Forgot Password
Pentax Camera Forums Home
 

Showing results 1 to 25 of 300 Search:
Forum: Pentax News and Rumors 2 Days Ago  
"3 way" binocular and monocular projects
Posted By kwb
Replies: 51
Views: 6,750
Since the last post I have found that the focus distance with the macro stand could be changed by a large amount by turning the green focus range ring on the monocular. Of course DOF is still super thin, but at least you can focus on something that is higher than the plane the stand stands on.
I completely forgot that the ring was there because the monocular itself covers 1.5m (about 5ft) to infinity with the ring at "Normal" position and that's all we need when we go for a walk. If you want you can go as close as ~70cm (~27.5") but it seems that we didn't feel the need and the ring was stuck at "Normal" all the time.
I understand. But you don't need a cellphone to enjoy the macro stand, the performance of the stand with the monocular is pretty impressive for visual observation, and ergonomics without cellphone is great.
Forum: Pentax KP 5 Days Ago  
Post Your Best KP Shots
Posted By kwb
Replies: 2,585
Views: 251,373
This is from last July when I and my wife were walking down a small mountain nearby after the sunset. We scared off many of these birds sleeping on gravel, we couldn't tell what they were as they looked like dark blobs to our eyes, but I managed to take a few shots. I thought that I totally screwed up the exposure, birds were still dark blobs on the rear LCD. Well, screwed up I might have :lol:, but RAW image from KP had more room for PP than I thought. In the end we were happy not just because we saw that they were horned larks, but because we actually liked one of the pictures.


KP and 55-300 PLM at 300mm f/6.3, ISO1600, 1/40 sec. PP included boosting brightness by 2.5 stops among other things. I have to say I love KP for AF in dark places, SR that's good for 300mm 1/40sec on a crop sensor and low noise output that allows me to massage things in post even if I underexposed by 2.5 stops.

Horned Lark in twilight by k kwb, on Flickr
Forum: Pentax Compact Cameras 5 Days Ago  
Point and Shoot Competition #151 - Shoot Anything!
Posted By kwb
Replies: 13
Views: 864
Great entries everyone!

Mine were taken in my evening walks in my neighborhood. The first one shows beavers' work shot with google pixel 3 in panorama mode. At some point people put protective steel guard fence around each of the remaining trees. I have no idea how beavers could bypass those, but somehow they always outsmart people.

The second one is Pentax Q7 with 06 telephoto at 33mm, f/4, ISO 100, 1/800 sec.
Forum: Pentax Q 6 Days Ago  
0.5x wide angel attachment? or C-mount wide angle?
Posted By kwb
Replies: 58
Views: 12,473
Welcome srsly, you waited for a long time didn't you! :)
It seems like there's still a demand for the original Death lens. Petition · SAVE THE CENTURY OPTICS MK1 FISHEYE! · Change.org
I cannot find the spec of Baby Death from Century Optics, I can only guess that it's not as wide as 0.3x if it was smaller than the Death lens. Thanks for the trivia!
Forum: Pentax News and Rumors 10-18-2020, 10:58 PM  
'Be patient and wait' (Kimio Tanaka)
Posted By kwb
Replies: 148
Views: 11,131
OK, now I have some time, so here it is.
我慢して待つか。 = "I guess I'll be patient and wait."
No "We", no "have to".

我慢して = be patient and
待つ = wait
か = conjunction "or", it could also indicate some sort of question/selection when combined with a verb.
When used in a subject-less sentence where the subject is the speaker/writer, this is a casual statement of intent in the form of rhetorical question/selection (something like "I shall wait shall I?" but lesser stress on will/determination, he just thinks that's what he'll do). This is a usage pattern you'll see quite often. When you're thinking about dinner and just about to decide to cook a burger, you might say to yourself ハンバーガーでも食べるか, or "well I guess I'll eat a burger".

Is the subject Tanaka, though? Yes. When addressing somebody other than the speaker/writer, the same sentence could be interpreted as "shall we wait?", but that's an impolite form of the question and you never ever speak to strangers like that.
Forum: Pentax News and Rumors 10-18-2020, 08:54 PM  
'Be patient and wait' (Kimio Tanaka)
Posted By kwb
Replies: 148
Views: 11,131
He isn't. The title of this thread is not what Tanaka wrote. I'll explain later.
Forum: Pentax News and Rumors 10-16-2020, 09:20 PM  
"3 way" binocular and monocular projects
Posted By kwb
Replies: 51
Views: 6,750
I never tested the cellphone adapter until yesterday, here are some examples with and without macro stand.

The bee/basil picture was shot without macro stand, so this is a telephoto configuration. As you see the image circle is smaller than the field of view of the phone, so you probably want to crop on the phone by digitally zooming. Though I don't have any experience with any other telephoto "adapter" for phones, 1:1 crop looks pretty good to me for a cellphone picture. The third picture was shot from roughly the same position as the previous one but without the monocular to show you how far I was from the bee. Oh, the cellphone is google pixel 3, these are in-camera jpeg (down-sampled or 1:1 crop using lightroom).
I was NOT using an eyepiece hood (comes with the kit) to block the ambient light, i.e. there was a big gap between the monocular eyepiece and the cellphone lens. Yes I'm lazy. I used my hand to block as much light as possible but the black area outside of the image circle in the first picture is not really black, I suspect that the contrast could have been better if I used the hood.
One serious drawback of this is, since the phone screen is REALLY off to the side of the optical axis of the monocular, and since this was a fairly long telephoto looking at a close range, it wasn't easy to figure out where I was pointing the lens at. This was less of a problem when shooting an object really far away.

Salt crystals as well as PF Marketplace on the ipad screen were shot with the macro stand. I used built-in LED lights for the former. It's sharp at the center but quite out-of-focus and also with significant yellow/blue fringes as you go closer to the edge. This might also be dependent on the phone and how well the phone's optical axis is co-aligned with the monocular's. FYI, that " Marketpla" is about 7/16" or 11mm wide on my ipad.

You can only focus at around a plane where the macro stand is standing on, you cannot really change that by moving focus rocker, and DOF is really thin. I tried to picture a tiny basil flower and it was impossible to keep everything reasonably well focused (not shown). And forget about macro of moving creatures.

The phone clamp allows the phone to slide sideways, and the thumbscrew could be loosened to move the phone up and down (6th picture). Adjusting the phone-monocular alignment this way is cumbersome, I need at least a minute or two of trial and error, you start over each time you attach the phone, and this is equally true for telephoto configuration. This is definitely NOT something for "hey what's that bird, take a picture now!" type moments. Since my cameras are more convenient for that kind of thing and are ergonomically much better (look at the last photo), I think my usage of the cellphone adapter will be limited, but I have to say it's kind of fun to look at tiny things on the phone screen that is MUCH better than my camera LCD once everything is set up properly.
Forum: Pentax Q 10-11-2020, 12:21 PM  
Anyone have 2 or more Q's?
Posted By kwb
Replies: 28
Views: 2,303
Interesting that an old thread suddenly comes back to life like this!

I have two Q7 (black and yellow), 01, 02, 03, 06 and 08 lens, and some adapters including Pentax OEM ones. Sadly, LCD of my black Q7 developed two "dead" pixels that are always bright green regardless of the camera state. OK for using menu but distracting when framing. I still use that camera but I'm happy that I bought two.
Forum: Photographic Industry and Professionals 10-10-2020, 11:59 AM  
Marketing K-New
Posted By kwb
Replies: 44
Views: 2,141
Pretty much just social media in USA (Facebook and twitter).

In Japan,
Forum: Pentax Compact Cameras 10-01-2020, 08:05 PM  
Point and Shoot Competition #150 – Mysterious things in and around your home town
Posted By kwb
Replies: 21
Views: 1,163
Congrats barondla, Bart and David! Thank you gbl for an interesting competition!
Forum: Pentax News and Rumors 10-01-2020, 09:12 AM  
Ricoh Imaging appointed global spokesperson
Posted By kwb
Replies: 101
Views: 8,505
Oh noes, silly me. Hard to imagine that Li Xian is somehow related to Oinions originated from 1880's Illinois. :lol:

Oinion Name Meaning & Oinion Family History at Ancestry.com®
Touché!


Thanks for this, my research about KOL wasn't wasted after all.
Forum: Pentax Compact Cameras 09-30-2020, 11:00 PM  
Point and Shoot Competition #150 – Mysterious things in and around your home town
Posted By kwb
Replies: 21
Views: 1,163
Lots of mysterious ones, everybody!

Mine is not a great mysterious picture but is about how I unintentionally created a mystery to my neighbors using mystery money. Took it on March 31 this year using google pixel 3.

I found a ziploc bag with 20-something USD inside in front of my house. I didn't want to steal it, so I taped it to my garage door facing the street. That was ugly and hard to miss, if a kid dropped his/her charity money or something like that, that person would certainly recognize and take it, I thought. I posted the image to a local facebook group and waited.

Two weeks have passed without any taker. When I went out to check my mail box, one of the neighbors came out and asked me "Hey, what did you tape there, it's money isn't it? What's that about?" She sounded really curious but I saw a bit of seriousness in her eyes. As soon as I explained, she started laughing. She said she and her husband have been wondering for a long time if that was some "charm for good luck" or some such. Probably they thought that we were trying to repel COVID by Japanese voodoo. :lol:

In the third week I gave up and gave that money to charity.
Forum: Pentax News and Rumors 09-30-2020, 04:58 PM  
Ricoh Imaging appointed global spokesperson
Posted By kwb
Replies: 101
Views: 8,505
Is it a common practice to call somebody a "global"-something for local marketing purpose in China? I googled around and found that the Chinese subsidiary of Shiseido, a large Japanese cosmetics/skin care brand, appointed a Chinese-born American actress Liu Yifen as the "global ambassador" back in March this year.
????????????????????????_?????
She apparently played Mulan character in the Disney movie so she should be more famous outside of China than Li Xian, but my googling didn't find any marketing effort by Shiseido using her outside of China. I still don't know if this is a common practice or not but certainly it's not unheard of.

Anyway, if the Chinese subsidiary of Ricoh Imaging, a business to sell things to Chinese market, think that they can sell more if Li Xian is called the global ambassador rather than just an ambassador, more power to them.

BTW I found this advertisement article written by a marketing agency in China to tell you why it's important for luxury brands to choose Key Opinion Leader (KOL) like Li Xian as the brand ambassador to appeal to young Chinese consumers. (I didn't know what KOL was, now I know and feel as if I didn't have to, so I had to let you know too. )
How Brands in China choose their brand ambassador? - Chinese Tourists Agency

That was published on Jun 20 2020. That might be a coincidence or not, but it certainly shows that the Chinese subsidiary of Ricoh Imaging carefully chose Li Xian, the cool young Key Oinion Leader representing new Chinese values, as their ambassador.
Sounds like it.
Forum: Photographic Industry and Professionals 09-20-2020, 01:14 PM  
Pentax K-3 II successor on September 2020
Posted By kwb
Replies: 961
Views: 82,727
There are some businesses that adopted it but they are a minority. My parents in Tokyo didn't know what Black Friday was when Amazon started Black Friday sale in Japan last year (but since Amazon did it, I expect more online retailers will do it this year).
We don't observe Thanksgiving in Japan so it's hard to remember the date. For that matter I don't remember/know if Japanese retailers were doing it on the same day as American retailers.
Forum: Pentax News and Rumors 09-19-2020, 01:12 PM  
"3 way" binocular and monocular projects
Posted By kwb
Replies: 51
Views: 6,750
And my Pentax VM 6x21 monocular premium kit was delivered yesterday. This is for my wife when we go for an evening walk, but the air quality has been terrible due to wild fires (seemingly everywhere these days in the west coast of USA) in the past two weeks and so no walk yesterday.

First, very strong pros that we cannot be happier about.
  1. Rocker mechanism for the focus adjustment is convenient and works extremely well. It moves smoothly but with the right amount of drag, giving us the feeling of robustness. This is the feature that attracted me most, and I'm glad that they got this one right.

  2. It offers clear and bright view as advertised, with good eye relief.

  3. Macro stand works better than I thought with its own lens and two bright LEDs. But we haven't tested a cellphone to take pictures yet.

  4. Nice exterior design and material texture.

Now, cons. The first one could be serious for others though we're OK with that. The second one is kind of serious.
  1. Cellphone adapter doesn't work for my wife's 1st gen iphone SE, that phone is too small. The claws that grab the phone only closes down to 61mm or so, but 1st gen iphone SE is only about 59mm wide. I should have checked Ricoh Imaging Japan's product page more closely (http://www.ricoh-imaging.co.jp/japan/support/faq/images/binoculars_img_01.jpg), this information wasn't available on Ricoh Imaging USA's web page or if it is I couldn't find it (I'll report them). It's OK for us as we can still use my cellphone, but anyway.

  2. No lens caps for storage. The case offers some level of protection but the lenses are still exposed.

  3. Monocular is connected to the macro stand using bayonet type mechanism (just like a lens and a lens hood), which is nice. However, that bayonet thing on the monocular objective is usually covered with a rubber ring which we will eventually lose.

  4. We'd have liked a neck strap rather than a wrist strap. We'll probably use Pentax Q7 neck strap that I never use for Q7.

All in all my first impression so far is very positive overall.
Forum: Pentax News and Rumors 09-12-2020, 04:31 PM  
Patents possibly linked to the APS-C flagship
Posted By kwb
Replies: 108
Views: 11,737
Good question. There could be two things, I'll start with the one that probably has a bigger effect.

Reason 1.

Through a higher refractive index material, the focusing screen looks closer to the ocular lens. This is not just an optical illusion in that the higher the refractive index, the larger solid angle (Solid angle - Wikipedia) of light originating from any given point on the focusing screen reaches the ocular lens.

Forget about the prism shape, it's just a hunk of glass with one input surface and one output surface, reflections don't have anything to do with refraction. Instead, let's think about a point on the focusing screen, an empty space, and an ocular lens (Figure A). The point P emits light in a wide angle, and only a fraction of that reaches the lens. In this figure, I used the apex angle of cone of light that reaches the lens instead of the solid angle to represent how wide the cone is.

Next, without changing the distance between the focusing screen and the lens, fill the space with a glass plate with parallel surfaces (Figure B). Because of refraction, the apex angle of cone of light at P that reaches the lens is larger than before. From the lens, the focusing screen appears to be at a new location P', and the apex angle viewed from the lens is the same with the apex angle at P. The larger the refractive index, the larger the apex angle, thus the larger fraction of light from P reaches the lens to be relayed to the eye (thus brighter).

Suppose that you have two glass plates of the exact same thickness, one made of typical glasses like BK7 (n=1.516) and the other made of Ohara S-LAH66 (n=1.7725) that is one of the high refractive index materials mentioned in the patent. How much more solid angle do you gain by using the latter? Let's calculate the ratio of the solid angle!


It turns out that you don't need to know the exact dimensions for the calculations. As far as most of the space is filled with the glass (i.e. distance between the focusing screen and the pentaprism as well as between the pentaprism and the ocular lens are much smaller than the apparent path length of light), and as far as the ocular lens diameter is smaller than the apparent path length of light, the ratio is pretty much the same.
And that ratio is,
  • solidAngle(S-LAH66)/solidAngle(BK7) ~ 1.37

(for example if the entire space between the focusing screen and the lens is occupied by the glass, the ratio is ~1.369 when arctan(R/d)~5 degrees, 1.376 if arctan(R/d)~10 degrees).
That is, assuming that the reflection at the input and output surfaces are negligible in both S-LAH66 and BK7 because of good anti-reflection coating, 30-something percent more light reaches the ocular lens originating from P.

Note that this is an optimistic estimate and should be considered an upper limit. In reality, though the light is indeed emitted with a large angle from P, the light intensity is not distributed evenly to all directions (e.g. the light is stronger at the center of the cone) and therefore the ratio of the light energy (number of photons) is somewhat smaller than the ratio of the solid angle. There could be other gotchas. 37 percent could easily be 30 or even 20 percent. But this is NOT a few percent effect.

But the view is larger in the new VF, thus increase in the photon number is distributed over a larger area for your view. This will counteract to make your view dimmer. Using the square of the magnification ratio, this effect is
  • mag(K-NEW)^2/mag(K-3)^2 = (1.01/0.95)^2 = 1.13.

Ratio of brightness per area on your retina is therefore
  • brightness(K-NEW)/brightness(K-3)~ 1.37/1.13 ~ 1.21.

Wow, 20% brighter, maybe this is too much but as an optimistic estimate that should be considered an upper limit, I claim success.

Reason 2.
The higher the refractive index, the smaller the critical angle (Total internal reflection - Wikipedia), therefore smaller transmission on roof surfaces for angle of incidence (AOI) smaller than the critical angle. (FYI if AOI is larger than the critical angle, light is 100% reflected without transmission.) This is something that is very briefly mentioned in the patent. There should be such an effect, but it's hard to imagine that this is a huge effect that can possibly explain 10% brighter VF.
The reason why I don't believe this to be the dominant effect is because the AOI on the roof panels is already larger than the critical angle even for BK7 for the vast majority of rays. Critical angle for BK7 and S-LAH66 are 41.3 degrees and 34.3 degrees respectively, while the AOI on roof panels for the light perpendicular to the input surface is 49. 2 degrees.



Wow, ogl didn't call people liars as far as I see. And no, actually it's not explained in the patent, the patent is not about the brightness of the VF per se.
The patent is about the recipe for multi layer dielectric coating on the roof panels of the roof pentaprism and other prisms with a roof. Without coating, the view quality (contrast and sharpness) suffer, regardless of the refractive index and brightness, according to them. Prior art exists for regular glass materials like BK7, but not for higher refractive index materials, thus this patent.

Sorry for long post!
Forum: Pentax News and Rumors 09-12-2020, 02:46 PM  
Patents possibly linked to the APS-C flagship
Posted By kwb
Replies: 108
Views: 11,737
Hi gaweidert, the shape and the size of a pentaprism is not dictated by the refractive index.

You don't want to change relative angles between surfaces of a roof pentaprism regardless of refractive index, because these define the function of the prism. Ridge of the roof is 22.5 degrees tilted relative to the input surface, roof panels are orthogonal to each other, internal bisector of the roof panels is orthogonal to the input as well as the third reflection surface, the third reflection surface is tilted 45 degrees relative to the roof ridge, and the output surface is orthogonal to the input surface.
You can make the overall size bigger or smaller, or make some surfaces closer to or farther away from other surfaces. This is bound by physical constraints like the size of the focusing screen (which is ultimately determined by the sensor size) and the position of the ocular lens (which is ultimately determined by the position of human eye), and by practical considerations like the size of the prism as well as the ocular lens system.

You can shape a roof pentaprism exactly like the one in K-3 using higher refractive index material, put that in K-3, and the new pentaprism still works in that it relays the light from the focusing screen to your eye without problem (actually better than the old one in a sense as I'll explain in my reply to ogl later). Of course the focusing screen "looks closer" viewed from the ocular lens due to larger refractive index, just like fish looks closer in water than it physically is. Existing diopter adjustment might not be enough to compensate for that, and you'll want to to change the ocular lens parameters. But the shape of the prism doesn't have to change just because of different refractive index.

BTW, roof pentaprisms are reflective prisms (reflective prism - Wikipedia), not dispersive ones (dispersive prism - Wikipedia).
By design, exit angle of light on the output surface is ALWAYS the same as the angle of incidence on the input surface regardless of color for reflective prisms. Among other things, this means that refraction effect of reflective prisms is equivalent of that of a glass plate with parallel surfaces (while that of dispersive prisms is equivalent of a wedge-shaped glass plate). Unlike dispersive prisms, reflective prisms don't separate co-propagating rays of light into different directions depending on color.

That's not to say that there's no dispersion ( Dispersion (optics) - Wikipedia ) effect in reflective prisms, but since that does NOT cause angular difference depending on colors, it's not that big of a deal for focusing systems like viewfinders, just like using an ND filter or UV filter, which are glass plates, won't give you color fringes for you camera, or looking through a glass window won't give you a rainbow-colored world for you to enjoy. The effect is there but is to small to matter.
Forum: Pentax Q 09-10-2020, 04:52 PM  
Let's share shots with Q!
Posted By kwb
Replies: 6,459
Views: 1,005,897
I like jumping spiders. This one was scouting from behind the window lock in our bedroom.

Behind the Lock by k kwb, on Flickr

This was shot with Q7, Vivitar Series 1 VMC F2.5 macro for Canon FD mount at F/9, and a dedicated Vivitar 1:1 Macro adapter which I think is a 2x teleconverter, therefore combined with the lens it's F/18 in reality (!!).

BTW, this might be a good example of why I don't worry too much about blurring due to diffraction. I like this picture anyway even if this is not THE sharpest picture I can take with my existing lenses in theory.
Forum: Pentax Q 09-09-2020, 08:27 AM  
Let's share shots with Q!
Posted By kwb
Replies: 6,459
Views: 1,005,897
Oh, that's Q7, BORG 55FL and Pentax 1.7x AF adapter (though of course AF doesn't work on Q7). This setup gives me 425mm f/7.7.
Forum: Mini-Challenges, Games, and Photo Stories 09-07-2020, 12:00 AM  
Thematic Show me your ......MOON !
Posted By kwb
Replies: 889
Views: 71,225
That's nice ecostigny! And at least your Mars was closer to your moon than mine! :) This is from my back yard in WA, USA.

Shot with BORG 55FL (small 250mm f/4.5 telescope) and Pentax Q7, ISO 200, 1/80 sec. Turbulence was bad, I took a bunch of pictures (turned out I shot 78) and manually selected the one where Mars looks reasonably round.

This one is from earlier this week where the low moon was really red behind thick haze and thin cloud. Haze was probably due to fire 60-70 miles away. Pentax Q7, BORG 55FL and Pentax 1.7x.


Both are cross posted to Let's share shots with Q! - PentaxForums.com thread.
Forum: Pentax Q 09-06-2020, 11:27 PM  
Let's share shots with Q!
Posted By kwb
Replies: 6,459
Views: 1,005,897
Mars was very close to the moon. Q7 and BORG 55FL. Seeing (turbulence) was bad, I took a bunch of pictures (turned out I shot 78) and manually selected the one where Mars looks reasonably round.


Moon and Mars, 2020/09/05 by k kwb, on Flickr
Forum: Pentax Compact Cameras 09-03-2020, 07:35 PM  
Point and Shoot Competition #149 - Things you miss the most
Posted By kwb
Replies: 36
Views: 2,039
Congrats gbl, Bart, Titia and barondla, and thanks Bill for this interesting contest. Looking forward to the next one, gbl!
Forum: Winners' Showcase 09-03-2020, 02:22 PM  
August, 2020 Winner: Timeless
Posted By kwb
Replies: 151
Views: 1,735
I’d like to nominate this.
Forum: Winners' Showcase 09-03-2020, 02:20 PM  
August 2020, Runner-up: Raining Starlight
Posted By kwb
Replies: 52
Views: 532
I’d like to nominate this.
Forum: Pentax KP 09-03-2020, 11:58 AM  
Post Your Best KP Shots
Posted By kwb
Replies: 2,585
Views: 251,373
Meteors aren't from space, look close and you'll see they're from my roof vent, apparently.
KP and Sigma 17-50mm F2.8 lens at 17mm, ISO1600, each 20 sec, 168 frames.

After finding one frame containing a meteor, I blended it back to the stacked photo.
Search took 0.01 seconds | Showing results 1 to 25 of 300

 
Forum Jump


All times are GMT -7. The time now is 02:38 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top