|
Forum: Pentax Medium Format
01-29-2024, 10:18 AM
|
| |
I hope my comments were not misconstrued. I meant only to point out that if speeds below f/11 were going to be avoided due to some softness, then a much less expensive and weighty assembly would do.
|
|
Forum: Pentax Medium Format
01-27-2024, 08:21 AM
|
| |
Removing all glass that rays don't pass through and reach the focal plane when operating the 600mm at f/11 would yield an f/11 lens assembly with the same performance. Note that this has to be done over the entire field. Wide angle lenses only use part of the physical aperture at any particular angle, so glass removal in that case might only be a small annulus.
Most lens assemblies are compromises over aperture, distortion, resolution, light transfer, cost, etc., so an f/5.4 that was T/8 even with the best AR coatings such that it had enough exotic glass to achieve near diffraction limited resolution at f/5.4 over the entire field might not be as desirable as one with a T/# close to 5.4, less glass, and a little degradation.
|
|
Forum: Pentax Medium Format
01-25-2024, 08:26 AM
|
| |
So one could have a 600mm f/11 optic potentially half the diameter weighing potentially an eighth as much to produce the same quality, at least in the daytime where f/11 is practical.
|
|
Forum: Pentax Medium Format
08-19-2023, 01:39 PM
|
| |
Maybe there is a numbering issue. I don't think 19805 has any images. But 19804 has four.
---------- Post added 19th Aug 2023 at 16:43 ----------
If NZ can censor a video throwing suspicion on the government, perhaps Australia has some reason to block Flicker.
|
|
Forum: Pentax Medium Format
08-18-2023, 09:43 AM
|
| |
I see all of them. Firefox 116.0.2 on Linux Mint Mate 21.2.
|
|
Forum: Pentax Medium Format
08-17-2023, 09:41 AM
|
| |
Where photography turns into art, the art of "touch up" in post gains a more extended meaning when software allows results that would have been impractical for Ansel A.
Thanks for the train views.
|
|
Forum: Pentax Medium Format
08-11-2023, 04:41 PM
|
| |
I was hoping for photographic documentation of the man with seven wives. I guess I'll settle for the excellent shoreline images.
|
|
Forum: Pentax Medium Format
08-09-2023, 08:58 AM
|
| |
In the case of cats, people are underpaid staff.
|
|
Forum: Pentax Medium Format
06-16-2023, 09:32 AM
|
| |
I would vote for this source:
|
|
Forum: Pentax Medium Format
06-15-2023, 08:15 AM
|
| |
The Union Pacific Railroad refurbished a massive one in their Cheyenne Wyoming USA yards -- the antithesis of small touristic. UP: UP No. 4014 - The Big Boy. There are some videos about it pulling tourists across the West on YouTube, etc. No images I've seen, though, achieve the level of Ed's posts.
|
|
Forum: Pentax Medium Format
06-06-2023, 08:49 AM
|
| |
Silicon sensors, like those in the human eye, are capable of being damaged by thermal stress. In the case of cw lasers, the limit is about 1 mW/cm^2. (I don't have ANSI Z136.1 in front of me, so this is from memory.) For narrow pulse lasers, the limit is more like 1 microjoule/cm^2 into the eye. The green display above is likely either cw doubled YAG being thrown around such that the time on the eye is very short, or very repetitive pulsed doubled YAG where the individual pulses are short but weak, so the averaging gets one closer to the cw limit. So I would qualitatively assert (or at least believe) that if it is safe for the unaided eye, it is likely safe for the camera, but keep in mind it is possible for a large lens capturing a direct hit to focus it onto a single pixel, so one gets into the relative "hardness" of eye focal plane tissues vs. that of silicon photodetector cells.
We don't see burn spots in the latter [?] images, so apparently the green shots were safe.
|
|
Forum: Pentax Medium Format
05-25-2023, 10:47 PM
|
| |
I was thinking you were on a higher quality wood dock than that in the image, but that it would still transmit wave slap to the tripod, and that wind turbulence could also cause tripod motion at the pixel size/lens efl resolution. Still water suggests no wind and no wave slap.
Anyway, thanks for the endless great shots.
kas
|
|
Forum: Pentax Medium Format
05-24-2023, 05:49 AM
|
| |
Nice! I guess we can tell what direction you were pointed.
"There are stars in the southern sky
Southward as you go
...."
Besides snake avoidance, I would imagine low wind and waves would be needed to avoid micro tremors at the tripod base degrading resolution.
|
|
Forum: Pentax Medium Format
05-17-2023, 03:10 PM
|
| |
Precession frequency equal the earth's spin frequency might lead to that effect, but tidal forces on the continental plates could return us to the pre-solidification phase of earth's history. I.e., it would be hot times on the Long Gully Bridge. :eek:
|
|
Forum: Pentax Medium Format
03-04-2023, 07:52 AM
|
| |
What a great shot of both pulley and gearing mechanical advantage. Thanks for another tour.
|
|
Forum: Pentax Medium Format
02-20-2023, 10:08 AM
|
| |
Was the large amount of overlap driven by the pano software's needs for successful alignment, or to deal with the gradual change in lighting at sunset?
|
|
Forum: Pentax Medium Format
02-01-2023, 08:20 AM
|
| |
Heh. Your waste bin art would be my wall art, if I had any spare wall.
|
|
Forum: Pentax Medium Format
01-27-2023, 11:35 AM
|
| |
No. 2 definitely adds what is needed.
|
|
Forum: Pentax Medium Format
01-22-2023, 12:46 PM
|
| |
To ease the suffering of any who are presently heat stressed in the antipodal territories, I submit a few shots taken nearby here in southern New Hampshire. Sky has been nearly the same brightness as the snow these past two days.
|
|
Forum: Pentax Medium Format
01-03-2023, 09:04 AM
|
| |
Maybe even divers divers. :D
|
|
Forum: Pentax Medium Format
12-04-2022, 09:01 AM
|
| |
A useful illustration of how color vs. BW can bring forward different parts of an image. BW makes the naked trees starkly present against the sky. Color brings the get-a-way nook lights forward matching the leaves and brush, with the trees seemingly receding in attention getting. Thanks for the educational demo.
|
|
Forum: Pentax Medium Format
12-02-2022, 07:23 AM
|
| |
Pretty good airplane windows, or is there some PP that helps? Because the windows are in the near field, glare from reflections can cause contrast reduction, and because the plastic layers are not flat to wavelength quality they can cause near-field distortion, degrading resolution. Maybe the latter is not observable if the f/no is fairly high and only a tiny piece of the plastic is in the path.
|
|
Forum: Pentax Medium Format
12-01-2022, 09:11 AM
|
| |
Patience on another scale most cannot reach.
|
|
Forum: Pentax Medium Format
11-06-2022, 08:07 AM
|
| |
Nice. No. 2 looks like the sky is on fire and the earth is quaking. Hopefully not a preview.
|
|
Forum: Pentax Medium Format
10-28-2022, 08:15 AM
|
| |
Words fail me. I'll settle for "just fantastic!"
---------- Post added 28th Oct 2022 at 11:24 ----------
I had to look up "Brecon." Thank you for the views of beautiful scenery in the midst of unpronounceable towns.
|
