Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-23-2018, 03:44 AM   #301
Pentaxian
gazonk's Avatar

Join Date: Feb 2009
Location: Oslo area, Norway
Photos: Gallery | Albums
Posts: 3,746
QuoteOriginally posted by D1N0 Quote
Nope, and if I was it wouldn't show CA. It's not like you add CA in post.
Aperture’s CA correction certainly can add enormous amounts of CA if I accidentally use it wrong (but that would be lateral CA then).

05-23-2018, 04:25 AM   #302
Pentaxian
D1N0's Avatar

Join Date: May 2012
Location: ---
Photos: Gallery
Posts: 6,802
Then maybe aperture autocorrects CA, lightroom can't add more CA than there is on import with no lens profile applied.
05-23-2018, 06:25 AM   #303
Veteran Member




Join Date: May 2016
Photos: Gallery | Albums
Posts: 2,722
QuoteOriginally posted by BigMackCam Quote
Really? Interesting... I actually haven't had a single unreliable (both generally, and specifically relating to AF accuracy) screw-drive lens for my Pentax gear, and I have "a few" of them

I do own an old consumer-grade, screw-drive Minolta AF lens for my Sony A-mount gear that has some play in the mechanism, and that occasionally leads to some inaccuracy through physical movement after AF has locked...

In any case, the new D-FA50/1.4 isn't screw-drive, is it? Or am I missing the point of your post?
Your gear must be working better than mine then, cause my da 50 and Tamron 70-200 definitely are not consistent. And dfa 15-30 in anything but bright daylight either, and it's a modern lens.

Hopefully 50 1.4 will be better in this regard being the * modern prime

---------- Post added 05-23-18 at 06:29 AM ----------

QuoteOriginally posted by jatrax Quote
In what way? As far as trouble free operation I do not think you can begin to compare them to in lens motors. Lenses with motors have a failure rate, no matter what brand. Screwdrive? I think I can remember a single complaint on this forum of a screw drive failure and that might have been impact damage. That is about as reliable as anything I can think of.


As far as accurate focus? I guess we could debate that. I find the newer lenses with motors to 'seem' to be a little more precise compared to older screwdrive. But I'm not sure that is really true or just my impression. I suspect the stepping is finer on modern lenses versus the older screwdrive. But that also was if I remember improved somewhere around the K-3 with a faster screwdrive motor.
All I know is my own experience with my gear, and I'm sharing it. If people are not having those issues with their gear, then I must be in "luck" once again with my gear being faulty (I've had terrible experience with 15-30 that's thoroughly documented in other threads).

---------- Post added 05-23-18 at 06:31 AM ----------

QuoteOriginally posted by reh321 Quote
Don't all the new lenses contain in-lens motor, so we can finally put screw drive behind us?
28-105 and 15-30 aren't perfect either. Maybe I'm expecting too much, but in my opinion an expensive combo such as K-1 and 15-30 shouldn't miss focus in bright day light at all, even it doesn't happen 100% of the time
05-23-2018, 07:14 AM   #304
Digitiser of Film
Loyal Site Supporter
BigMackCam's Avatar

Join Date: Mar 2010
Location: North East of England
Posts: 20,576
QuoteOriginally posted by awscreo Quote
Your gear must be working better than mine then, cause my da 50 and Tamron 70-200 definitely are not consistent.
My own DA50 can also be a little inconsistent at times, i.e. occasionally missing focus. It's nothing to do with reliability of screw drive, though... there's something about the AF algorithm and that particular lens.

As for the Tamron 70-200, they are infamous for copy-to-copy variation, especially so far as front and back-focusing at different focal lengths is concerned. If you're lucky enough to get one that requires minimal or no adjustment at both ends, it's a great lens... but I returned two copies for this very reason and ended up paying the extra to buy a DA*60-250. Again, that front and back focusing issue is nothing to do with screw drive reliability - it's alignment and manufacturing tolerances with the lens...


Last edited by BigMackCam; 05-23-2018 at 11:41 AM.
05-23-2018, 07:17 AM - 2 Likes   #305
JPT
Pentaxian




Join Date: Jan 2012
Location: Tokyo
Photos: Gallery
Posts: 2,817
QuoteOriginally posted by Kunzite Quote
Thanks for your impressions; reasonable as always.
Was it faster than the usual Pentax lens? From Pentaxforums' Youtube video, I believe it should be... not to PLM level though.
Well, I only had limited time to use the DFA 50, and I was more focused on trying out the Dynamic Pixel Shift of the K-1 mark 2 at the time. My impression was that it was faster than most Pentax lenses, especially DA* series SDM. The fastest focusing lens I have is the DA 18-135 and the new lens is certainly faster than that. The 55-300 PLM, which I don't own but have tried, is significantly faster still. I did not attempt to test how the DFA 50 does AFC. I don't think it will come as a disappointment.

Ricoh keeps mentioning that the new lenses are built to be ready for future generations of cameras. My speculation is that part of the reason these lenses are so late to arrive is that they are being optimized on prototypes of cameras with a new AF system. That's when we'll see what they are really capable of.
05-23-2018, 07:29 AM - 1 Like   #306
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 40,442
QuoteOriginally posted by JPT Quote
Well, I only had limited time to use the DFA 50, and I was more focused on trying out the Dynamic Pixel Shift of the K-1 mark 2 at the time. My impression was that it was faster than most Pentax lenses, especially DA* series SDM. The fastest focusing lens I have is the DA 18-135 and the new lens is certainly faster than that. The 55-300 PLM, which I don't own but have tried, is significantly faster still. I did not attempt to test how the DFA 50 does AFC. I don't think it will come as a disappointment.

Ricoh keeps mentioning that the new lenses are built to be ready for future generations of cameras. My speculation is that part of the reason these lenses are so late to arrive is that they are being optimized on prototypes of cameras with a new AF system. That's when we'll see what they are really capable of.
Which would also explain why the K-3 upgrade is taking so long. I suspect the APS-c flagship will be the first recipient of the new, faster AF system, and perfecting it is part of what is taking so long.
05-23-2018, 07:59 AM   #307
Pentaxian




Join Date: Oct 2010
Photos: Gallery | Albums
Posts: 6,241
I thoughtthat for K-1 m2 they made some fundamental changes to algorythm for Safox. This tendency to focus to background or AF C focusing and so on. They did kind a admit also that it has been quite faulty. Great thing is that tey really are working on it. Not just adding new things and not repairing foundations. Every pentaxian is avare of lackings of Pentax cameras and how to work around them. Also how to make sure that focus is correct. Some do bracketing, I’d suggest also focus bracketing, one more just in case, eh.

New AF will be needed with new premium lenses and system for Pentax. Also for this lens. And should I say especially for this.

05-23-2018, 09:09 AM   #308
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Washington Cascades
Photos: Gallery | Albums
Posts: 12,991
QuoteOriginally posted by awscreo Quote
All I know is my own experience with my gear, and I'm sharing it. If people are not having those issues with their gear, then I must be in "luck" once again with my gear being faulty (I've had terrible experience with 15-30 that's thoroughly documented in other threads).
You did not answer my question. Are you having issues with screwdrive lenses not working or not focusing accurately? Two completely different things IMHO.


And throwing the 15-30 into this is very confusing as it is not a screwdrive lens. I'm not trying to argue with you just understand what it is you are trying to say.


Sorry you don't like the 15-30, my experience with that lens, so far, has been very different. It's currently my favorite.
05-23-2018, 09:49 AM   #309
Veteran Member




Join Date: May 2016
Photos: Gallery | Albums
Posts: 2,722
QuoteOriginally posted by jatrax Quote
You did not answer my question. Are you having issues with screwdrive lenses not working or not focusing accurately? Two completely different things IMHO.


And throwing the 15-30 into this is very confusing as it is not a screwdrive lens. I'm not trying to argue with you just understand what it is you are trying to say.


Sorry you don't like the 15-30, my experience with that lens, so far, has been very different. It's currently my favorite.
Screw drive lenses do no focus accurately, not all the time, but enough to be noticeable.

I like the lens, but I had bad luck with de centered copies, I'm on my third one and it's in repairs with precision camera right now.
05-23-2018, 10:06 AM   #310
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Washington Cascades
Photos: Gallery | Albums
Posts: 12,991
QuoteOriginally posted by awscreo Quote
Screw drive lenses do no focus accurately, not all the time, but enough to be noticeable.
I'm sure lots of people would disagree with that statement. But if they do not work for you at least we now have lenses with motors.


And sorry about your 15-30. I hesitated a long time before buying it, mostly because of the weight. But after two trips with it I am absolutely delighted. Sharp, fast and accurate. But it sure is heavy................
05-23-2018, 02:37 PM   #311
Veteran Member
MJKoski's Avatar

Join Date: Aug 2016
Posts: 1,784
Screw drive belongs to screw driver, not hires digital camera. It simply does not have enough accuracy for critical sharpness should some semi-intelligent logic some day provide useful AF. Why? The gears are sloppy as hell and have bad tolerances. For example 100mm WR macro does not hit exact same spot twice. Not even in LV.

Nikon pro-series (D3 etc.) have so much torque that front element can fall off from 85/1.8 AF-D lens. That is brutal screw driving.
05-23-2018, 03:51 PM   #312
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Washington Cascades
Photos: Gallery | Albums
Posts: 12,991
QuoteOriginally posted by MJKoski Quote
Screw drive belongs to screw driver, not hires digital camera. It simply does not have enough accuracy for critical sharpness should some semi-intelligent logic some day provide useful AF. Why? The gears are sloppy as hell and have bad tolerances. For example 100mm WR macro does not hit exact same spot twice. Not even in LV.
Appreciate your opinion.
05-23-2018, 04:27 PM - 5 Likes   #313
Digitiser of Film
Loyal Site Supporter
BigMackCam's Avatar

Join Date: Mar 2010
Location: North East of England
Posts: 20,576
QuoteOriginally posted by MJKoski Quote
Screw drive belongs to screw driver, not hires digital camera.
Of course, you're entitled to your opinion (though I dread to learn what you think of manual focus lenses, given that).

I can't deny, I prefer more modern drive methods too, but screw drive works absolutely fine for me. Like I said, you have your opinion, and that you're entitled to.

QuoteOriginally posted by MJKoski Quote
It simply does not have enough accuracy for critical sharpness should some semi-intelligent logic some day provide useful AF. Why? The gears are sloppy as hell and have bad tolerances. For example 100mm WR macro does not hit exact same spot twice. Not even in LV.
Here, however, you are - with respect - plain wrong.

Every single one of my modern screw drive lenses - both for K-mount and Sony A-mount - has been calibrated for AF fine adjustment on multiple bodies using a SpyderLENSCAL. And every one of them - the DFA100/2.8 included - reliably achieves accurate focus at their fastest aperture settings, from starting positions at both minimum focus distance and infinity, using either PDAF or LV CDAF. If there's any focus inaccuracy, it ain't from the lenses. And with a dedicated focus test chart, the camera AF algorithms (which are already pretty intelligent) have no problem either... so I can only imagine you're basing your claims on less controlled testing.

Actually, most of my older screw drive lenses - like my copy of the FA50/1.4 and Minolta AF 50/1.4 - are just as reliable and accurate as the newer ones. I do have an old Pentax F28-80 with vicious torque, and that occasionally overshoots very slightly - but not very often. It's an exception compared to the rest of my fairly extensive lens collection.

If your lenses are "sloppy as hell and have bad tolerances", maybe they need servicing. Or maybe there's a specific or specialist photographic activity you haven't mentioned, where you might have the ghost of a point re screw drive accuracy. If so, it certainly doesn't affect general day-to-day photography, based on my own experience.

I'd respectfully suggest you don't make blanket statements and draw hasty conclusions based purely on your own lens copies and photographic activities (as with the Irix lens we previously discussed). Whilst your intentions may be noble enough, it risks spreading inaccurate information to the wider audience.

Last edited by BigMackCam; 05-23-2018 at 04:56 PM.
05-23-2018, 06:54 PM   #314
Veteran Member




Join Date: Dec 2016
Posts: 602
I wonder I know they said summer release but exactly when anyone know? Also did the delay of the 50 push back the 11-18 * too?

Regarding screw drive is a tad louder but is reliable... Can’t fault it. However the DC is nice and quick/quiet.
05-23-2018, 06:58 PM - 5 Likes   #315
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 19,325
QuoteOriginally posted by MJKoski Quote
Screw drive belongs to screw driver, not hires digital camera. It simply does not have enough accuracy for critical sharpness should some semi-intelligent logic some day provide useful AF. Why? The gears are sloppy as hell and have bad tolerances. For example 100mm WR macro does not hit exact same spot twice. Not even in LV.

Nikon pro-series (D3 etc.) have so much torque that front element can fall off from 85/1.8 AF-D lens. That is brutal screw driving.
I've yet to find a lens that has zero depth of field, even wide open, so the fact that screw drive focus doesn't hit the the exact spot twice is a big ho-hum and goes into the "so what?" file.

If you are having problems achieving focus with screw drive lenses there could be explanations other than the technology. Perhaps your individual equipment is faulty, or you need to reevaluate your technique?
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!
art, breath, control, degree, delay, development, fa, fa*, hd, hd pentax-d, lens, lenses, nikon, pentax, pentax news, pentax rumors, pentax-d, people, photography, production, quality, ricoh, sdm, sigma, systems, time, users, wait
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
HD Pentax-D FA★ 25mm f/1.4 - 50mm f/1.4 - 85mm f/1.4 DC AW Mistral75 Pentax SLR Lens Discussion 43 07-26-2022 05:52 AM
Update on the optical scheme of the new HD PENTAX-D FA 50mm f/1.4 SDM AW maw Pentax News and Rumors 43 04-27-2018 12:56 PM
pentaxrumors.com reports new HD PENTAX-D FA ★ 50mm F1.4 likely to be released soon Madaboutpix Pentax Full Frame 17 01-24-2018 12:10 PM
Official image sample from the HD Pentax-DFA★ 50mm F1.4 SDM AW uploaded Madaboutpix Pentax SLR Lens Discussion 2 12-05-2017 05:36 PM
★★NOW IN STOCK★★Pentax K-5 Limited Edition★★ Chuck-B&H Ask B&H Photo! 11 03-31-2011 05:29 AM



All times are GMT -7. The time now is 08:51 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