|
Forum: Pentax K-3 & K-3 II
08-21-2018, 08:27 AM
|
| |
M33 at 1016mm focal length and M27 at 1300mm focal length. The K3 is a great astro camera.
|
|
Forum: Post Your Photos!
09-27-2017, 06:05 AM
|
| |
Sunrise at Quiraing on the Isle of Skye, last March during one of my Workshops on the Isle. Quiraing is a really enchanted place, where trees even grow horizontally out of hillsides :) Leica SL, Voigtlander 15mm and Formatt-Hitech Firecrest filters. Thanks for viewing, best regards
Vieri
|
|
Forum: Pentax K-3 & K-3 II
01-10-2018, 09:37 AM
|
| |
| |
|
Forum: Lens Clubs
11-23-2017, 02:47 PM
|
| |
Two quick tests I made of the Rokinon 135 F2 with the astrotracer. The first picture is M45, a single 50 s shot at F2.0. The second has the Flame, Horsehead and M42 and even M78 at the very left. 4 X 60 s iso 400 with K-50. In both images 3 darks and 3 flats were applied to the lights.
I'm really happy to see the 135 working so well with the astrotracer.
|
|
Forum: Pentax K-1 & K-1 II
05-06-2016, 12:48 PM
|
| |
some early morning shots (FA43)
 |
|
Forum: Pentax K-1 & K-1 II
05-06-2016, 10:43 PM
|
| |
I'll play your game, @edo ;)
|
|
Forum: Photographic Technique
10-21-2015, 08:55 AM
|
| |
My solution is to shoot all Auroras close to the car :lol:
[First image: Pentax K-3. DA* 16-50/2.8
Second image: Pentax LX. FA 31/1.8 Limited. Ektachrome 100VS at 200ISO]
 |
|
Forum: Photographic Technique
10-15-2015, 01:28 PM
|
| |
Excellent tips and very well written article.
Having lived in the arctics for 10 years, most things winter becomes second nature.
In terms of clothing, do what the inuits do in Northern Greenland.
Hunting trips on dogsleds for weeks in the deep of winter in temperatures below -40C and sleeping in tents is quite common.
I have travelled with them on several trips and it works, but you do look unusual :)
Personally i prefer the arctic expedition boots from sorell when you are out for multiple days in temperatures below -30C, but go far enough north and the locals swear by their lamb and mosk ox wool linned seal skin boots.
Ohh and this is what you look like in the morning, when you realise it is -32C just outside of your sleeping bag :)
 |
|
Forum: Pentax K-3 & K-3 II
04-01-2015, 03:23 AM
|
| |
| |
|
Forum: Pentax SLR Lens Discussion
01-23-2015, 02:07 PM
|
| |
Good news!
Today I received a notification from Sigma Germany that Sigma HQ acknowledged the problem and has already provided a fix:.
 Quote: 2015.01.23
Dear SIGMA 17-70mm F2.8-4 DC MACRO HSM | Contemporary PENTAX Users - Firmware Update of the Lens
Thank you for purchasing and using our products.
We have found that the SIGMA 17-70mm F2.8-4 DC MACRO HSM | Contemporary PENTAX does not function properly when the image stabilizing system on the camera body is used.
For those who own the lens, we are going to provide the firmware update free of charge.
Please note that all lenses shipped from our factory from now on will have the latest firmware.
We appreciate your continued support for our company and products.
[Product]
SIGMA 17-70mm F2.8-4 DC MACRO HSM | Contemporary PENTAX
[Phenomenon]
When the image stabilizing system on the camera body is used, the degree of image blur becomes bigger.
For further information, please contact your nearest authorized subsidiary / distributor of SIGMA.
For those who own the SIGMA USB DOCK, it is possible to update the firmware through SIGMA Optimization Pro 1.2. Source: https://www.sigma-photo.co.jp/english/new/new_topic.php?id=491
I must say I'm surprised how well Sigma has handled this issue - I didn't expect a solution so fast (and was worrying if it would be forthcoming at all...)! Many thanks to the diligent people at Sigma!:)
|
|
Forum: Pentax SLR Lens Discussion
01-07-2015, 03:14 AM
|
| |
I recently bought a Sigma 17-70 C and took lots of pictures with my K-5 II to decide whether I received a good copy that is worth keeping. The good news is that the lens delivered very nice image quality, AF was always spot on at all focal lenghts (I took my test shots at 17, 21, 31 and 70mm) and there was no sign of decentering or other optical or mechanical problems. However, I discovered a compatibility problem with Pentax’s Shake Reduction (SR) function that, much to my regret, left me no choice but to return this otherwise nice lens. Please read on...
The Problem:
It took me a while to figure this out - I first noticed that some shots at 17 and 21mm were not sharp. I first suspected optical problems, but further tests proved that the lens is generally very sharp there as well. If there, the unsharpness looked like it was caused by camera shake. What I failed to understand was how it was possible to have so much blurred pictures at 17 and 21mm while none taken at 31 and 70mm, even shot with the same shutter speed, showed any sign of it. Weird…
To provoke the issue I took a series of pictures at shutter speeds where SR really matters, e.g. 1/13 or 1/10 seconds at 17mm. Result: About 9 out of 10 images showed camera shake, some of them quite pronounced.
It looked like this (100% crop): http://i.imgur.com/m5CoJ03.jpg
Now it’s getting interesting! A cross-test with my DA 18-135 (@18) and DA 15 (also at 1/13 or 1/10 seconds) showed the opposite behaviour: 9 out of 10 images were pin-sharp, only 1 showed slight signs of camera shake. Back to the 17-70, this time with SR deactivated: Only about 5 out of 10 images were blurred, and to a lesser extent than with SR activated. This led me to the conclusion that somehow SR is actually making things worse at short focal lengths. But why is SR malfunctioning here? To find out, I took a closer look at the metadata of the images created by the lens.
To function correctly, Pentax’s SR needs to know the actual focal length of the lens. Reason: the longer the focal length, the bigger the countermovement of the sensor needs to be for a given amount of camera shake. Please note we’re dealing with two values here:
1. The “normal” focal length information that can be read with almost any image editor from the EXIF data.
2. The focal length used for the SR mechanism (this is found in the so-called “manufacturer notes” metadata).
Most of the time 1. and 2. will be identical, but a different value in 2. is needed e.g. for lenses with internal focusing whose actual focal length changes with focus distance. The SR mechanism always uses the 2. value.
Now the problem: The “normal” focal length information is transmitted by the 17-70 to the camera without issues, but the “SR focal length” is plain wrong at the short end. This can clearly be seen in the metadata, where “focal length” is always correct but “SR focal length” is wrong at shorter focal lengths (I tested 17 and 21mm; from 31mm upwards it seemed OK). See for yourself the metadata of three shots at 17 or 21 mm: http://imgur.com/a/EFjUt
While “normal” focal length is correctly reported as 17mm or 21mm for all, “SR focal length” can be any value from 31mm to 70mm(!). This obviously leads to a malfunctioning of the SR mechanism, which overcorrects the camera shake and thus blurs the image.
At longer focal lengths (31mm and above) both focal length values are identical in the metadata and SR seems to work correctly.
My guess is that Sigma forgot to ensure that this value is transmitted correctly. You have to remember that they do not officially licence the K-mount and rely on reverse-engeneering the communication protocols between lens and camera. It’s easy to forget a seemingly harmless value in the manufacturer notes. However, in this case it causes real damage and makes SR useless at shorter focal lengths. Even worse, it actually amplifies the camera shake (SA - Shake Amplification :eek:) and leaves the user no option but to disable SR at these focal lengths.
By the way, you can also see the weird SR behaviour in action during Live View: The image seems somewhat “jerky” and panning movements look really strange at the short end. If you zoom beyond 28mm or so the behaviour goes back to normal.
I strongly suspect this is a general issue with all copies of this lens and probably affects all Pentax camera bodies with SR. Unfortunately, all the images I found on the web from other Pentax users of this lens had most of their metadata stripped (Adobe products regularly do this) and no longer contained the manufacturer notes which show the “SR focal length” value. So to confirm the issue it would be great if owners of the lens could test their copy in the 17-21mm range to find out if this issue applies to all copies of the lens (and to all cameras). You can check the “SR focal length” value (both for JPG and Raw files) with programs like PhotoMe, or just upload them somewhere and I can check for you. Thanks!
Possible Solutions/Workarounds:
For now, the only option is to deactivate SR at shorter focal lengths because it does not reduce but actually amplifies camera shake. This won’t cause motion blur at shorter shutter speeds like 1/100 or above (where you wouldn’t need SR anyway :hmm:), but at speeds where SR matters it will actually work against you...
The Next Steps:
I guess the only party that can truly solve this problem is Sigma. Hopefully it is fixable with a firmware update of the lens. But I fear this will probably be regarded as a minor issue (I disagree!) that only applies to their least important supported camera mount.
As soon as others confirm the problem with their copies of the lens, I will notify my local Sigma representatives (Sigma Germany) of this issue and point them to this thread, and I encourage you to do the same in your part of the world. Maybe then we’ll have a chance that Sigma HQ takes notice of this problem and will try to fix it.
I will update this thread if I receive any news from Sigma regarding this problem.
Please note that I cannot do any further tests with this lens as I returned my copy to the seller. I will happily buy a copy again as soon as Sigma resolves this problem, because otherwise I really liked the lens.
-----------------
UPDATE:
Believe it or not, Sigma has already addressed this issue and published a firmware update that is supposed to fix the SR misbehavior. Kudos to Sigma for this quick reaction and for caring about their customers!
Further Information: https://www.pentaxforums.com/articles/pentax-related-news/sigma-addresses-17-...ion-issue.html
|
|
Forum: Troubleshooting and Beginner Help
04-13-2014, 10:31 AM
|
| |
yea, its a very close call. keep in mind both the corners and the center will not be sharper in the same shot due to the field curvature, which is extreme with this lens (meaning whatever the lens is projecting onto your sensor is not flat)
http://www.cheyennezjphotographer.com/wp-content/uploads/2013/07/Field-Curvature_LR.jpg
this means blue is your true infinity focus. the infinity mark should correspond to where the center achieves its optimal sharpness.
|
|
Forum: Pentax SLR Lens Discussion
12-09-2014, 03:17 PM
|
| |
Well. The Tamron 17-50 is a good option that does let you go to 2.8, and I find it extremely sharp at 2.8 and wide open. I'm not sure that is really wide enough for Northern Lights, but I never tried it myself.
When I was in Iceland shooting the Northern Lights, I used a Tamron 10-24, which is f/3.5 at the wide end (4.5 at the 24 end). The 10mm end was what I used the most, and I did find a big problem with the aperture ruining my ability to get the "curtain effect". I suppose I could have gotten a bit more detail if I used a shorter shutter speed, but I used ISO to get what I wanted out of my images.
The images below are a couple of examples from my trip. Not the best ones, but I wasn't concerned as much with the curtain effect, so I often went for longer shutter speeds to get the shot I wanted. Anyway, both of these images were shot with that Tamron 10-24, wide open at f/3.5, at ISO 3200 and 1600 with shutter speeds around 16 to 20 seconds. The camera was a K-5. I always used the 10mm end for my shots when I was out among the Northern Lights. I just felt I needed as much of the sky as possible. If I went back there, I'd probably try my 15 mm prime, but I'd be more concerned about it being wide enough rather than fast enough.
 |
|
Forum: Lens Clubs
09-22-2014, 09:56 AM
|
| |
| |
|
Forum: Lens Clubs
04-04-2014, 09:55 AM
|
| |
Enjoying my second copy of the Samyang 16mm f/2. First one got sent back for decentering issues. This one looks like a keeper.
Milky Way with the Pentax K-5 IIs and 16mm Samyang f/2 @ f/2.8 80 seconds exposure at ISO 1600.
 |
|
Forum: Lens Clubs
08-07-2013, 05:37 AM
|
| |
| |
|
Forum: Lens Clubs
05-27-2013, 09:31 AM
|
| |
Observed yesterday: a blue tit feeding its young in a tree hole, Lower Austria, DA* 300 and K-5 II, cropped.
Images 2, 3 and 4 are less than 0,2 seconds apart:
A closer look at the third image above:
BTW, this tiny bird must be travelling at an incredible speed. This next shot was taken at 1/2000 no more than 0,1 second before landing and there is still some morion blur left:
 |
|
Forum: Lens Clubs
05-19-2013, 11:45 PM
|
| |
Went a the local "Ecomuseum" (small zoo in Sainte-Anne-de-Bellevue, Qc http://www.ecomuseum.ca/en ), and had fun on this overcast day (best IMHO)... here's a couple of close shots of a Bald Eagle (almost no PP, just a bit cropped for position, and a bit sharpened)
Noble birds they are...
K20D + F* 300mm F/4.5
"+1 LIKE"
|
|
Forum: Lens Clubs
05-13-2013, 09:45 AM
|
| |
| |
