Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-28-2015, 01:10 PM   #31
Site Supporter
Stavri's Avatar

Join Date: Aug 2014
Location: at a Bean & Leaf
Photos: Albums
Posts: 1,662
QuoteOriginally posted by stevebrot Quote
The term is seldom used on this site, but "focus breathing" usually is described as a change in relative FOV as the lens focuses down from infinity. The term is a bit of a misnomer and is a property of many internal focus zoom lenses. For example, my Sigma 17-70 FOV at 70mm and 2 meters is about the same as a 50mm lens at the same distance.

Focus Breathing (Focal length variation with focus distance)- Bob Atkins Photography

What you are describing is called "focus shift". It is caused by residual spherical aberration and occurs when the lens stops down at exposure time. Usually, the shift is relatively small (a few millimeters +/- at plane of focus at common shooting distances) and is covered nicely by increased DOF. Where it becomes a problem is when doing macro work.


Steve
Focus shift is what I meant, thank you...

03-28-2015, 01:17 PM   #32
Forum Member




Join Date: Jan 2015
Posts: 77
Original Poster
BTW, maybe a bit off topic, but I got a $30 M 50mm f1.7 off eBay delivered today-oh my, this beast is stunning!! Just a quick sample pic (just autotone & resize only in PP) of my patio and I was just stunned! I'm so glad that I've switched to pentax system. Just need a little care for my K-3's autofocus, then there should be no complaint.
Attached Images
View Picture EXIF
PENTAX K-3  Photo 
03-28-2015, 03:52 PM   #33
Site Supporter
Stavri's Avatar

Join Date: Aug 2014
Location: at a Bean & Leaf
Photos: Albums
Posts: 1,662
QuoteOriginally posted by ychousa Quote
BTW, maybe a bit off topic, but I got a $30 M 50mm f1.7 off eBay delivered today-oh my, this beast is stunning!! Just a quick sample pic (just autotone & resize only in PP) of my patio and I was just stunned! I'm so glad that I've switched to pentax system. Just need a little care for my K-3's autofocus, then there should be no complaint.
The M 50/f1.7 and the super-tak 50/f1.4 are THE lenses that non-pentax users immediately think off when asked about pentax legacy glass. They have been adopted by Canonites and others because of the excellent performance/price. The M 50/1.7 is one of the best performing normal prime lenses across all brands.

I know these are in demand at the moment, buti think a super-takumar 50/f1.4 should be in every pentaxians cupboard, You haven't earned your moniker till you do.

Last edited by Stavri; 03-28-2015 at 03:59 PM.
03-28-2015, 05:53 PM   #34
Pentaxian




Join Date: Apr 2007
Location: Oklahoma USA
Posts: 1,503
QuoteQuote:
Does anyone have an experience like me? i'm kinda losing confidence in buying lenses.
Yes, and not just with Pentax lenses. I think there are several factors:

1. We have so many MP today that when you look at an image at 100%, you're demanding a lot more from the lenses than we did in the film era, or earlier digital eras. Since we can test much more thoroughly now than we could with film, at very low cost, we do;

2. With regard to 3rd parties, there's just less volume in Pentax (which is one reason so many third-party manufacturers have at least partly abandoned Pentax.) So some issues with AF and firmware etc. are just less likely to get worked out;

3. I'm guessing that Pentax (and maybe some other brands) manufacturing and QC haven't kept up with the increasingly complicated optical and mechanical complexity of newer lens designs.

Hopefully manufacturing quality and consistency will catch up with some of the engineering/design advances, and we'll have better quality, more consistent lenses soon.

03-28-2015, 06:07 PM   #35
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 25,864
QuoteOriginally posted by Eagle94VT Quote
I've never had a problem. 7 Pentax lenses. Had a sigma 70-300 once for a different mount - sucked so bad I didn't want it around to use even as a paper weight.
Sigma-70-300 Photos by Norm_Head | Photobucket









I guess everyone has their issues.
03-28-2015, 06:29 PM   #36
Site Supporter
Eagle94VT's Avatar

Join Date: Dec 2010
Photos: Albums
Posts: 199
I have a couple other Sigma's for my Canon. The 70-300 was the only lens I ever returned. The pictures looked like they came from my purple Holga. But I still take that purple Holga along with me on many outtings! A Hollywood edition I found for sale for $10.
One fruity day by eagle94vt

Last edited by Eagle94VT; 03-28-2015 at 07:28 PM.
03-28-2015, 08:13 PM   #37
Site Supporter
Stavri's Avatar

Join Date: Aug 2014
Location: at a Bean & Leaf
Photos: Albums
Posts: 1,662
The main reason why 3rd party manufacturers do just a terrible job making lenses in the K-mount, is that all the lenses get made during the weekend, (TRUE STORY) During the weekdays they built Canon and Nikon lenses, then on the weekend when they are all burnt up, they make the Pentax ones. They don't want to built lenses on the weekend, they wanna go home. But they Can't.....and it's sad

This is why the QC is so bad....(your heard it here fist)
03-29-2015, 05:57 AM   #38
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 25,864
QuoteOriginally posted by Stavri Quote
The main reason why 3rd party manufacturers do just a terrible job making lenses in the K-mount, is that all the lenses get made during the weekend, (TRUE STORY) During the weekdays they built Canon and Nikon lenses, then on the weekend when they are all burnt up, they make the Pentax ones. They don't want to built lenses on the weekend, they wanna go home. But they Can't.....and it's sad

This is why the QC is so bad....(your heard it here fist)
And here I though the Pentax lenses were all built Monday morning and Friday afternoon. The reality is so much worse than I thought. They are probably watching sports on their iPads while building the Pentax lenses. But,looking at the 10% return rate on the Tamron 70-200, there has to be a reason for that. Built on the weekends makes as much sense as anything.

03-29-2015, 11:18 PM   #39
Senior Member




Join Date: Feb 2014
Posts: 241
Just a thought but are you sure you not applying each adjustment to all lens. That would be easy to do. When making focus adjustment you have to specify it to only apply to that specific lens otherwise it will apply the adjustment to every lens. Something seems odd here. I've bought several new and used lens and have not yet found a need to adjust ant of them.
03-30-2015, 01:26 PM   #40
Site Supporter
Stavri's Avatar

Join Date: Aug 2014
Location: at a Bean & Leaf
Photos: Albums
Posts: 1,662
QuoteOriginally posted by TedW Quote
Just a thought but are you sure you not applying each adjustment to all lens. That would be easy to do. When making focus adjustment you have to specify it to only apply to that specific lens otherwise it will apply the adjustment to every lens. Something seems odd here. I've bought several new and used lens and have not yet found a need to adjust ant of them.
It could be that you're not looking hard enough or that you have indeed an excellent batch of lenses. Either way it's the personal satisfaction with your lenses performance that counts, not achieving the ultimate performance. Pixel peeping is no fun...
03-30-2015, 02:37 PM   #41
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 25,864
IN answer to your original question according to Lensrentals.com Pentax has the lowest frequency of repair rate in the industry.

That being said, I pick up my camera bag the other day, and my DA* 60-250 fell to the floor with a loud bump. It works fine but it had a slight bit of out of the ordinary resistance in one part of the zoom motion. Which has since disappeared. To use it now, you'd never know there was anything wrong with it. But it's a little bit noisier than tt was before. I could sell this to some unsuspecting soul and get a new one.... and it might be good for years to come, but, I plan to send it to have it checked out. It may be that right now my lens works fine, but because of a bit of barrels distortion, the WR seals aren't working. Any used piece of equipment you buy could have had a similar experience. It may even have been working when whoever sold it to you shipped it to you, and been damaged during shipping.

Personally, I simply don't buy used unless I get a fantastic price. It's simply not worth it.
03-30-2015, 03:46 PM   #42
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,844
Pentax usually rates quite highly for consumer satisfaction, including lenses:

Pentax DSLRs top global consumer satisfaction survey | Digital Camera World

Basing any findings on Pentax defect rates or AF largely on used lenses bought here or on eBay would be a mistake.

One also needs to be very rigorous in AF testing to get it right. What is your AF testing methodology? Poorly judged AF adjustments can make your AF worse.

Since the Canon T2i does not support AF micro-adjustment, maybe your good luck with lenses on Canon came from never being able to apply any micro-adjusts to them
03-30-2015, 04:59 PM   #43
Pentaxian
TaoMaas's Avatar

Join Date: May 2007
Location: Oklahoma City
Photos: Gallery | Albums
Posts: 3,197
QuoteOriginally posted by tibbitts Quote
We have so many MP today that when you look at an image at 100%, you're demanding a lot more from the lenses than we did in the film era, or earlier digital eras.
I think that's a big factor. The other thing that comes into play is focus. I could be wrong, but I don't lay all the blame at the feet of the lens. I think cameras could be having a hard time locking on or may be choosing the wrong area...plus I think there's a high degree of operator error. I'm not saying that this is the problem in this case...but I'm just sayin'.

Edited to add: I've never had a Pentax lens where I thought there was something wrong with it. In almost every case, the fault was mine. However, I will say that I don't really buy many brand new Pentax lenses. So maybe I've been lucky and have only bought used lenses where someone already had all the bugs sorted out. However, I've bought lenses in a WIDE variety of places...and my experience has always been the same.
03-31-2015, 05:34 AM   #44
Pentaxian




Join Date: Apr 2007
Location: Oklahoma USA
Posts: 1,503
QuoteOriginally posted by Stavri Quote
It could be that you're not looking hard enough or that you have indeed an excellent batch of lenses. Either way it's the personal satisfaction with your lenses performance that counts, not achieving the ultimate performance. Pixel peeping is no fun...
My guess is that a lot of users, even fairly serious enthusiasts, don't pixel peep in the extreme edges/corners, particularly with longer focal lengths, because they're more interested in subjects that are near the center. All of my lenses have had good center sharpness (obviously varying somewhat with the model of lens) given careful MF. Most have been ok about 2/3rd of the way to edge, but then mulitiple lenses have fallen down dramatically from there to one edge/corner or another. With zooms that often happens at only certain ranges of focal lengths or distances. So for someone who primarily makes certain types of portraits, animal photos, etc., what would be a huge problem to me might not be a problem at all to them. Similarly, PF from something like the Tamron 70-300 (which can be extreme under the right circumstances) that would be a huge problem for a bird enthusiast, tends to be less of a problem, at least percentage-wise, for me (although no PF at all would definitely be preferable.)
03-31-2015, 07:54 AM   #45
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,474
QuoteOriginally posted by Stavri Quote
It could be that you're not looking hard enough or that you have indeed an excellent batch of lenses.
...or both!

If a person looks hard enough and has the tools to do so, faults (or at least the perception of fault) will always be found. The OP posted an inquiry several weeks ago regarding some of the focus issues mentioned in this thread. After reviewing the example photos there, it is my conclusion that expectations may be a little skewed in regards to objects at distance and that the attempts at fine adjustment may be misdirected, improperly done, and the cause of the problems noted in this thread.

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/288693-m...-included.html


Steve

Last edited by stevebrot; 03-31-2015 at 08:05 AM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
35mm, 50mm, adjustment, af, camera, da, focus, front, lenses, lenses or 3rd, pentax, pentax help, photography, return, settings, steve, subject, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best Lenses your opinion wanted 3rd party lenses 'non pentax' Krusty Surfer Pentax SLR Lens Discussion 58 02-20-2015 05:25 PM
Why do 3rd party lenses vary so much in price between different mounts? Outis Pentax SLR Lens Discussion 8 12-01-2014 07:00 PM
If allowing 3rd party lenses in Pentax Lens Tournament ... starjedi Pentax SLR Lens Discussion 28 11-04-2014 06:22 AM
Have you compared the 80-320 to 3rd party lenses? scottax1 Pentax SLR Lens Discussion 10 10-24-2007 08:40 PM



All times are GMT -7. The time now is 01:36 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top