[Zig]

Yes, that is an aperture of f45(forty-five).
Obviously it is usually only longer focal length lenses or macros that have these very small apertures so as to maximise depth of field.
The trade-off is that by the time diffraction has not just set in but bought the house and let out rooms, "image quality" nominally suffers.
And I say "nominally", as some photographers find this lo-fi and low-resolution stuff has its own unique effect.
Coupling this phenomenon with a really crunchy high ISO setting has the immediate advantage of allowing small apertures to be used handheld...the resulting noise can be quite grain-like, depending on the sensor one's camera has.
My relatively ancient 1Ds2 can be whacked up to 3200 but its normal high is 1600, so I thought I'd try an experiment:
I knew that sharpness would not be present(!) yet all manner of textural goodies might be, so in these shots of poppy fields I aimed for a more, er, impressionist style, relying on tones, colour and composition to stand in the stead of resolving power: cos, let's face it, a maxed-out ISO'd IDs at f forty-five doesn't have any!

As you can imagine, being freed up from any temptation to stick with optimum aperture in order to pixel-peep, is very liberating...also oddly "focusing" in a way: one knows that detail will be supplanted by texture...so one's eyes are being trained to look at the textural and wider swathes of compositional interest.
And given that last point, then, that's not a bad thing for any aspiring shooter.

In this case, "post-processing" is again a matter of trying to work with the front end: attempts to retain sharpness when downrezzing are a bit redundant, so all manner of tonal experiments can be freely explored....I had a play with saturation, given that subliminal feeling of impressionism or even pointillism(yes, the noise is that whacky!)
For the icing on the cake of course, shooting thus at one's absolutely worse focal length is a must...so of course I went to 280mm wherever possible!

[NT73]

Ooh those poppies are hurting my eyes. Not so much in the last one though.

[nia]

No.2 and 4 are my best. The colours are so strong, but so nice too. Especially the mist in no.4 fascinated me, but the colours of the poppies are not the original colours of them, aren't they? If they would be original, would be more impressive with the mist behind the trees... Just an idea. Thank you dear Zig,

with my love,
nia

[Toad]

To be honest, I'm not sure what to think about these. I find the effect kind of interesting - and I think it works really well in #1 and #4 - or possibly, the combination of other processing and the technique works well. I particularly like the brushed vignettes and color mods in #4.

The gradient sky in #1 also is quite effective - as it cools down the heat that the rest of the photo generates. In #3 and its crops, I find the noise in the skies a bit distracting. Your vignetting in #4 masks that quite nicely.

Its an interesting technique and I can see how it would be a nice one to have in your bag of tricks for the right photo. So what lens of yours goes to F45?

[matthew]

Interesting approach, and a good example of the difference between actual peak sharpness, typically a couple stops down from wide open, and the extensive visual information from an image with massive depth of field from working at the other end of the aperture range. If nothing else, it does show that diffraction isn't something to be avoided at all costs – there are plenty of times when the trade-off is worth making.

(On a completely different tangent, I've taken more photos at f/45 than at f/2.8 with my 85mm PC-E tilt-shift 'macro' lens, although both are a tiny fraction of the total photos that I've used it for.)

[Zig]

I shot myself in the foot rather, as I really should have overcome my laziness and had a grey card and some front-end calibration going, as things went a bit nuts even with "straight" conversions; still, like the curate's egg, good in parts.
Toad, it was the 70-200 that went to f45....or f45.3 should I say. It was news to me, I have to say!