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Forum: Pentax SLR Lens Discussion
09-05-2021, 04:29 PM
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For star performance, I'd recommend the Pentax-M or Pentax-A 50mm f1.4 or f1.7 (or equivalent film era lenses) over the SMC DA.
I posted sample shots of this exact comparison in the thread linked below:
The Great Astro Lens Test - Astrophotography - PentaxForums.com
I really need a better place to post these comparisons, they seem to be genuinely helpful, but nobody every finds them in this thread haha
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Forum: Pentax SLR Lens Discussion
08-18-2021, 04:18 PM
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The DFA 50mm struggles with aberrations off axis wide open (so the starts will not be points of light in the corners). I've included a review of this lens for astro at the end of my post. the long and the short is that once stopped down to f2.8 it should be looking good, but at that aperture, the M 50mm f1.4 that you already own will be looking just as good. That's the lens I'd be focussing on practising with if I was you.
The 70-200mm f2.8 should work well for astro. I've included another link, showing the coma performance of the Tamron version of this lens. I haven't used this lens, but I've used the second generation Tamron 70-200mm on another mount, and its one of the most impressive lens I've ever used around.
I don't have any info on the 77 f1.8 for astro, but my expectation would be thats its not great. This is based on its coma performance reported on Lenstip, also linked at the end of this post.
Regarding the Sigma 35mm f.4 it definitely works as is on the K1. I think it may have scratched the original K1 body very slightly above the lens mount, but I use a K1ii and I've never even seen a mark at all. In very cold conditions, I wrap a USB powered lens warmer around the 35mm to prevent condensation. I do this on every lens, its not specific to the Sigma 35mm, nor is it something that Pentax WR will prevent.
So once you get the K1ii, go out and practice with Pentax-M 50mm you already own, whilst you decide between the Sigma 35mm or the Samyang 135mm as your astro specific lens purchase (why not both hahaha).
Pentax D FA? 50mm f/1.4 Review - MilkyWayPhotographers.com
Tamron SP 70-200 mm f/2.8 Di VC USD review - Coma, astigmatism and bokeh - LensTip.com
Pentax smc FA 77 mm f/1.8 Limited review - Coma and astigmatism - LensTip.com |
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Forum: Mini-Challenges, Games, and Photo Stories
08-08-2021, 05:08 AM
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I'd always thought these processing challenges sounded like fun, but this is the first time I actually decided to get involved. This is a photo I would have been happy to take myself, so it was a good image to start with.
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Forum: Pentax K-1 & K-1 II
08-03-2021, 12:09 AM
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Its already been explained by mossy rocks and others, but I'll just second that this appears to to be tangential astigmatism of the lens, combined with the effects of using astrotracer on a very wide rectilinear lens. It doesn't appear to be a calibration issue.
I find astrotracer has a sweet spot of focal lengths it is most accurate. Nominally I try to keep the focal lengths from 28mm to 300mm (FF equivalent). If I need a wider field of view, I will stitch together a panorama. I also keep the exposure times to 60 seconds or less. Within this sweet spot I find astrotracer to be super useful. Outside of this range, I use a portable equatorial mount, however they are a million times less convenient to carry to a site, setup, and align, so I'll always prioritize astrotracer if possible.
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Forum: Pentax SLR Lens Discussion
07-24-2021, 03:56 AM
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Thanks for taking the time to shot these and then upload them for us to look at. I love these back to back lens comparison tests.
I enjoyed looking around them at 100% magnification.
To my eye, the M-28 looks a bit better at the wider apertures, but by F8 there is very very little to split them. If anything, at F8 I think the centre of the K-28 is slightly sharper, but at the edges the M-28 is a touch better.
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Forum: Pentax DSLR Discussion
06-27-2021, 02:44 AM
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I picked up a K100D recently. The intention is to utilise it primarily for IR photography, making use of the weak factory IR filter. It was the dustiest DSLR I'd ever seen, but the price was right. Most importantly, the sensor has cleaned up alright and it's got me started with a new type of photography. Its been an enjoying challenge so far, I just need more clear sky days to keep practicing with!
K10D, 18-55 DA-L, 850nm lens filter  |
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Forum: Pentax DSLR Discussion
06-19-2021, 11:31 PM
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Forum: Pentax DSLR Discussion
04-27-2021, 11:00 PM
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Autumn Perseveres
K10D, 18-135mm  |
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Forum: Pentax DSLR Discussion
05-11-2021, 04:55 AM
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Another Tree
K10, 18-135  |
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Forum: Pentax DSLR Discussion
04-29-2021, 09:11 PM
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Thankyou. I spotted the tree behind a construction fence just after sunset. By the time I went to my car and came back and found the best angle, it was close to darkness. I've never shot the K10D at high ISO before, and this was the sharpest of about 10 frames to try and handhold the slow shutter speed still required. Overall then, its one of my worst photos technically, but I really, really like is creatively!
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Forum: Pentax DSLR Discussion
04-02-2021, 09:22 PM
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Path to the Cathedral
K10D, 18-135  |
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Forum: Pentax DSLR Discussion
03-24-2021, 02:54 AM
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Erosion- K10D, 18-135  |
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Forum: Mini-Challenges, Games, and Photo Stories
03-30-2021, 10:47 PM
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I recently came across an older Tamron mirror lens (55BB 500mm F/8) for a great price. My initial reaction was; what can I do with an old, slow, soft, manual focus lens? In its defense, it looked nice and I appreciated the 350 degree focus throw and compact size. I decided, why not double down (literally) and get an equally cheap, era correct 2x teleconverter and shot the moon!
Below is my first effort with my new "$50 moon setup" on a KP body. Overall, its a 1000mm F/16 setup, however the transmission was even slower, more like T20+ in actual use. I tried my hardest earlier this week in my backyard, stacking the best 300 frames out 1150 captured. It was a painstaking process, both in the capture stage and in post, and the results are below.
Ultimately, I don't think the outcome made all the efforts worth it, but it was engaging exercise none-the-less. At the very least, I've learnt a lot about more about lunar imaging that I can apply in the future with better camera/lens setups.
I don't think I quite maxed out the performance of the Tamron mirrror lens, and I'm tempted to try again in the middle of winter with the moon more directly overhead, or without the teleconverter. I'm hesitant though, as the limiting factor will still be the slow capture speed of the Pentax KP (low frame rate, low buffer). I think I'll instead try a landscape image with an interesting moon alignment as the next outing for this lens.
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Forum: Pentax DSLR Discussion
03-25-2021, 05:15 PM
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Thanks blankmampf. The complete lack of scale was the incentive for taking this picture. For references, the field of view covers above 2m of height, but hopefully it would be equally convincing if it was 20cm high, or 20m high!
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Forum: Pentax DSLR Discussion
03-01-2021, 03:27 AM
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Forum: Pentax DSLR Discussion
02-19-2021, 05:37 PM
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K10D, 18-135
One of my worst photos technically, but still a poignant enough scene to warrant posting I feel |
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Forum: Pentax DSLR Discussion
02-19-2021, 11:02 PM
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It looks like other posters have beaten me to it, but I would strongly caution against making any camera choices expecting to use the Samyang/Rokinon 24mm F1.4 anywhere near wide open.
I've purchased two copies previously (ie EF mount) and both were completely unusable below F2.8, due to a combination of field curvature and spherical aberration. In order to match the Sigma 18-35mm F1.8 (shoot wide open) in terms of point shaped stars, they needed to be at F3.5 on one copy, and F4 on the other.
The Sigma 18-35mm F1.8 does have some astigmatism/coma that is noticeable in the edge of the frame, but I confidently shoot it wide open whenever I do landscape astrophotography. I've never felt that way about either of the Samyang lens I've tried, even when stopping down. In addition to the 2 copies of the 24mm, I also tried a 14mm F2.8, and have the 8mm fisheye. Its, always the same story unfortunately.
For reference, my solution to the problem of maximising lens aperture/sensor size is to use the combination of a Sigma 18-35mm with a KP, mounted on a nodal panorama head. A three position pano shot at around 22mm will match the Samyang 24mm F1.4 FoV, with an effective aperture of F1.05.
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Forum: Pentax DSLR Discussion
02-13-2021, 05:28 PM
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Forum: Pentax DSLR Discussion
02-08-2021, 03:18 AM
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Something a bit different this time. An attempt to get the maximum possible detail out of the 10MP sensor, utilising some modern raw conversion techniques that probably weren't available in 2006 when the K10D was released. If anybody wants to pixel peep the full 42MP image, please PM me for a download link. I'm keen for somebody else to zoom in on it 1:1!
K10D, 18-135  |
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Forum: Pentax DSLR Discussion
02-03-2021, 12:48 AM
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Sun Baked- K10, 18-135  |
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Forum: Pentax DSLR Discussion
01-14-2021, 02:34 AM
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Approaching Storm   |
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Forum: Pentax DSLR Discussion
12-02-2020, 03:44 AM
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One interior shot, and one exterior shot:  
K10D. 18-135mm. |
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Forum: Pentax DSLR Discussion
01-18-2021, 02:48 AM
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Forum: Pentax DSLR Discussion
01-27-2021, 04:19 AM
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18-135mm, K10D   |
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Forum: Pentax DSLR Discussion
01-18-2021, 07:21 PM
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Thank you!
It was an extremely high dynamic range scene. I knew the K10D wouldn't be able to capture it all, so I let the sky clip and had my first attempt at black and white post processing the rest of the data.
I might be working around its limitations, but I'm glad the K10D lead me to a new approach. Thats the reason I have been using it recently.
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