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Comment by lesjacksons posted on FS: SMC Pentax M 150mm f3.5 - superb at 28/03/2026 - 10:02
Right. Without wishing to derail the thread (it's sold now) ! .....
The OP stated they were unused to old glass - there is no need (or possibility of??) calibrating an old lens. You get what you get.
With 'old glass' you can fall into one or two traps. The first is reliance on the image, as snapped - it will likely be uninspiring. The next is the modern desire for SHARPNESS. Modern glass delivers razor edges, old glass rarely does. And you need to stop down to avoid all manner of ills associated with a particular lens. Let's address each of these:
A snapshot is just that. But if you treat it as the basis for something remarkable .... If you are Photoshop savvy or able to utilise RawTherapy then great. If not, get a (free) copy of Faststone Image Viewer and you will quickly elevate that snapshot into something else! If you have pots of cash then Topaz AI will transform mediocre into stardom. In short, you have to process those images (sensitively) and nearly all platforms will deliver the goods to greater or lesser extent.
Is sharpness the be-all and end-all of image-making? Perhaps the absolute subject needs to be sharp, but the rest of the image? Many old lenses are revered for their 'rendering', which doesn't equate with sharpness. It might be how colours are shown, it might be how the background is handled. For example, there are many 135mm lenses available and every one of them is different, which brings us to 'stopping down'. ....
If you present the camera's sensor with a huge hole (e.g. f1.4) then most of the light rays entering the lens have a multitude of potential paths they can take. A very few will be spot on focus, most will miss by a mile because there is nothing to prevent them going where they will. In optical terms, there is a big 'circle of confusion' Consequently, the image can appear way out of focus and you will reject it. The obvious solution is to make the hole (aperture) much smaller, which will cut out the multitude of competing light paths and only let those that will focus to pass. You will need a longer exposure or a higher ISO and lots more of the image will be in focus - and it will all compete with what you hoped would be the subject!.
Now look at it differently. SOME light rays will be in focus - so capitalise on them. Use live view (and magnify it, maybe) to determine the exact focus on the precise detail of your image that matters most - ignore the rest - it will produce amazing bokeh! Additionally, because the aperture is larger you can see the result more easily and focus accordingly. My personal 'baseline' is the closest edge of whatever it might be. Once that is in focus, you can reduce the aperture to admit more or less of what is there into focus. A gut reaction might be, 'set it to f8'! and a great swathe will be in sharp focus when, in actuality, it just needed f 2.8 reduced to f4 to capture the actual subject, leaving the remainder to optical chance.
Wow. That is a long exposition and some of it might be wrong (?)
On the other hand, Old glass is different but it produces the most wonderful images that the Modern stuff cannot compete with.
"OLD GLASS RULES" - Now it's your turn.
Great advice and you have re-inspired me
Thank you
Comment by lesjacksons posted on FS: SMC Pentax M 150mm f3.5 - superb at 27/03/2026 - 12:05
Great set
Comment by lesjacksons posted on Ripon Cathedral at 27/01/2026 - 17:22
Comment by lesjacksons posted on Canal reflections at 22/01/2026 - 15:51
Comment by lesjacksons posted on Holywell Bay at 19/01/2026 - 14:31
Can i come next time 😃
Comment by lesjacksons posted on Woodland walk with an old friend at 16/01/2026 - 16:19
Liking these a lot
Comment by lesjacksons posted on This Mornings Walk.... at 10/01/2026 - 16:06
Comment by lesjacksons posted on Why use a proper camera when you can do this with an iPhone at 29/12/2025 - 06:03
Simple and Superb - the only two ingredients you need
Comment by lesjacksons posted on Early shift at 28/12/2025 - 14:07
I have to envy you as this time of day doesn't exist for me! Beautiful captures of things I can only fantasize about.
I probably miss so much at the other end of the day though!
Comment by lesjacksons posted on Early shift at 28/12/2025 - 06:09


If it has inspired just one person then it was worth sitting up at night writing it. Thank you Adam and get your camera out. Stick an M42 adapter in there and enjoy your old glass.