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Forum: Pentax SLR Lens Discussion 5 Hours Ago  
Does an M42 adapter work with all M42 lenses?
Posted By marcusBMG
Replies: 23
Views: 312
Forum: Digital Processing, Software, and Printing 5 Days Ago  
FastStone Image Viewer and extracting Jpg's from RAW DNG's
Posted By marcusBMG
Replies: 32
Views: 945
To edit the full sized RAW in Faststone, first press "A" letter key. You will see the full sized RAW file load.
Forum: Lens Clubs 5 Days Ago  
DSLR fun with 28mm: Club for any 28mm lens
Posted By marcusBMG
Replies: 810
Views: 119,602
---------- Post added 21st Mar 2019 at 14:07 ----------



Great pics gifthorse. What apertures were those at?
Forum: Lens Clubs 6 Days Ago  
DSLR fun with 28mm: Club for any 28mm lens
Posted By marcusBMG
Replies: 810
Views: 119,602
I spotted this and noted the PKA mount - perhaps not quite as rare as hens teeeth but certainly not easy to find. So I bid a reasonable amount. Now the comparison with the viv (tokina) 28mm f1.9 I already have. will be interesting.
From the pics so far, I can say that this lens looks better than the 28mm f1.9 wide open: less aberrations specifically, both are already pretty sharp in the centre but fall off away from the image centre, even on apsc.

I was particularly impressed with the beach sign, very little fringing and contrast good even at f2. I took shots of the castle at the range of apertures, only at f8, f11 did the edges really sharpen up to close to the centre.
Forum: Pentax SLR Lens Discussion 03-19-2019, 12:54 PM  
Recommendation for affordable 750mm+ birding lens please, thanks
Posted By marcusBMG
Replies: 43
Views: 1,336
No No No don't even bother with that chinese made c**p - various cheap mirrors, t-mount 480-800mm "zooms". 800-1300mm "zooms", old style t-mount lenses like the one in the previous post..
Forum: Pentax SLR Lens Discussion 03-19-2019, 10:20 AM  
Recommendation for affordable 750mm+ birding lens please, thanks
Posted By marcusBMG
Replies: 43
Views: 1,336
The farther away you want to peer, the more vastly expensive it becomes to get best results.

I too would suggest for relatively distant birding etc that the "digiscoping" options are the ones that will give you reach beyond your good sigma 50-500mm without necessarily breaking the bank. Then the question becomes which scope? Answer: the best you can afford! My middle of the road opticron HR66-GA (old model) basically isn't good enough, I have not been impressed with the results from my digiscoping attempts with that. My impresson is that small sensor photographic devices are the way to go - your smart phone, or perhaps something like a Q. As the sensor size increases you are spreading that exit pupil cone of light vastly thinner.. (talking about eyepiece projection which is the most common mode).
The scope manufacturers usually offer hopelesly overpriced digiscoping adapters but something like this which I picked up for a fiver off ebay, is readily adapted.
An alternative would be to look at acquiring a primarily astro telescope eg st like a celestron 8", to set up in your ?conservatory and adapt for land photography.

addendum if you check the review listings for the tamron adaptall 500mm mirrors I have put in links to video reviews, one in particular discusses using these with tc's, with some v good results.
Forum: Pentax SLR Lens Discussion 03-19-2019, 07:35 AM  
Is this the rarest K-Mount lens? (Sigma 800mm f5.6)
Posted By marcusBMG
Replies: 7
Views: 835
The first mention of a 800mm apo is from 1991 on the sigma history page.This lens is from 1999 apparently, and is only listed as Nikon, Canon, Sigma mounts. Definitely requires mount clarification. Of itself I wouldn't pay anywhere near asking price for well used lens like this, BUT if it is pentax HSM (history spec page does say HSM) then rarity changes that.

Sigma 800mm F5.6 APO EX Launched June 1999 - Sigma Imaging (UK) Ltd

I can suggest the rarest is the 1000mm f8 from 1991 see this scan.
Forum: Pentax Film SLR Discussion 03-17-2019, 03:11 PM  
Crazy test, recoating front element with wear glasses technologies
Posted By marcusBMG
Replies: 3
Views: 510
I have tried polishing the hazed rear elements of the 400mm f6.3's using a neigbours polishing wheel and rouge (he worked in the optical industry). The IQ after cleaning was sub par, so basically it didn't work.
Forum: Pentax SLR Lens Discussion 03-17-2019, 01:41 PM  
WD40 safe for stiff focus?
Posted By marcusBMG
Replies: 13
Views: 1,970
+ 1 for prev comments. The only lubricant I use on lenses (I mean other than good grease for relubing a helicoid) is tiny amounts of fine oil from a precision oiler/oiling pen. Very good for eg filter threads, easing a sticky aperture ring.
Forum: Lens Clubs 03-15-2019, 10:15 AM  
Adaptall Mount Club (Tamron).
Posted By marcusBMG
Replies: 3,663
Views: 611,578
I came across a couple of good U-tube reviews of the 500mm mirrors:
















You Tube



















You Tube




Both are also good on technique.
Forum: Lens Clubs 03-10-2019, 10:44 AM  
The Mirror Lens Club!
Posted By marcusBMG
Replies: 992
Views: 372,534
Yep looks good.
Forum: Lens Clubs 03-10-2019, 07:27 AM  
300mm plus Lens Club: discuss your long lenses
Posted By marcusBMG
Replies: 30,831
Views: 2,808,516
Well you've upped the asa and got a 1/500 shutter but the bottom line is the light is dull dull dull, that shutter speed is still not that fast, more than susceptible to vibration and shake affecting the end result, and your shot is still a stop under exposed, as per the histogram (faststone, fyi). While it would be useful to get the RAW into eg LR and see what the max is that can be extracted from the pic (the default jpg is going to reflect the dull light and underexposure), even a quality lens can only do so much when the llght is poor. You can't really conclude much from comparing with zzeitg's sun illuminated finches.
Are you doing the max to make sure you are isolating optical performance from other factors? I'm talking: big solid weighted tripod or, better, beanbag/sandbag on a solid surface like a wall; static subject; remote shutter release (the use of which is not emphasised as much as it should be IMO); good light (sun behind you) = 1/1000 min shutter. Then take a bunch of test pics at 5.6, f8, f11, and also see if there is visible distinction between AF and MF, the latter using magnified live view ideally with a loupe on the lcd (or at least shade the lcd). Pic 2 shows the test subject I put together (wishing I had a stuffed bird!) for my 400mm lens supertest (in progress), the flat banknote is to test resolution of fine detail and mitigate DoF issues - at eg 400mm and 10m distance the depth of the in focus region is only a few cm.
If there is a discrepancy between AF and MF then you will need to go through adjusting the AF.
Forum: Lens Clubs 03-10-2019, 07:00 AM  
The Mirror Lens Club!
Posted By marcusBMG
Replies: 992
Views: 372,534
You're welcome. I had a 55BB that showed clear signs of having had its front element removed. Its IQ was sub par. I think the tolerances on these are extremely tight. So I have avoided messing with the front element, IMO it's easier and less risky to separate the lens.
I don't bother with any of the generic mirrors. A sigma 600mm I sold earlier this year was comparable IQ to the tamrons. I'd like to check out a couple more of the soviet ones.
Forum: Lens Clubs 03-08-2019, 06:01 AM  
300mm plus Lens Club: discuss your long lenses
Posted By marcusBMG
Replies: 30,831
Views: 2,808,516
I merely wanted to clarify the distinction between posterisation and solarisation. The definitions I copied and pasted included the alt spellings.
Forum: Pentax SLR Lens Discussion 03-07-2019, 06:03 AM  
Need help urgently! Vivitar 24mm f2!
Posted By marcusBMG
Replies: 17
Views: 759
I can assure you all normal coatings are absolutely immune to acetone.
Forum: Lens Clubs 03-07-2019, 05:22 AM  
The Mirror Lens Club!
Posted By marcusBMG
Replies: 992
Views: 372,534
I have cleaned 55BB's by separating the lens at the helicoid (remove the distance scale - small screws). To avoid getting grease off the helicoid onto hands, wipes etc insert a piece of thin card into the lens front half.
IIRC you do need to mark the point of separation. Overall an easy lens to clean.
Forum: Pentax SLR Lens Discussion 03-07-2019, 04:54 AM  
Need help urgently! Vivitar 24mm f2!
Posted By marcusBMG
Replies: 17
Views: 759
Those marks look on the outside to me. try eg acetone.
Forum: Lens Clubs 03-07-2019, 04:33 AM  
300mm plus Lens Club: discuss your long lenses
Posted By marcusBMG
Replies: 30,831
Views: 2,808,516
Solarisation (often spelled Solarization) is the effect in photography in which the image recorded on a negative (or on a photographic print) is wholly or partially reversed in tone. Simply put dark areas appear light and light areas appear dark.

Posterization or posterisation of an image entails conversion of a continuous gradation of tone to several regions of fewer tones, with abrupt changes from one tone to another.


I would remark that the pics do appear to show signs of posterisation on my monitor. Most commonly caused I think by too much jpg compression.
Forum: Troubleshooting and Beginner Help 03-06-2019, 04:25 PM  
Any historic or known issues sigma DC lens (18-125mm) on a K10?
Posted By marcusBMG
Replies: 5
Views: 301
I should have been more specific this is the older version, screw drive.

Sigma 18-125mm F3.5-5.6 DC Lens Reviews - Sigma Lenses - Pentax Lens Review Database
Forum: Troubleshooting and Beginner Help 03-06-2019, 04:06 PM  
Any historic or known issues sigma DC lens (18-125mm) on a K10?
Posted By marcusBMG
Replies: 5
Views: 301
I have had a lens returned to me cos the buyer couldn't get it to work on his K10 - lens wasn't recognised, wouldn't autofocus. This is a sigma DC 18-125mm. There's no fault I can detect with the lens on my K3, fully functioning. Buyer said his sigma 28-80mm (KAF mount) works fine. Any insight anyone.. buyer isn't demanding a refund, I offered to send him my other one, but since there's no fault with the returned one, might simply run into the same issue...
Forum: Pentax SLR Lens Discussion 03-06-2019, 02:03 PM  
Safe to use soot on a lens?
Posted By marcusBMG
Replies: 19
Views: 790
negative. There is a small amount of activated charcoal on the tip - acts a bit like a dry detergent.
Normal optical wipes from your local supermarket are fine - check the packet and make sure they are solvent based, not water based.
See my lens pen review here

https://www.pentaxforums.com/accessoryreviews/sunpak-lenspen-lens-cleaner.html
Forum: Lens Clubs 03-03-2019, 05:55 AM  
Adaptall Mount Club (Tamron).
Posted By marcusBMG
Replies: 3,663
Views: 611,578
An anemone that blossomed during the mid-winter summer interlude just ended. K3-ii, F4. You can see the same pic + 1:1 pixel peep crop with a sigma superwide II 24mm for comparison here (nothing in it).
Forum: Lens Clubs 03-03-2019, 05:52 AM  
The Sigma Lens Club- All lenses
Posted By marcusBMG
Replies: 2,253
Views: 347,384
Sigma superwide II 24mm. An anemone that blossomed during the mid-winter summer interlude just ended. K3-ii, F4. You can see the same pic + 1:1 pixel peep crop with an adaptall 01B 24mm for comparison here (nothing in it in terms of resolution, rendering, bokeh with this is a bit smoother.).
If you have focus issues with this lens see my diy fix focus article here.
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 03-03-2019, 04:25 AM  
Mounting Takumar M42 lenses on a Sony A7r ii body...............
Posted By marcusBMG
Replies: 17
Views: 829
Link works fine on firefox on my PC (win 7, FF65). try eg chrome
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 03-02-2019, 06:14 AM  
Mounting Takumar M42 lenses on a Sony A7r ii body...............
Posted By marcusBMG
Replies: 17
Views: 829
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