Test subject for objectives

[TonyT]

Diatoms are somewhat of a standard subject for testing the resolving power of an objective. Not always readily available at a cheap price.
Fly wings are a reasonable substitute. They are flat, easy to obtain and mount on a slide.
Although they appear to be featureless membranes stretched between veins they do have fine structure. A 40x objective should be able to clearly resolve the fine hairs on the membrane and the longer hairs on the edge of the wing.
This small housefly-family fly (Caricea sp.) is common locally and is active in late Winter on the 1st warm day (yesterday!).
Wing images with an Olympus BH2/BHS and imaged with a Nikon D810.

[MichaelG.]

Very impressive, Tony

MichaelG.

[dtsh]

What is your method for mounting them?

[apochronaut]

Diatoms have somewhat standardized features, which can be related to resolution. Striae gap width, punctae diameter for instance. In the absence of such criteria for a fly's wing, one can only get a vague impression of the optical quality of an objective, not a quantitative impression. This is also compounded by post processing and details such as whether the image was a stack etc.

[PeteM]

Impressive images, TonyT.

[Hobbyst46]

Diatoms have somewhat standardized features, which can be related to resolution. Striae gap width, punctae diameter for instance. In the absence of such criteria for a fly's wing, one can only get a vague impression of the optical quality of an objective, not a quantitative impression. This is also compounded by post processing and details such as whether the image was a stack etc.

For non-entomologists, how easy is it to identify a randomly-obtained fly, and find quantitative typical features ?
The most studied fly is Drosophila, I guess, but how common are they, so what are the chances of getting one away from orchards and plantations ?

[Seta]

Subjects like this are good to test lenses for CAs, those black hairs against a bright white background can be a colourful nightmare.
Unless you have fixed them is software those Splans do perform pretty well, better than the nikons CFN I am using.

[TonyT]

Thanks for all the comments.
These are stacks, using Zerene; and no, there has been no software correction for CA.

Simple mounting: one wing removed using 2 pairs of #5 forceps - my favourite equipment for dissecting small subjects.
Placed wing on a flat slide
Added a tiny amount of liquid to just wet the wing. I used 99% IsoPropyl Alcohol. Added 1 drop of Canada Balsam (I could have used Euparal).
If you are using a water-based medium then wet with water.
Added a coverslip.

Drosophila is a common fly here, at least in Summer. Buy one banana, leave it indoors to get really ripe; Drosophila turns up like magic!
Lucilia spp., greenbottles and bluebottles are found just about everywhere.

[tgss]

Yet more very nice images indeed.
Thanks again for sharing.
Tom W.

[Stomias]

Very impressive!

[apochronaut]

Diatoms have somewhat standardized features, which can be related to resolution. Striae gap width, punctae diameter for instance. In the absence of such criteria for a fly's wing, one can only get a vague impression of the optical quality of an objective, not a quantitative impression. This is also compounded by post processing and details such as whether the image was a stack etc.

For non-entomologists, how easy is it to identify a randomly-obtained fly, and find quantitative typical features ?
The most studied fly is Drosophila, I guess, but how common are they, so what are the chances of getting one away from orchards and plantations ?

It isn't. That's my point. Diatoms have definable structures that measure an objective's performance, if interpteted well.