[brbob1]

Just got this lens. Between f 5.6 and f 16 there are three white dots on the aperture ring. I found a very poor copy of the user manual but I not clear what these dots represent. Can anyone help?

Thanks, I can't believe how nice this lens is. It is just like new. Can't wait to try it out.

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[stevebrot]

Nice! My guess would be that the dots are half-stop positions for f/6.7, f/9.5, and f/13.


Steve

[brbob1]

Nice! My guess would be that the dots are half-stop positions for f/6.7, f/9.5, and f/13.


Steve

Makes sense Steve, thanks

[yucatanPentax]

Congrats on your new lens! Agree on the half stops.
One of the most fun things about Pentax is their long compatibility. Be sure to report back!

[Lowell Goudge]

Nice! My guess would be that the dots are half-stop positions for f/6.7, f/9.5, and f/13.


Steve

This is a feature of all Pentax Legacy lenses.

The first and last clicks are full stops, all other clicks are half stops. Most 3rd party lenses don’t have half stops

[stevebrot]

This is a feature of all Pentax Legacy lenses.

The first and last clicks are full stops, all other clicks are half stops. Most 3rd party lenses don’t have half stops

Technically, the first click on the K 500/4.5 is 2/3 stop to f/5.6 followed by half stops until f/16 and a full to f/22. Other lenses where the first stop is other than on a full stop vary a bit. Examples from my shelf:

• First variant ST 55/1.8 has a 1/3 stop to the first click (f/2.0) and half stops all the way to f/16
• Last version ST 55/1.8 has 1/3 stop to the first click (f/2.0), a full stop to f/2.8 and half stops from there to f/11 then a full stop to f/16.
• S-M-C Tak 28/3.5 has 1/3 stop to the first click (f/4), a full stop to f/5.6, and half stops from there to f/11 and then a full stop to f/16
• SMC Tak 50/1.4 is as you described
• Pentax-K 55/1.8 has the same pattern as the last version ST 55/1.8
• Pentax-M 200/4.0 is as you described

To be honest, I was surprised to see the variability given that the pattern as you described is pretty much Pentax "canon".

Interestingly, all of my Vivitars and Adaptall-2 Tamrons have half stops between full stops with a full to the minimum aperture with the exception of my Vivitar 28/2.8 in Exakta mount; it has clicks at all half-stops. The CZJ lenses have clicks at all half stops too. I am pretty sure that the only lens line I have that lacks half stops are my various Rikenons. Even then, I suspect the XR 200/4 and XR28/2.8 are set up the same as their Pentax-M twins.


Steve

(...anyone guessing I am bored silly would be correct...)

[gofour3]

Pentax was always constant with the white dots on the aperture ring, they were always full stops:

Phil.

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[normhead]

That's a nice looking lens. Reminds me of a 600mm Pentax lens, my friend pulled out of closet for me back in 1968. It also was pristine, It was his father's birding lens, but his father, prefessor at U of T and owner operator of both a summer camp and a collection that later became the Canadian Canoe Museum , clearly didn't have much time for birding.

[stevebrot]

Pentax was always constant with the white dots on the aperture ring, they were always full stops:

Phil.

Hmmm...what are the three dots on the Pentax-K 500/4.5 ring (this thread)? (F/5.6, f/8, f/11, and f/16 are labeled as such.)

The image indicates a different rule for the dots (at half stop or full stop values depending on situation).


Steve

[Not a Number]

The manual as illustrated refers to only the "white dot next to the lens' full open aperture value" not all the dots between marked values.

[gofour3]

The image indicates a different rule for the dots (at half stop or full stop values depending on situation).

The manual as illustrated refers to only the "white dot next to the lens' full open aperture value" not all the dots between marked values.

Yep white dot after wide open aperture is always a full stop value. Example above the white dot next to f2.8 is f4.

Phil.

[stevebrot]

The manual as illustrated refers to only the "white dot next to the lens' full open aperture value" not all the dots between marked values.

Yep white dot after wide open aperture is always a full stop value. Example above the white dot next to f2.8 is f4.

Phil.

Yep...and...yep.

I should explain that I had to do an image search to find a photo of the aperture ring on the 500/4.5 before I could suggest an answer to the OP. The sequence is:

4.5 5.6 • 8 • 11 • 16 22 32

Edit: More correctly

32 22 16 • 11 • 8 • 5.6 4.5

...and what looked like one more for minimum beyond f/32.


Steve

[Not a Number]

The manual the illustration was taken from is for the A series lens. Reviewing the photos in the Lens database of 300mm or greater Asahi/Pentaxi branded lenses it seems none of the "A" lenses have dots between any markings other than next to wide open. The need for the "A" pin mechanism places the aperture ring close to the camera mount and the circumference isn't large enough to space out the markings to include dots. So it is no surprise the "A" lens manual does not document these dots.

The same is true for "M" series lenses - none of the 300mm or greater telephoto lenses have in-between markings either. I haven't found a "M" series lens manual.

Some of the "K" series and screw mount 300mm or greater lenses do have dots between the numbers (and rather large diameter aperture rings). However the M, K and screw mount lenses are outside the scope of a manual on the "A" series.

[stevebrot]

The manual the illustration was taken from is for the A series lens. Reviewing the photos in the Lens database of 300mm or greater Asahi/Pentaxi branded lenses it seems none of the "A" lenses have dots between any markings other than next to wide open. The need for the "A" pin mechanism places the aperture ring close to the camera mount and the circumference isn't large enough to space out the markings to include dots. So it is no surprise the "A" lens manual does not document these dots.

The same is true for "M" series lenses - none of the 300mm or greater telephoto lenses have in-between markings either. I haven't found a "M" series lens manual.

The M42 and K-series are a different design both optically and physically than the much more compact M- and A-series successors. In addition, the older versions had full manual aperture with no stop-down coupling on the the mount due to probably to excessive distance and mass of the 10 diaphragm blades.

Some of the "K" series and screw mount 300mm or greater lenses do have dots between the numbers (and rather large diameter aperture rings). However the M, K and screw mount lenses are outside the scope of a manual on the "A" series.

The large diameter of the aperture ring is due to the physical location of the iris diaphragm on these rather large lenses.

[Not a Number]

I'll have to revise what I said. I found M lens and accessory brochures on pentax-manuals.com. The "mid" M brochure shows the 400, 500 and 1000mm with the large aperture rings with intermediate dots. It's more of a sales brochure or catalog rather than a general operating manual so no details are given on the layout and use of features.

So it's only the A series (and beyond?) that do not have intermediate dots