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Forum: Monthly Photo Contests
04-05-2022, 06:15 AM
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I would like to nominate this photo
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Forum: Troubleshooting and Beginner Help
09-14-2021, 03:26 AM
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Yeah, no problem with other “A” lenses, including a Rokinon 50mm 1.4, so it’s the lens alright. :mad:
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Forum: Troubleshooting and Beginner Help
09-13-2021, 05:13 PM
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I obtained my DA-300 already converted to screw drive, and quite frankly if someone offered to fix the SDM for free, I wouldn’t bother.
Convert to screw drive, and don’t look back…
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Forum: Troubleshooting and Beginner Help
09-13-2021, 05:08 PM
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Update:
Obtained a second Samyang 14mm/F2.8 - it has the same problem… aperture pin sticks up too far, won’t mount when aperture ring set to “A”… must be a defect affecting a batch of them presumably…
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Forum: Troubleshooting and Beginner Help
09-07-2021, 10:29 AM
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Good diagnosis! Thanks!
The “A” pin on the 14mm seems to be sticking up a bit far (or it’s the wrong shape). Instead of sticking up like a ball bearing that’s slightly proud of the lens mount surface, it sticks up more like a cylinder with a rounded head. So, it ‘hard’ catches on the screw drive hole, and doesn’t retract when turning the lens as it should.
My Rokinon 50mm (same brand, different name) is fine in comparison, and the pin looks and works as expected.
Maybe they left out a washer or similar behind the pin on the 14mm?
I imagine they’d correct the problem under warranty, but I might just live with it…
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Forum: Troubleshooting and Beginner Help
09-07-2021, 04:34 AM
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Strange problem... picked up a Samyang 14mm (new) a couple of months ago, but only just tried it. This is a manual focus lens, but has an 'A' auto aperture setting, as well as manual aperture F2.8-F22.
When mounting the lens, on both a K3 and a K1 mk II, if the aperture setting on the lens is set to "A" when mounting the lens it stops hard about 1/2 way through the rotation, before it locks into place. With the aperture on the lens set to any other setting, it mounts completely normally. I've looked at it and don't see anything obviously wrong. If I set the aperture to 'A' *after* mounting the lens, it seems to work fine, and it can be removed normally.
Anyone else with this lens have this problem, or seen it with any lens?
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Forum: Sold Items
01-18-2020, 07:42 AM
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Forum: Pentax Medium Format
01-17-2020, 05:19 AM
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Thanks for the info. I’m hoping to use this lens mostly for rocket launches, both here in VA (yes, we have rockets to the ISS!) and FL, where distance to rocket is on the order of 2-10 miles depending. Focusing shouldn’t really be an issue at that distance hopefully, and auto exposure, (which is not available with this lens of course using a K body) may not be that helpful anyway as when the rocket lights the exposure changes dramatically, so probably best to pre-guess exposure. Hours of waiting followed by 30 secs of frantic panic kinda sums it all up!
Lens coming from Japan, looks to be about as mint as can be, doesn’t even have scratches on the bottom of the tripod foot(!) and has both regular and polarizer filter holders, plus filters, caps, case, etc.
Meantime, here’s a few of the Antares Cygnus 12 leaving VA for the ISS from November, 300mm DA*: I’m sure they could be processed better... :) Distance about 2 miles, which is as close as you can be. Mirage was a problem, even though it was pretty cold.
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Forum: Pentax Medium Format
01-15-2020, 04:58 PM
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Thanks for going to the trouble and posting those.
I just picked up a good 645 1.4x for $50 from Japan and will probably get a 645 2x if only to ‘have the set’ :) Both seem dirt cheap on eBay considering the size of the glass elements and the bomb proof construction. Mechanically speaking the coupling between 645 components seems stronger than the K mount coupling.
BTW, if you don’t mind, what is the length of the tripod foot on the 645 600, and what is the size of the tripod threads (lens not here yet...need to get a plate for it), in pics it looks like 3/8 with a 1/4 insert reducer, or maybe it’s straight 1/4?
Thanks!
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Forum: Pentax SLR Lens Discussion
01-09-2020, 04:22 PM
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Indeed, keeps it simple and no need for a hyper expensive image degrading optical solution.
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Forum: Pentax SLR Lens Discussion
01-09-2020, 09:01 AM
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Mirror lenses are quite similar to some astronomical telescopes, namely Schmidt Cassegrains, and Maksutovs.
The first ‘problem’ they have is they are quite obstructed. The central obstruction is maybe 35-40%, and causes a reduction in contrast.
The second problem is that their aperture to focal length ratio is usually quite high, as in F8 or worse, which makes focusing difficult, and results in longer exposure times, which can be problematic due to long focal length (ie vibration/shake). The aperture is also fixed.
The third problem is that for economy of manufacture, the mirrors are made with a spherical figure, rather than parabolic, which leads to spherical abberations. The front glass element is supposed to correct for that, but...with varying success.
Lastly, in camera lens configuration there are additional lenses in the construction that don’t appear in telescopes at all, to make the image is right side up and correct left to right as well, and hopefully bringing the image to focus over the entire area of the film or image sensor (flat field).
As an aside, a photographic Schmidt cassegrain telescope known as a Schmidt camera had an image plane so curved that the film (back in the day) had to be fitted to a curved film holder in order that the entire image be in focus.
At the end of the day, mirror lenses are a compromise in many ways, and the price is generally very low, so you know something has to give. I would expect the takumar to be superior in almost every way, though it will be prone to chromatic aberration (color fringing) due to the age of its design and no ED elements, and it’s length makes it susceptible to vibration/shake unless well supported.
Just my $0.02...
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Forum: Pentax SLR Lens Discussion
01-07-2020, 05:08 AM
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There is no diagram of that lens in the reviews.
It’s difficult to tell. I have a cemented pair with fog that is balsam separation, looks almost like ‘crystals’ between the elements’ but from a distance it looks like whitish fog.
Did the front element come out by itself, or did you find two pieces of glass mounted in a metal ‘cell’?
If 2 elements mounted together in a cell, it’s difficult to tell if they are cemented without disassembly. It is highly likely that the cell has a drop or two of lacquer on the threads that holds the top ring of the cell in place. You can use nail polish remover (acetone) to dissolve the lacquer and remove the ring, allowing the elements to be taken out of the cell, at which point you will know if they are cemented or not. I stand the cell on its side, and using a hyperdermic syringe and needle, run a little acetone around the edge and leave it for a few minutes before trying to unscrew the ring.
I got a set of rubber/silicone tools from amazon that allow you to remove rings in lenses and cells using friction (once the lacquer is dissolved). It it possible to use a lens wrench too, but be careful as the metal tool can scratch glass if you slip.
If there are two loose elements, make sure you know the order and direction (up/down) they were in. If possible, keep them together and make a mark with a pencil across the edges of both so you can put them back exactly as they were.
I would use some rubbing alcohol or even acetone to clean the glass and a microfiber cloth. Reassemble. Done.
If they are cemented, it’s more of a problem...
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Forum: Pentax Forums Giveaways
01-06-2020, 09:45 PM
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Forum: Pentax SLR Lens Discussion
01-06-2020, 06:49 PM
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The crack is actually in the second element, which I think is ED glass if the diagram in the forum lens reviews section is correct.
Judging by the state of the ring that holds the front element in place (and the others inside the lens), I would say there has been no attempt to take it apart since it was made (lens spanners / wrenches generally leave a mark in the soft aluminum rings, knock the flat black paint off etc, no sign of that at all). Unless someone had a replacement element, I’m not sure it would be at all advisable to take it apart, it could only make things worse.
It may have been ok as is, the aperture blades might have been an easy fix, but I decided not to take a chance on it, and sent it back today.
As has been pointed out, it could have got worse if the glass moved at all, fixing it properly (assuming Pentax even have the damaged element, they may not) would have been really expensive I’m sure, and would have exceeded the used value of a similar lens. That said, it might have been just fine ‘as-is’ for the next 20 years...and the crack may have minimal to zero effect on images, it is maybe 5-8mm from the edge.
At a massive discount to a few hundred bucks, it might have been worth the risk, but I decided not to even ask them if they’d consider it.
Anyone who’s interested in making them an offer (I don’t know what they’d be open to) could contact Josh at Calagaz Photo in Pensacola, FL, you might get lucky, I have no idea, but I can’t imagine what else they’d do with the thing in its current state. It’s missing it’s rear filter, but I imagine any 49mm UV or clear filter would fit the holder, which is present.
I would also say I don’t think Calagaz really knew. Unless you’re looking closely, or with a flashlight, the crack is not super apparent (but they should have seen it). Likewise, the aperture stickiness could have been missed if you just operated it once or twice, it’s a bit sporadic, but it is a problem they should have seen. They sent me a return label right away.
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Forum: Pentax Medium Format
01-05-2020, 11:17 PM
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When using a 645 lens on K mount (say the 600mm ED IF f5.6) using the Pentax 645->K adapter, which would work better on an apsc camera (K3 or K5):
a) the 645 version 1.4 teleconverter mounted to the lens, before the K adapter?
Or
b) the well regarded, (almost magical... ) 35mm (K mount) 1.4x-l converter mounted after the K adapter?
Anyone tried (b)? I can’t think why it wouldn’t work... ;)
I suppose if mechanics are a consideration, perhaps the mechanical connection between 645 lens and 645 converter might be stronger(?)
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Forum: Pentax SLR Lens Discussion
01-05-2020, 02:46 PM
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Agreed on all points! At this point I’m 99% on sending back and forgetting about it, lest it become another box in the basement...
SCT’s - that’s an idea. I have an 8” Celestron in a gps/computerized fork mount, so I know the ins and outs. I suppose a small (relatively) refractor might be a possibility too, though I’ve never used one for terrestrial, but APOs tend to be up there in price, and achromats are the definition of CA. I’ve bought from High Point before.
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Forum: Pentax SLR Lens Discussion
01-05-2020, 02:38 PM
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Haven’t seen one used recently, but will certainly keep an eye out!
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Forum: Pentax SLR Lens Discussion
01-05-2020, 11:10 AM
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Forum: Pentax SLR Lens Discussion
01-05-2020, 08:30 AM
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Yes, looked for a A* 600. Saw one for a split second on that auction site, then it disappeared, now shows as completed / sold. It’s possible it didn’t actually sell, may contact seller and see.
$2700 for the current DA 560 would be a deal!
Patience is key... :)
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Forum: Pentax SLR Lens Discussion
01-05-2020, 08:13 AM
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Actually, that is an excellent point I hadn’t really considered, and 100% on target.
Out of interest, have you ever tried the 645 600 on a K mount camera? Stop down metering is a given, but they seem reasonably available in good/excellent shape compared to older 35mm lenses from the same era... reviews on here seem very good.
I recently gave my 645 film body and lenses to my niece for a university project, but kept the Pentax 645 -> K mount adapter...
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Forum: Pentax SLR Lens Discussion
01-05-2020, 08:04 AM
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Thanks for the sanity check!
Yes, it’s a lot of money for a lens with a crack. Seller and I didn’t know it was cracked though, so price paid was ostensibly for an uncracked one!
Not sure there’s any amount of $ partial refund that would convince me to keep it, as it could just turn into a paperweight at some point, assuming it isn’t now... That really was the decision at this point, but crazy to keep it at any price I think....
No idea how the crack occurred, only the original owner knows that for sure (bought from a dealer). No obvious hit on it, this thing weighs about 15lbs and is a little over a foot long, so I’m not sure a drop would even leave a mark.
Going to box it up, ship it back...
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Forum: Pentax SLR Lens Discussion
01-05-2020, 06:16 AM
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Just scored a 400mm F2.8, with a 1.7 AF teleconverter for what seemed to be a good price... described as ‘excellent’.
Lens arrived, had a real tree camo sticky backed vinyl covering, which I removed, revealing very nice condition white exterior, a few marks, but nice. Filter holder is there, has no filter, but could easily fit one, I think it may require one in place.
Aperture blades, which are accessible from the back, are sticky. Maybe some alcohol would fix, or send to KEH.
Glass is clear, focusing is reasonably smooth. Have not attempted to take a pic with it yet.
The BAD part....
There is a CRACK in the second element. It is basically a straight line crack about 1cm or so from the edge of the second element. Difficult to see at first glance, but it is there (and now that I see it, I can see it in the seller’s somewhat out of focus photo too). I guess they didn’t notice it.
Seller's pic attached, the crack is at 3-4 O'clock. Yeah, obvious now.... :)
I spoke to the seller yesterday, and I have a return label, so can get $$$ back on this ($2600) they seem reasonable at this point.
But... should I run like hell, send it back, cry for a bit and forget about it.
Or make some ridiculously low offer to just keep it?
It’s possible the crack could have little to no effect. It’s possible it might never move. It’s close to the edge of the lens, perhaps it doesn’t even intrude into the APSC field of view??? I know sigma say one of their lenses (bigma maybe) takes a 95mm filter, but you can use a step down ring to 86mm when shooting APSC, which got me thinking....
My use for this lens is for shooting rocket launches using my K3, which may be at a range of 2 miles to 10 miles distant. The attraction of this lens was that with the 1.7 AF tc I could get to equivalent of a 1020mm f4.7 approx, still have some autofocus ability, it would also work with the 1.4x-l and 2x-l converters, which are rated about as good as it gets for TCs, albeit manual focus.
Alternatively, get a Bigma 50-500, or even a Pentax 150-450, pocket the change and never look back. The DA 560 is too much $$$ for me I think.
I do have a DA*300 that I could put a 1.4 TC on and save a fortune. Not quite the same but...
I don’t really want to have a ‘stupidest thing I ever did’ story (either way!).
Thoughts?
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Forum: Sold Items
12-25-2019, 04:50 AM
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Forum: Visitors' Center
10-15-2019, 10:50 PM
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Had the same problem with my ist*D with a new set of lithium AAs. The fix was to put the AAs in a flash, charge it up, fire once, and then put the batteries back in the camera, after which it worked fine from then on. Not sure if this is a fault with the camera or what exactly, but it seems it doesn’t draw enough power to ‘wake up’ the new lithiums initially. If you don’t have a flash, any device that draws a bit of power should do the trick (assuming the problem you are having is the same). Wierd...
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