Yet Another So How Did *This* Happen? Moment (Light Leak)

[Andrea B.]

I'm happily shooting away last May. Get a very nice yellow columbine with bee. Cool!

 

 

 

And then this happens in UV.

Only I don't see it until months later.

Oh well. Try again this spring.

If I had to guess, I'd say the viewfinder cover fell off the D610??

[Stefano]

I don't know, I think it looks cool, even if you don't want it in your images.

[dabateman]

You have some odd scan lines there. Are you shooting with a flash or led light?

Its almost looks like the frequency of capture is timed with the scanning of an Led light in electronic shutter mode.

But since you have a bee I am assuming your outside and the ambient light shouldn't do that.

Could be a light leak, could be electronic shutter mode, could be the led going through a frequency cycle, could be your batteries aren't fully charged and messing up your cycle timings.

 

But since I like the color, my first thought was you did that. Just remove the copyright text and you have an interesting image. :)

[Stefano]

It rarely happened but did happed on my phones that photos had some lines/glitches, for some reason. The rate of this happening is about once every several thousands photos.

 

The photos were taken in daylight, so no flicker, no strange frequencies. Also, it isn't memory corruption. I saw this happening in real time on the display the last time it happened. Lasted a few seconds and then fixed.

[bvf]

Yes, that writing all over the image is really irritating.

[Andrea B.]

Are you shooting with a flash or led light?

The UV photo was made in sunlight with no use of flash or UV-LED.

 

I'm thinking that if it was not light leak through the viewfinder, then it might have been some dichroic effect from shooting upward at the flower??

 

There was no band in either the visible or the IR images - only in the UV image.

Here is the IR image made with the B+W 092 filter.

This is just a quick conversion (with an unusual white balance).

Note: If you would like to see just how dusty your sensor has become, make an IR exposure. They show the dust bunnies really well.

 

[OlDoinyo]

If you want a dust map of your sensor, make a pinhole exposure. You will be dismayed at what you will find.

[Stefano]

Or shine a distant point source of light on your sensor. That will work too.

[dabateman]

RawTherapee recommends to create a flat using at least 3mm PTFE over your lens and photos taken at each aperture for each focal length with a good light source, like the sun. Use base ISO to avoid noise. This not only can remove dust bunnies but be used to correct diffraction and lens issues.

 

https://rawpedia.rawtherapee.com/Flat-Field

[otoien]

Flat exposures are a well known technique in astrophotography to compensate vignetting of the lens and potential dust bunnies. However I have never heard about it compensating for diffraction - perhaps a moments confusion of the words? To take flats I use an EL-panel sandwiched with filter films and two milky plexiglass plates (for longer exposure and modified color temperature) assembled into a package that is easy to handle outside in the cold. Flats are taken right after every imaging session before anything hopefully have changed, and the panel is rotated 90° between exposures, which are taken in multiples of four. I typically average 20-40 flats in DSS, but with the D500 it is also possible to do an in-camera master flat averaged from 8 exposures that for instance can be used in RawTherapee.

 

 

 

If just using a milky plexiglass plate in daylight, watch out for short shutter speeds with large aperture lenses wide open . As I have experienced with several bodies, exposures are not critically even at 1/500s and below due to the narrow slit in the shutter curtain moving across the frame at those shutter speeds. With the EL-panel above one I use a Lee #208 film, which is a combination of neutral gray and warming filter as one of the filters to bring shutter speed down into the 1/2-1/10 second range.

[dabateman]

No its just me skipping steps in between in my brain.

 

http://rawpedia.rawtherapee.com/Capture_Sharpening

 

Its part of the best work flow when using capture Sharpening tool, which helps reduce diffraction.

 

Sorry a flat will not directly reduce diffraction.

 

I also see the new Affinity photo version is out and does stacking and new stuff with channels. I have to actually learn one of these days what my software can actually do and how to do it.

 

 

[otoien]

So you are using the flat to sharpen up the dust bunnies?

[dabateman]

So you are using the flat to sharpen up the dust bunnies?

 

I have done nothing as haven't tested this yet.

 

The article I linked to says to take your image at your aperture and focus setting. Then pop on the PTFE filter and take a flat field image. When processing in RawTherapee set the blur radius to zero if you want to correct for dust, at the expense of additional noise. Apparently the aperture and zoom setting of the lens will matter for dust correction. Amd you want ISO as low as you can to avoid too much additional noise.

[otoien]

The last linked page is titled "Flat-Field" and the former "Capture Sharpening", but I do not see any connection between these, but perhaps that is what you mean by "skipping steps".

Anyway the flat field correction in RawTherapee is very capable.