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Forum: Troubleshooting and Beginner Help 08-04-2021, 03:00 PM  
Looking for tips on intervalometer settings
Posted By jon.partsch
Replies: 12
Views: 530
I have found that an additional 2 seconds is plenty adequate for writing RAW+Jpeg to card on my K1ii, so that would be a 17 second interval for a 15 second exposure.



That is an excellent suggestion!
Forum: Troubleshooting and Beginner Help 08-04-2021, 01:35 PM  
Looking for tips on intervalometer settings
Posted By jon.partsch
Replies: 12
Views: 530
If you are getting 600 exposures at 15 seconds each on a full battery, that means the sensor is exposed to the sky for 600 x 15 = 9,000 seconds, or 150 minutes, or 2 and a half hours. It makes no difference how the exposures are spaced out during the night, you have 150 minutes to catch a meteor any way you space it out. You are MUCH better off taking all your 600 shots back rather than spacing them out, but you need to do these things:

1. Go to Meteor Shower Calendar 2021-2022 - American Meteor Society and find when the meteor showers are occurring that will be visible at your location. Right now, you may be able to catch some of the Alpha Capricornids and the Perseids (one of the best showers of the year) is ramping up now, and will peak on Aug. 11th.

2. Aim your camera so that the radiant of the meteor shower will pass through the image frame during the 2.5 hours or so that your battery will last (you can also re-aim your camera part way through if you need to). I would think you would be virtually guaranteed to get some good shots this way.
Forum: Troubleshooting and Beginner Help 08-04-2021, 11:49 AM  
Looking for tips on intervalometer settings
Posted By jon.partsch
Replies: 12
Views: 530
My suggestions would be to:

1. get an external battery or grip with second battery
2. set your intervalometer to only take 600 shots, because that's all your battery can accommodate
3. The only way I can think of to get more shots out of the battery you have is to turn off any functions that are not needed, such as autofocus, image preview after the shot, SR, slow speed noise reduction (use dark frames in post later), etc.

I don't see any advantage to "spreading out the shooting more" as you will still be limited by the battery, except for a possible slight reduction in noise by allowing the sensor to cool off a bit between shots.
Forum: Pentax SLR Lens Discussion 08-04-2021, 10:17 AM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
Well, replacement lens #1 ... we'll call it lens #5 ... arrived yesterday, and the infinity focus is way off on this one too. Lenses #6 and #7 should arrive tomorrow and night skies should be clear for the next several days for testing.
Forum: Pentax SLR Lens Discussion 08-03-2021, 05:01 PM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
Sorry, I did not mean to respond as if you were suggesting that I buy the 15-30mm. I was just offering my thoughts on it, since you mentioned it. I think if I wasn't interested in astro, then the 15-30mm would be a logical choice, but as soon as I got and used the Sigma Art 35mm f/1.4, my focus shifted to primes. For me, wide angles below 35mm will be primary used for astrophotography and landscapes, where care is taken to set up the shot carefully, so a zoom isn't necessary, though I'm sure it's a better choice for many.

Oh I also just got the old SMC Pentax-FA J 18-35mm f/4-5.6. It came with a *ist D parts body I purchased. That should be fun for comparison LOL
Forum: Pentax SLR Lens Discussion 08-03-2021, 09:34 AM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
Yes, well, the Pentax 15-30mm is $1300 USD and the Samyang 14mm is $250 USD or so, so the hassle of obtaining and testing multiple copies is worth it. Plus, I assume a good copy will perform better than the Pentax 15-30mm does at 15mm due to being a prime. I see little utility in a ultra-ride angle zoom. Any ultra-wide shot I am doing will probably be a considered and deliberate set-up, so the convenience of a zoom is probably not needed. Zooms seem much more useful in the middle focal lengths and long focal lengths where you are working with dynamic subjects like human models and wildlife. I had a huge desire to get the Pentax 15-30mm for a while, but I think my 14mm, 24mm and 35mm primes will be even better, and for just slightly less money.
Forum: Pentax SLR Lens Discussion 08-03-2021, 07:39 AM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
Absolutely, even with (and maybe especially with) a $2000 USD new Pentax lens. I have a historic brick building just down the street, and my office building (should I ever return there post-COVID) is a concrete monolith with fluted or grooved patterns in the outside walls - both provide great detailed texture for testing. I am finding shooting the night sky stars to be a great torture test for these wide angle lenses because certain flaws show up with points of light that may not be visible shooting a brick wall.
Forum: Pentax SLR Lens Discussion 08-02-2021, 04:58 PM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
If I was at all confident in opening the lens up to correct de-centering, I would have loved to try and correct the issue with lens #1 that I described above. That thing was spectacularly sharp in the center of the frame!



I don't do any shooting that would cause me to be tempted to get the 85mm. I am interested in the 135mm f/2.0 however. I am using the 14mm with my K1 mark ii, but I also plan to use it on my K-01 for astrophotography as that one is "full spectrum", and I can add a filter to allow H-alpha and sodium-2 discharge spectrum will blocking most infra-red.

I was almost tempted to keep lens #1 and see if I could send it for warranty service to hopefully correct the extreme coma while retaining the amazing sharpness, but I had read your story or one like it before, and I figured they would just tell me it was already within spec.

Hopefully there will be a winner in the next batch of three lenses that are on the way!

Testing these lenses, I am finding precise focus much more difficult, especially against night sky stars, than with the 24mm f/1.4. Best practice, I think, will be to pre-focus to infinity before the sun goes down, and tape the focus ring in place. That way I can also quickly cycle through the lenses to ensure the stars don't move much between tests. I find it very helpful to have the same stars in the corners of the image for comparison between lenses.

I took shots at ISO 1600 and 4 seconds for the f/2.8 aperture and 8 seconds for the f/4.0 aperture. This ensured very sharp stars even without any tracking.
Forum: Pentax SLR Lens Discussion 08-02-2021, 01:14 PM  
Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses
Posted By jon.partsch
Replies: 12
Views: 905
Folks,

Understanding the highly variable quality (sample variation) of the Samyang/Bower/Rokinon lenses, I recently purchased two copies of the 24mm f/1.4 (a Bower and a Samyang). I was pleased to test them and discover that they both performed very well! Infinity focus was correct, and resolution was great, distortions/aberrations minimal. I sent the Bower back due to slightly higher coma in one corner.

I then purchased 4 copies of the Samyang 14mm f/2.8, and was appalled to discover major flaws with all of them. All four of them didn't focus to infinity. Lend #1 and #2 were off by at least 1/2 inch turn of the focusing ring. I adjusted all of them, which is easy to do with tutorials in various forums and on YouTube. I then took them out to my favorite semi-dark sky location to test them. Aimed at the zenith, Vega was in just about the middle of the frame. I was further frustrated upon opening my raw images in Lightroom to discover additional flaws. Having the constellation Lyra in the center of the frame was great because it also gave me the visual double Epsilon Lyrae to work with along with the super-bright star Vega. I tested all the lenses at f/2.8 and f/1.4.

Lens #1 was astonishingly sharp in the center! Epsilon Lyrae was clearly resolved as two distinct points of light and Vega as a very small round white dot with no color fringing. There was virtually no difference between f/2.8 and f/4.0. Oh, if only performance across the frame was so good!!! I assume one of the elements controlling coma correction was de-centered as the coma distortion was extreme on the left hand side, rendering stars as thin lines pointing toward the center of the image - coma was also terrible here at f/4.0. As I look at the coma distortion all the way around the edges of the image, the lines of light do not point to the center of the image, but to a point about 2/3 of the way across the image in the area of the middle-right side of the image. Coma on the right side of the image was significantly better, and what I would call acceptable.

Lens #2 had about 3/4" of free play in the focusing ring. The action was dampened, but change in focus was not actually engaged until the ring is turned about 3/4". Turn the ring back the other way, and it has to move about 3/4" again for the plane of focus to actually start changing. I thought perhaps I had not tightened the set screws on the focus ring enough when I adjusted the infinity focus point, so I tightened them and tried focusing again the next day, but the free play in the focus was not improved. This lens is not usable.

Lens #3 had optical de-centering - the left side was completely out of focus at both f/2.8 and f/4.0

Lens #4 was the best all-around performer (across the frame), but it was worse in the center than #1 and #3 (#2 couldn't be evaluated due to the play in the focus ring). Vega wasn't as sharp and Epsilon Lyrae was barely resolved as two points of light. In addition, there was hazy color fringing on the left side of stars (not green, magenta, or purple, but instead the expected color of the star e.g. blue for Vega). I don't know what kind of distortion or issue this is, but it was also somewhat evident on lens #3.

Anyway, I am keeping lens #4 for the time being and sending the other three back for replacement, so I will receive three more copies to test. I am hoping to be able to improve upon lens #4.
Forum: Pentax News and Rumors 07-15-2021, 04:59 PM  
Giveaway: HD Pentax-FA 31/43/77mm | Enter here once per day until July 31st
Posted By jon.partsch
Replies: 2,870
Views: 64,885
One more for me please!
Forum: Welcomes and Introductions 07-15-2021, 04:58 PM  
Pentax nut returns to photography
Posted By jon.partsch
Replies: 20
Views: 823
Welcome to the forums!
Forum: Welcomes and Introductions 07-15-2021, 04:56 PM  
Hello~
Posted By jon.partsch
Replies: 13
Views: 366
Welcome to the forums!
Forum: Troubleshooting and Beginner Help 07-15-2021, 02:44 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
This would be awesome! It's always best to avoid complete disassembly of the aperture assembly if possible, as long as it can be soaked (flush cleaning with the aperture in place has never worked for me for long ... oil always comes back). That said, I have completely disassembled and cleaned aperture assemblies, and *still" had the oil come back because it migrates in from the focusing helicoid. This is why I always recommend a complete teardown, cleaning and re-lubrication, if possible.

For "soak" cleaning of parts a cheap ultrasonic "jewelry" cleaner is a very useful tool. Like this: amazon.com: Magnasonic Professional Ultrasonic Jewelry Cleaner with Digital Timer for Eyeglasses, Rings, Coins (MGUC500): Industrial & Scientific?tag=pentaxforums-20&

If possible, if the part is small enough, I prefer to use a small 4-oz size Mason jar with solvent and place this in the ultrasonic cleaner filled with water, rather than put the solvent in the ultrasonic cleaner directly.

Also, I find Zippo/Ronsinol lighter fluid or Colman fuel works better than mineral spirits, but odorless mineral spirits would certainly be friendlier to work with. My guess is that mineral spirits would work better than isopropal alcohol.
Forum: Troubleshooting and Beginner Help 07-15-2021, 09:25 AM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
I'll say this again for clarity:

Coleman White Gas (aka camping fuel) or Zippo/Ronsinol lighter fluid (NOT Butane) is the long sanding gold standard for cleaning and servicing lenses and shutter assemblies. This is not new information, and it is what the professionals use. Full disassembly and cleaning/replacing of *all* lubricants in vintage manual focus lenses is advised if at all possible as "oily aperture syndrome" can quickly reappear due to old, deteriorating lubricants migrating in from the focusing helicoid.

Don't use isopropal alcohol - it's much less effective and more trouble than it's worth. It is good only for light cleaning.

Don't use acetone, MEK or any other solvent unless you have a *specific reason* for doing so. And, if you do, be aware that you are risking damage to paint or any plastic components in the lens and are exposing yourself to a significantly greater health hazard.
Forum: Troubleshooting and Beginner Help 07-14-2021, 07:09 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
Yes! a total dust and crud magnet! so much so that I doubt it would shed any dust into what I am working on, if only it was grippy enough to actually remove any lens rings! Mine is chinese, light gray, apparently made of silicone, and purchased on AliExpress. Perhaps it is a cheap knockoff of a better set that was the same light gray color, but I don't know.
Forum: Troubleshooting and Beginner Help 07-14-2021, 06:04 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
Your attitude is not called for. I have rebuilt Vivitar lenses and never run into any kind of thread-locker or glue requiring MEK to dissolve. As I'm sure you know, Vivitar lenses were produced by several manufacturers, and were sometimes simply re-badged version of other lenses. I can accept that a few lenses may have used some special threadlocker, but that hardly calls for use of MEK on just any old lens. It's total overkill, and it's a highly hazardous substance. Do you have any evidence that it is required for the lens in question by the OP? If not, then it's a totally inappropriate solvent.
Forum: Pentax News and Rumors 07-14-2021, 04:54 PM  
Giveaway: HD Pentax-FA 31/43/77mm | Enter here once per day until July 31st
Posted By jon.partsch
Replies: 2,870
Views: 64,885
One more for me, please!
Forum: Welcomes and Introductions 07-14-2021, 04:54 PM  
Hello to all Pentax lovers
Posted By jon.partsch
Replies: 22
Views: 713
Hello, and welcome to the forums!
Forum: Post Your Photos! 07-14-2021, 04:52 PM  
Nature trying a new area ...
Posted By jon.partsch
Replies: 7
Views: 256
NIce heron shot!
Forum: Troubleshooting and Beginner Help 07-14-2021, 04:51 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
I find it highly improbable that MEK is the "only" way to service a Vivitar Lens, and I find it highly improbable that it is even the best way, regardless of what these "rebuild guides" say to which you refer.
Forum: Troubleshooting and Beginner Help 07-14-2021, 08:32 AM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
It really looks like the same set I have, but perhaps not. My set has been completely useless so far.

---------- Post added 07-14-21 at 08:47 AM ----------







Zippo lighter fluid (or Ronsinol) works great, but Coleman "white gas" camping (lantern/stove) fuel works just as well and is way cheaper if you are going to be doing this kind of thing often.

Acetone also work great, but is total overkill for this, and you risk stripping the paint or melting any plastic parts - acetone is the solvent of choice for removing really difficult adhesive on camera leatherette.

MEK (Methyl Ethyl Ketone) is extremely hazardous and I urge you to stay away from it at all costs. It should not be sold to sold consumers IMHO. I spent 16 years in the hazardous materials cleanup industry, and had to know all about the toxic effects of chemicals like this for my job. Use Acetone with care only if lighter fluid or white gas wont work for you, but even Acetone should not be needed for this kind of work.

Isopropal alcohol has very limited utility in camera service and repair. It can be used for a light cleaning of outside surfaces of things, or for lens elements prior to reassembly, but I use Coleman fuel for almost all of this kind of thing now as it works better and is more multi-purpose.

Everything I have said above has been told to me by highly respected classic camera restoration experts, and verified by me personally in a couple dozen complete lens and camera teardowns and restorations.
Forum: Troubleshooting and Beginner Help 07-12-2021, 08:57 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
I have this set of lens ring cups and find it completely useless - it's silicone, and it's too slippery to get traction on a ring that I can't otherwise just remove with my fingers. I think you will find you need a "grippier" type of material.
Forum: Pentax News and Rumors 07-12-2021, 03:45 PM  
Giveaway: HD Pentax-FA 31/43/77mm | Enter here once per day until July 31st
Posted By jon.partsch
Replies: 2,870
Views: 64,885
One more for me please!
Forum: Troubleshooting and Beginner Help 07-12-2021, 02:02 PM  
lens disassembly help
Posted By jon.partsch
Replies: 26
Views: 1,004
Hello and welcome to the forums!

I doubt you will find specific instructions for this lens, as I doubt it is a "classic" that many folks would be interested in using the time and effort to repair. Do you have experience with lens disassembly and service? Do you have the proper tools?

I will say that it should be a simple lens design and with some practice reconditioning lenses, you should be able to make the repair fairly easily.

I realize what I said above may note really help, but you can look on youtube for lens repair videos to see, in general, how old manual focus lenses are put together and what to expect when disassembling one.

I will caution you that the "partial disassembly and flush with lighter fluid" approach for dealing with oily apertures has never worked for me - the oil always comes back shortly. The only relaiable approach in my experience is a complete tear-down, cleaning, re-lubrication, and re-assembly.
Forum: Pentax SLR Lens Discussion 07-12-2021, 01:21 PM  
Help with testing Bower / Samyang 24mm f/1.4 lens
Posted By jon.partsch
Replies: 8
Views: 543
What is the reason for such condescension and semantic nit-picking? Did you get up on the wrong side of bed today? You should consider whether you have something positive and constructive to say before you post.
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