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Forum: Post Your Photos!
11-01-2022, 02:53 PM
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Forum: Pentax SLR Lens Discussion
06-16-2022, 10:11 AM
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If your lens has better resolution than the pixel size of your sensor, adding a teleconverter helps. It magnifies the image.
Otherwise, just tell your ff camera to crop, or crop in post.
Crop and teleconverter give you the same total light, since the latter just takes what would have been the cropped area and spreads the same light over a full frame.
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Forum: Pentax SLR Lens Discussion
06-13-2022, 05:45 PM
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No, you get it back in sensor area.
Either the light is distributed over a small area with low f number or over a large area with higher f number. With the same field of view, the total light is the same.
Here's another way to see it, I have a 0.7 "reducer" that gets me more light because the full frame image captures a wider field of view. It converts my 2350mm f10 mirror lens into a 1650mm f7.
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Forum: Lens Clubs
05-17-2022, 05:35 AM
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Lunar Eclipse. DA* 300mm F4.0 ED with a 1.7 teleconverter, cropped. You can see a little shake in the stars.
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Forum: Pentax SLR Lens Discussion
04-14-2022, 12:17 PM
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I'll second that. The rear gel filters are cheap and work great. (filters on the rear do not need to phase flat over a large region).
And on a long exposure photograph, who needs auto focus? (the Irix is manual focus).
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Forum: General Photography
11-23-2021, 12:54 PM
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Can "At least one" be a choice?
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Forum: Pentax Medium Format
11-02-2021, 03:44 PM
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I love the example, I helped build the main camera for this. We had Texas Instruments make us a few thousand CCD sensors so that we could select 4 of them that had no dead pixels. And we had a pyramid mirror made that sat in the focal plane. The long f number made the edges of the pyramid in focus on the full depth and it split the image into four places for us to reimage onto the 4 CCDs.
This was my first digital camera!.
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Forum: Pentax Medium Format
10-28-2021, 06:42 AM
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1) The total light gathering power? Your 68mm f2 lens on 35mm frame, collects as many photons as your 135mm f4 lens on your 70mm frame.
But for metering, the film is sensitive to photons per unit area, so meter for the actual f number.
2) resolution? The theoretical diffraction limit of the number of spots that can be resolved by an f2 lens on 35 mm frame is the same as that which can be resolved by an f4 lens on 70mm.
But most lenses are not diffraction limited at low f numbers anyway.
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Forum: Pentax Full Frame
04-21-2021, 07:16 PM
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My favorite is the "one inch" sensor, which has a 16mm diagonal!
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Forum: Mini-Challenges, Games, and Photo Stories
02-26-2021, 03:19 PM
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Gold Dust Day Gecko. K1, pentax 28-105mm@105, 1/160s, f6.3
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Forum: Weekly Photo Challenges
02-18-2021, 12:38 PM
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I've chased this elusive creature for a long time, and yesterday it chose to pose on this flower, just in time for this theme.
Pentax k1, iso 800 28-105mm, 105mm, 1/160s, f6.3
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Forum: Lens Clubs
02-05-2021, 01:27 PM
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I have paired it with the SMC Takumar 6x7 600mm F4, 6x7 to K mount adapter.
Also the SMC Pentax 500mm F4.5
It seems to do work fine with these.
But I think your case is different. You are starting with an f8 lens and your 2x converter will make it f16. If the pixels on your camera are about 5 microns, you are already at the diffraction limit. I think that a perfect 2x converter would not give you more resolution on the target. It will give you more dynamic range though, since you can divide the light over more pixels.
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Forum: Pentax Full Frame
09-02-2020, 12:36 PM
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I switched to Full Frame because it is more convenient than carrying around bigger formats.
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Forum: Pentax News and Rumors
09-24-2020, 09:21 PM
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You can go a little further than that. How about pair the SMC Pentax-F 1.7x AF Adapter with the SMC Takumar 6x7 600mm F4, and the 6x7 to K mount adapter?
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Forum: Winners' Showcase
09-09-2020, 08:20 AM
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Forum: Travel, Events, and Groups
08-28-2020, 09:29 AM
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I take a strong interest in this thread. thanks for this.
Early this summer it did a 3 night trip with
K-1 with 24-70 and Iris 15mm and a Manfrotto Pixi Mini Tripod
I put way too much weight in the backpack and suffered for it. I did get some astro photos from the darkest sky I have ever visited though. The mini tripod is fine for astrophotography. I also brought some gel ND filters and did a few water fall shots.
Last week I packed lighter for a 40 mile trip, 4 nights, and a 12000ft. pass.
K-1 with 28-105 (1450 g), a Manfrotto Pixi Mini Tripod and an Iphone camera.
<40 pounds backpack weight including enough food for a sixth day. 1 lb. bivy instead of tent and an ultralight backpack and sleeping bag made by GoLite. You can go through REI web page on packing light to get some ideas.
I haven't yet processed my K-1 photos, but I am very happy with the shots I got from my cell phone camera. I used the tripod to get a few pixel shift photos. I am a big fan of resolution. I also shot some composite panarams with the 28-105, because the expansive views from the top can be captured in 28mm.
I like Deus Ursus sugestions, since my K-1 was not handy I took more cell phone pictures than I would have if the K-1 was in easy reach.
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Forum: Travel, Events, and Groups
08-28-2020, 11:43 AM
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I did miss the Irix 15mm. 28 mm was not short enough for a lot of shots. But the composite panarams do the trick and carrying multiple lenses is a lot of weight.
The bivy is 1 pound, and i have a 2 lb. "two person" tent that I might carry next time.
Here is the pointer to the REI page on lighter backpacking gear.
https://www.rei.com/learn/expert-advice/ultralight-backpacking.html
The other big change I did was to lose 25 pounds of belly fat since spring. That helps a lot.
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Forum: Repairs and Warranty Service
08-23-2020, 04:41 PM
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Thanks for all the advice.
I am a little surprised that some took my post as a flame on Precision, or that I am demanding something of them outside of the norm. I thank you for pointing me to the alternate Precision Terms and Conditions page that I missed when Precision sent me to the first Terms and Conditions page. Had I found the alternate Terms and Conditions before sending this in, I would not have relied on the first Terms and Conditions which said I would be responsible for the cost of return ground shipping only. ($18.95)
I think they should not have conflicting Terms and Conditions pages, but I will go with the repair and move on.
Thanks for helping me think this through,
Teddy
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Forum: Lens Clubs
04-08-2020, 09:01 AM
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K1 attached Celestron 9 1/4 inch f10 lens (2350mm f10). iso400 1/400 second
Here is my moon shot from two days ago. At this focal length, the super moon barely fits on a full frame sensor.
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Forum: Post Your Photos!
09-29-2019, 04:30 PM
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Astrotracer is doing ok in the central field for 60 seconds.
The site is Bortle 3. Elevation 11700ft.
---------- Post added 09-29-19 at 05:31 PM ----------
This site is 11700 ft. elevation, and 1.5 hours drive away. Unfortunately, they will close this road for the winter soon.
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Forum: Pentax SLR Lens Discussion
01-08-2020, 09:19 PM
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Thanks for this. This inspired me to compare my Takumar/Super-Multi-Coated Takumar 500mm F4.5 lens to my Perkin Elmer 600mm solid Cat. I got comparable photos from both. I'm still processing the results, but I found I am pretty happy with the solid Cat, and I'll keep them both.
The Takumar shakes more because it sticks out. The Rear Converter-A 2x-L fits on the Takumar and does a nice job. I'll post tonight's moon photo in the astro pages.
For kicks, I also compared my pentax FA 70-200 and zoomed in post and also tried the 1.7x AF with it. The
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Forum: Welcomes and Introductions
12-30-2019, 09:04 AM
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I got an Irix 11mm! and a camera bag! woohoo!
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Forum: Pentax SLR Lens Discussion
12-26-2019, 09:32 AM
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(standard warnings about difficulty of focus and shake for large aperture long lens apply. These used live view zoom to focus, a tripod, and a timer to wait for oscillations to damp out.)
Shot at f4, 1/200 s ISO100, SMC Takumar 6x7 600mm F4 with adaptor for a Pentax K1.
So far I have only shot it on full frame and I like the results. here is the NCAR building in Boulder from the high school across the way, full frame and crop. I have also shot it with the 1.7 AF adapter. I am looking at getting a Pentax 67 so I can compare the film. It seems such a waste to capture only 24x35 mm out of 60x70 mm (90mm image circle).
cheers,
Teddy
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Forum: Pentax SLR Lens Discussion
12-25-2019, 09:09 AM
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Thank you for this contribution. I've been meaning to do a long lens comparison, but I am still expanding my collection in preparation. I had a 500mm CAT that was messed up and replaced it with a solid CAT. When I get around to it, I also want to compare performance with the AF adapter. I have had some success getting final focus with F4 lenses and the 1.7x AF adapter with good light.
Here is another fundamental question I hope to answer with some experimentation. Under what conditions is the atmosphere itself the limiting factor in resolving detail? When astronomers look straight up through the atmosphere, an aperture larger than 4 inches is likely to have atmospheric distortions blurring the image, unless conditions are really good. So when we look horizontally through the atmosphere, over hot ground, or over a lake, the atmosphere may be giving us a limit.
thanks again for your comparison,
Teddy
SMC Takumar 6x7 600mm F4
SMC Pentax 500mm F4.5
Perkin-Elmer 600mm/f8 Solid Cat
Meyer OPTIK Gorlitz Telemegor 400mm F5.5
Celestron 9.25" edge (2350mm focal length)
SMC Pentax-F 1.7x AF Adapter
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Forum: Mini-Challenges, Games, and Photo Stories
12-14-2019, 07:01 PM
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The morning sun after a very cold snow sticks to "The Flatirons" rock formation over Boulder
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