John that's not a pinhole lens at all. It's a single element fixed aperture lens. 11.5mm F/9.

A pinhole has NO lens, and will typically be F/128 and can be significantly smaller
IIRC optimum aperture depends on wavelength & the distance from the sensor & changing the distance from the hole to the sensor adjusts the angle of view produced, but doen't affect focus. Very different charcteristics.

Pinhole images are always somewhat soft. The issue is less significant as you go to larger film formats. Your results are about typical for APSC.
Their big advantage is the near infinite DOF, so fopr best effect you need to make use of that & have part of the view very much closer to the camera

[quote:3496ace15f="Nakedgun"]Went to the Salvation Army thrift store yesterday: Manfrotto 055 with 3130 fluid head.
No shortage of tripods at my place, but, for $3.50? OK.
quote]
Either the head or the legs would be a worth over 10 times that on their own! I hope you donated the change to them.

Welcome Jerry!
Nice to see someone else from this corner of the world - I'm only about 15-20 miles away.
Look forward to seeing some of your shots

Many years ago I took some handheld with ISO1000 film that I thought looked reasonable, more recently I've found longer exposures with a tripod are much better. Moderately wide angles probably work best - with these at 100m distance infinity focus should be close enough.
Given your lens selection I'd probably use the 18-135 in manual mode.
This one: https://www.pentaxuser.com/photo/revised-jubilee-fireworks-48554/large taken at 15s f/16 ISO 100 is my favorite.

Having used a 600mm lens on a µ4/3 mirrorless I can assure you EVFs can work just fine with long lenses. The EVF is also just as good in bright light & actually better than an OVF in very poor light.
Some mirrorless cameras have more physical controls than many DSLRs. My G5 is certainly more easily controlled than budget Canon models, and the number of controls is not far behind my K7.
There are adapters allowing EOS lenses to be used with AF on µ4/3. Add to that the native glass & numerous other MF adaptable mounts the range of lenses available outnumbers any DSLR, even without loosing AF.
I've never managed to get anywhere near a half decent photograph of flying dragonflies with my DSLRs, on the first effort I got quite a few respectable shots with a mirrorless, (actually the first generation G1) so I'm not sure your claims for response & shutter lag hold water either.

Yes I still prefer my K7 for motorsport & airshows, but for most other occasions the mirrorless win due to portability.

At our photographic workshop session last night we had three Pentax users. I think there were 5 Nikon users, and about the same Canon.
It was probably atypical in those proportions, there were several Canon members missing and at least a couple of Nikon users. However I'm pretty sure there have been weeks where Pentax has outnumbered Nikon.

There are many factors that are not so easily quantified. Yes, different lenses can give different colours, there is also the bokeh (rendering of out of focus highlights NOT as some seem to thingk just DOF), and even just the feel of the lens.
Some have (mainly AF lenses) very short focus throws, others much more gradual making manual focusing more precise,

I use my lenses beyond the normal visible range, and differences here can be very marked. Many newer lenses transmit Very little UV (and only specialist ones ever tranmit much there). Infra red transmission also varies wildly, and with some cameras this can sometimes affect the colours in some lights.

Different wavelengths will focus at different points, most lenses are designed so red & blue both focus at the same distance with the other wavelengths being close (called Achromatic). Some more expensive models are designed so that three wavelengths focus at the same point (APOchromatic) This variation is one of the factors determining 'sharpness'. Going beyond the standard visible range many lenses show considerable focus shift, sometime Apochromatic lenses can be worse here.
If a graph of focus distance vs wavelength is ploted a lens could have a relatively straight line, an achromatic lenses will give a quadratic curve, and apochromatics a cubic (S shaped). The ideal would be a horizontal line. It is actually possible for an Apochromatic lens to have some wavelengths that are quite a long way form the set focus ( a steep S) Low dispertion indicates a flatter plot, giving less chromatic aberation.

The point of having variable aperture is to select the aperture appropriate for the shot. Yes the lens is not intended for use only wide open and sharpness will improve when stopped down. Comparison with the DOF & bokeh of normal/telephoto lenses is hardly relevant, they have a completely different FOV, and give very different compositions.

The OP suggests Pa has a need to use his lens at ~f2.8 & wants to know the sharpest options for that. Telling him to stop down is not going to solve his problem. If it's for shooting the night sky, bokeh will not normally be relevant & stopping down can cause a host of other issues (star trails/noise...).

The spring MUST be removed. If the plain bayonet bothers you it's not difficult to file or drill a small hole/grove in the right spot for the locking pin. I did this the first couple of times, but haven't bothered since. If the adapter is a fairly loose fit arraging a locking point is certainly a good idea.