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Forum: Pentax SLR Lens Discussion 04-04-2017, 07:21 AM  
Corner Sharpness: Tamron 17-50 @17mm
Posted By Dan
Replies: 6
Views: 520
I wrote my response before you posted your update saying that the problem was with the lower left corner. I edited my response accordingly. This does seem to be a de-centering problem with your copy, but I doubt that Tamron will fix it. Of course it doesn't hurt to try, since it is still under warranty.

It's always a good idea to test lenses for decentering when you first get them so that they can be returned as defective during the return period. It is very rare for a manufacturer to fix a decentering problem under warranty. This is a very common flaw. I've had to return about half of the lenses I've purchased due to severe decentering. The problem seems worse among zooms. I've had the best luck with the Pentax limiteds.

Dan
Forum: Pentax SLR Lens Discussion 04-04-2017, 07:09 AM  
Corner Sharpness: Tamron 17-50 @17mm
Posted By Dan
Replies: 6
Views: 520
The Tamron 17-50 suffers from extreme field curvature at 17mm. Here is a summary of the problem from the Photozone review:

"Unfortunately the lens has a less than desirable characteristic - at 17mm it suffers from very strong field curvature which can render the outer corners out-of-focus." source: Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Nikon) - Review / Test Report - Analysis

I believe that this is what you are experiencing. When the center is sharp the corners are out of focus. In short, it is a design flaw, not a problem with your specific copy of the lens. There's nothing they can do to fix it, other than redesigning the lens.

Dan

Edit: Since you now say that the problem is worse in the lower left corner, the problem is probably exacerbated by de-centering. The decentering is, of course, a problem with your copy, but it's very likely that Tamron will claim that it is "within specs".
Forum: Pentax Price Watch 11-25-2016, 08:37 AM  
Black Friday SD Card Deals!
Posted By Dan
Replies: 5
Views: 1,040
It is the "Video Class" of the card. It signifies that the card can record at a minimum of 30 MB/s, which is adequate for 4K video.

I hope this helps,

Dan
Forum: Pentax DSLR Discussion 11-16-2016, 11:17 AM  
The Great JPEG Shootout! (Canon, Nikon, Sony, Fuji, iPhone, Pentax, Olympus, Panasoni
Posted By Dan
Replies: 90
Views: 6,356
In my experience, Pentax JPEGs are really quite bad. In the test they used the K-70. While I haven't tried that camera, I do have its predecessor, the K-S2. The K-S2 JPEGs are so bad that I quit shooting RAW+JPEG. I found that I could never use the JPEGs, and so they were just a waste of card space. Maybe I would have been happier with the quality if I just shot JPEG and wasn't able to compare them to the results I was getting from the RAW files.
Forum: Pentax K-1 11-03-2016, 10:50 AM  
So I broke down...
Posted By Dan
Replies: 15
Views: 1,463
Where did you get that price on the K-1? Those look like B&H product codes, but I'm seeing $1,946.95 everywhere I look, including B&H.
Forum: General Photography 10-07-2016, 02:14 PM  
Check your hue ability - TEST
Posted By Dan
Replies: 53
Views: 2,509
I scored a zero, but I cheated. I have a good monitor. :)
Forum: Pentax K-70 08-30-2016, 07:04 AM  
Red CA, a problem?
Posted By Dan
Replies: 9
Views: 725
I agree that it's very obvious. But it only affects the brushes in the upper left corner of the image. If you examine the same style brushes in the lower right part of the image the nasty fringing is gone, even though the lighting and reflections are very similar. This suggests that it is not a sensor problem, but rather a problem with lens. The lens elements are not perfectly centered. This can affect not just sharpness, but fringing as well.

Why does this not show up with the K3-II? Two possibilities come to mind. First, as others have mentioned, it could be that they used different copies of the lens. Another possibility is that the same lens was focused slightly differently in the two tests. Even very small differences in focusing can affect fringing.

As someone who has done a lot of my own lens testing, I can tell you that it is an extremely difficult thing to do. Small changes in the setup can have noticeable effects on the results. Moreover, modern sensors have such high resolution that they can reveal small flaws in lens assembly and small differences in focus.

Dan
Forum: Pentax K-1 02-19-2016, 07:15 PM  
Pentax K-1 "Thank you" Thread
Posted By Dan
Replies: 104
Views: 7,764
I will thank the design team (and the executives who priced it) in the one way that is most meaningful: I WILL BUY IT!!

Dan
Forum: Lens Clubs 02-19-2016, 01:16 PM  
The 15mm Limited controls my mind - club
Posted By Dan
Replies: 10,681
Views: 1,649,849
I have the Pentax M 20mm f/4, which is nice little lens. Given how old the design is I would not have expected it to be sharp on FF, but examples I have seen from the lens mounted on a Sony a7 suggest otherwise. When stopped down it is surprisingly good! At f/8 it seems adequately sharp and it renders images nicely. It is also reasonably resistant to flare. Since I almost always shoot wide angle lenses at f/8 (or there abouts) I think that I will be able to use it successfully on the K-1. And did I mention that it is a tiny lens? :)

Dan
Forum: Pentax K-1 02-17-2016, 09:48 PM  
K-1: On-demand body lighting helps you see what you're doing
Posted By Dan
Replies: 26
Views: 2,007
This is a very useful feature. What a nice touch!
Forum: Pentax News and Rumors 02-17-2016, 09:13 PM  
Pentax K-1 Officially Announced
Posted By Dan
Replies: 1,591
Views: 172,591
It looks like they nailed it. A great camera at a phenomenal price. At that price I suspect that they will get a lot of early adopters. :)

Thanks Ricoh!
Forum: Lens Clubs 02-17-2016, 06:52 AM  
The 15mm Limited controls my mind - club
Posted By Dan
Replies: 10,681
Views: 1,649,849
I find that I can get the sides and corners to be sharp at f/8 by focusing behind the central focus point. In most cases this requires focusing past infinity, which is possible with my copy (and I believe most copies) of the DA15. The center may end up just slightly less sharp, but not enough to matter. I set the aperture to f/8 and crank the focus ring all the way to the hard stop. This results in an image that is sharp across the frame.

Dan
Forum: Lens Clubs 02-15-2016, 06:29 PM  
The 15mm Limited controls my mind - club
Posted By Dan
Replies: 10,681
Views: 1,649,849
Outstanding photos; particularly the first one. These are great examples of why so many of us love the DA15. They also bring me back to the time I lived in Oslo. Takk for det!

Dan

---------- Post added 02-15-16 at 05:31 PM ----------



Great shots with a great lens. Very interesting perspective! Thanks for posting these photos.

Dan

---------- Post added 02-15-16 at 05:33 PM ----------



Outstanding photo! Great composition. You really nailed this shot.

Dan
Forum: Pentax K-S1 & K-S2 01-04-2016, 09:36 AM  
K-S2 Firmware Updates?
Posted By Dan
Replies: 4
Views: 740
Forum: Post Your Photos! 12-21-2015, 04:47 PM  
Misc Christmas Greetings from Norway
Posted By Dan
Replies: 10
Views: 455
God jul og godt nyttår!
Forum: Pentax Price Watch 11-27-2015, 06:18 PM  
Pentax K-3 II Black Friday @ B&H
Posted By Dan
Replies: 51
Views: 5,016
I would rather pay an extra 50 bucks and not have to deal with a rebate. I also know from past experience that I can return an item to B&H without any hassle if the need arises. Peace of mind has a dollar value, which in my case exceeds 50 bucks. :)

I prefer the B&H deal.

Dan
Forum: Photographic Industry and Professionals 02-14-2015, 11:56 AM  
How many deferred purchases because of FF announcement?
Posted By Dan
Replies: 28
Views: 2,137
I was about to buy the Sony Alpha a7II but decided to wait for CP+ to see if Pentax had something to announce. I'm glad I waited! :lol: I can wait a bit longer for the camera to be released. In the meantime I may pick up one of the new lenses, after I see some reviews.

I think that Ricoh made the right call in announcing the camera. Too many folks were switching systems. This will help stop the bleeding.

Dan
Forum: Pentax News and Rumors 02-12-2015, 08:45 AM  
Unveiling of the Full Frame Prototype
Posted By Dan
Replies: 912
Views: 120,082
It means that the SR mechanism will be used to increase the effective megapixels, resulting in a 1.5-2x increase in image resolution. The files will be up to 4x larger. It can only be used when the camera and subject are not moving.
Forum: Photographic Technique 02-11-2015, 03:47 PM  
Wow factor, are some of these overdone?
Posted By Dan
Replies: 70
Views: 4,322
The first one is overdone; the rest of them are FANTASTIC. Bravo!

"Too much is never enough."

Dan
Forum: Pentax Full Frame 02-05-2015, 09:32 AM  
“I will not buy the FF, if _____"
Posted By Dan
Replies: 181
Views: 12,382
I will not buy the FF if it has a light leak and/or sprays oil on the sensor. Sorry Nikon. :p

I fully intend to buy the FF Pentax. I am waiting patiently for it to hit the market. As a Pentax user, I've become well practiced at waiting patiently. :)

Dan
Forum: Pentax SLR Lens Discussion 01-03-2015, 10:25 AM  
What lens is on your camera right now?
Posted By Dan
Replies: 287
Views: 16,322
I had to check. The SMC DA 40mm Limited is on my camera right now. Usually it would be the 21mm Limited, which is my "normal" lens. When I shot film the 30mm K was my normal lens. :)

Dan
Forum: Pentax K-S1 & K-S2 11-06-2014, 09:52 PM  
Can the K-S1 do landscapes?
Posted By Dan
Replies: 34
Views: 3,364
That's a stunning photograph. But there's no way it was taken with the lowly K-S1. Must have been full frame, or at the very least a K-3. :-)
Forum: Pentax News and Rumors 08-14-2014, 05:52 AM  
Photokina!
Posted By Dan
Replies: 877
Views: 84,834
He downsampled the K-3 output to 16mp and he used a mediocre lens. I think his results show that if you intend to use mediocre (or crappy) lenses and downsample your output then there is no benefit to a 24 megapixel sensor over a sensor with a somewhat lower pixel density.

While it may seem that I am being critical of his test, I actually think that it is relevant for a lot of DSLR users. Lots of folks use lenses that are mediocre (at best), and many folks shrink down their images for web display, or to display the full image on their computer screens. Only a relatively small percentage of users make large prints. Moreover, even with large prints it can be difficult to discern differences in pixel density. Given this, pixel density is not a reason for most users to choose a K-3 over a K-5IIs. Of course the K-3 has other advantages, and the higher resolution of the sensor is of use to those who have invested in first-rate glass and like to pixel peep.

Dan
Forum: Troubleshooting and Beginner Help 05-07-2014, 06:57 AM  
K3 and photoshop cs2
Posted By Dan
Replies: 10
Views: 972
I'm not sure why you are having problems with 8.3, but if you can open the dng files in Lightroom I would use that. You should be able to save the files as jpegs or tifs. I would save as a tif, and then edit the tif in Photoshop.

Dan
Forum: Troubleshooting and Beginner Help 05-06-2014, 09:32 AM  
K3 and photoshop cs2
Posted By Dan
Replies: 10
Views: 972
Adobe DNG converter 8.4 is not compatible with Vista. (See the "System Requirements.) You need to download Adobe DNG converter 8.3, which is the only version that is compatible with both the Pentax K-3 and Windows Vista. Here is the download page:

Adobe - Adobe Camera Raw and DNG Converter : For Windows : Adobe DNG Converter 8.3

Dan
(a Linux user :D)
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