I'm trying to troubleshoot this issue.

[MWK]

Hi All,

I recently bought a new camera Sigma FP and have attached it to my Polyvar microscope. The issue I have is that I have these dark spots on the image. It would seem that they are dust particles on the sensor, but the sensor is absolutely spotless. Could these be particles between the sensor and 'glass' in front of the sensor (the sensor is usually sandwiched with a piece of glass)?

Would love some help on solving this issue. You can see in the attached photo that there are two types of spots (at different depths), so perhaps on the inside glass (bigger spot) and on the sensor itself (small cluster or smaller spots).

Much appreciated!

[MichaelG.]

With a pixel pitch of just under 6 microns … are you sure about ‘absolutely spotless’ ?
… Those do look like dust to me

MichaelG.

.
Ref. https://www.digicamdb.com/specs/sigma_fp/

[MWK]

If I attach my lens to the camera and test for dust particles, none show up. So yeah, I'm really confused. Is it possible the light/refraction in the microscope is creating these somehow?

[MichaelG.]

Regrettably … Yes
My micro 4/3 camera shows-up dust specks much more on the microscope than it does with the normal lens attached.

MichaelG.

[MWK]

Have you found a way to remove them entirely from the sensor in any way? I want to avoid touching the sensor as much as possible since it is brand new. Blowing air doesn't seem to help at all.

[MichaelG.]

The best I have managed is [working with a stereo microscope] to use a vacuum cleaner with a tiny silicone-rubber-tipped nozzle … the nozzle is an adaptation of a ‘WaterPik’ dental cleaner and, although probably not essential, allows one to work in a slightly more relaxed manner. The ambition being, of course, to never quite touch the sensor.

https://www.waterpik.co.uk/oral-health/ ... s/PP-100E/

It is extremely tedious … and demands working in near ‘clean-room’ conditions !

Another option is to use a liquid which sets to a peel-able film; but I have never used that.

Hopefully, other forum members will offer alternative suggestions.

MichaelG.

[mrsonchus]

Regrettably … Yes
My micro 4/3 camera shows-up dust specks much more on the microscope than it does with the normal lens attached.

MichaelG.

I have found this to be the case also - with a Canon 200D used through 'scope with all the 'proper' Olympus optics a few speck ALWAYS showed-up. From (bitter) experience I've learnt NEVER to attempt to clean a camera's sensor with any method that touches it - I have 100% rate of actually making it worse - every time.....
Having removed the camera from the 'scope to return it to it's use as a 'normal' camera with the Canon lens, I fully expected this camera to have been rendered useless for good photography, having presumed that it was irrevocably ruined by my clumsy actions. The plan being then to sell it on at a cheap price as damaged-goods..

However, to my surprise and delight I have found no trace of these imperfections when taking pictures in the conventional way. This nice little camera is now a keeper for casual photography! They are there on the sensor's (or whatevery covering it may have?) surface, but totally invisible in use!

After the above advice never to touch the sensor, I really do like the sound of the film-forming/peel-away solution mentioned by MichaelG above. This method would perhaps involve no actual touching of the sensor and so no lateral 'rubbing, scratching' call it what you may of said surface, as long as the removal was done very carefully of course. Potentially I think, with the correct peel-away material, this could be an excellent solution?

[MichaelG.]

https://www.sensor-film.com/

They tell a good story

MichaelG.

[Greg Howald]

With most cameras these problems don't show up because they aren't originally designed for microscopy. Microscopy is regulated to an alternative use for manufacturers so such matters are not considered in design or function. Perfectly cleaning a sensor seems next to impossible. The liquid that dries and gets peeled off seems to work best but even that took me three tries.
Greg

[Harold]

Do these spots appear regardless of the objective in use? If so,could those spots be caused by something on your condenser? If the condenser is removable, try loosening it and see if "wiggling" it a bit causes the spots to move.

[MWK]

All objectives give the same result, and moving/wiggling the condenser has no effect. There is a parallaxing effect when I loosen the camera from the microscope and shift it around a bit. That's why I thought maybe the dust is sandwiched somewhere between the protective glass of the sensor and the sensor. But, it could still be on the glass itself. Perhaps the larger spots are on the top of the glass and the smaller dots are on the inside layer between the glass and sensor (close to the sensor but not directly on it). I'm used to seeing these larger spots on my older camera, the smaller cluster of spots is really what is baffling me in the end...

But it makes sense that since these camera's aren't made for these microscopes, they won't work 100% as they should. At least, it's good knowing I'm not alone in this. Thanks for the help/insight everyone!

[Hobbyst46]

One "source" for dust spots in the image plane is filters that are placed near and above the field aperture light port at the base of the microscope. For example if the filter is within a thick sleeve.

[MicroBob]

Hi,
first I would make sure where the the dust sits. When they move when you move a component, this is the dirty component.
These spos show least in normal photography when you take photos with a fairly open aperture. As soon as you close the aperture down to f/22 or even smaller they will become evident. For normal photography I never had much need to clean the sensor, but for micro photography it is difficult to avoid. You don't actually touch the sensor with it's micro lenses but a protective glass that protects it. I have used wet cleaning swabs and got it clean to a quite good level. My recomendation ist to stop at this point and not to become too perfectionistic.

Once on holiday I grabbed onto this cover with sun cream on my fingers! I had lighter fluid in my travel microscopy kit and was able to clean the sensor nicely with it...

Bob