance it was the camera strap? (In portrait orientation with strap hanging down to one side, a bit of wind would loft it over one side of the lens.)

[ehrwien]

since you said you block the viewfinder when taking long exposures, there's still the possibility that light got to the sensor some other way than through the front of the lens or the back of the viewfinder... perhaps somewhere on the camera itself, perhaps through the lens... or perhaps through the filter? Is it a variable ND filter? Was it screwed on properly?

[Just1MoreDave]

My guess is some sort of card reading problem. If the photos are still on the card, try copying them to the computer again. It just looks electronic, not something in the image.

[Digitalis]

This typically happens when light enters through the viewfinder, the internal reflections caused these bands to appear. you should have used the small black and easily misplaced viewfinder shade. Pentax really should use the Nikon style built in viewfinder shades.

Even standing behind the camera can't completely eliminate this effect.

[Robinta]

Thanks everyone

[Basie]

plus 1 with digitalis

That thingy really gets easily misplaced and to use duck tape or something is not the ideal what with the sticky residue. Any other good tips for covering without the original cover?

[BrianR]

I'd also agree with light coming in from the viewfinder. With a strong ND filter, it doesn't have to be sunlight directly hitting the viewfinder to have this effect. It's easy enough to test out.

That thingy really gets easily misplaced and to use duck tape or something is not the ideal what with the sticky residue. Any other good tips for covering without the original cover?

Gaffers tape is a cleaner option than duct tape. I've also wedged a piece of black cardstock* in the hotshoe and folded it down to cover the viewfinder.

*standard issue in my camera bag as part of a macro kit

[Bob 256]

I took some thin (5mm) black polyurethane foam sheeting which I got at a hobby store, and shaped a small rectangle that neatly fits the eyecup of my viewfinder. I attach it with 3m removable poster tape which holds securely but peels without leaving residue (have to renew it from time to time). You can attach a little thicker piece of foam to the center of this "flap" to make a "handle" for easier handling when placing or removing. I stick the flap to a piece of release paper (like postage stamps come on) when not in use which keeps the poster tape fresh and from picking up dust, etc..

[victormeldrew]

Personally I glued a keychain with a lobster clip to the eyepiece cover and I clip it to my tripod bag so it's always there.

[DeadJohn]

Light through the viewfinder has already been discussed. I'll offer another, less common possibility:

Water drops on the filter. If rain or spray landed on the top of the frame, gravity might carry the drops slowly downwards.

[Digitalis]

Water drops on the filter. If rain or spray landed on the top of the frame, gravity might carry the drops slowly downwards

Depending on the coatings on the filter rain droplets would slide down the filter rather quickly - the streaks would be short over a 1/8th second exposure. The lens used was the SMCP-FA 77mm f/1.8 Limited which has a built in lens hood which would shield the filter pretty well. Water is transparent, exactly how are you suggesting rain could leave homogeneously illuminated steaks across the entire image?

[Robinta]

Depending on the coatings on the filter rain droplets would slide down the filter rather quickly - the streaks would be short over a 1/8th second exposure. The lens used was the SMCP-FA 77mm f/1.8 Limited which has a built in lens hood which would shield the filter pretty well. Water is transparent, exactly how are you suggesting rain could leave homogeneously illuminated steaks across the entire image?

Due to lightroom throwing a wobbler, the lens isn't the 77mm Pentax, but sigma 17-70.

Still used with a lens hood. No water on the lens and the shots of 30 secs and 1/8 second I also took were unaffected. I really think it's light in the viewfinder

[Digitalis]

I really think it's light in the viewfinder

It is. I have seen this effect occur in images of my own with pentax and canon cameras.