Forgot Password
Pentax Camera Forums Home
 

Showing results 1 to 25 of 300 Search:
Forum: Pentax SLR Lens Discussion 11-15-2019, 12:36 AM  
How is the sharpness of your K 500mm f4.5 on digital, if you have one?
Posted By glasbak
Replies: 29
Views: 1,411
Forum: Pentax SLR Lens Discussion 11-13-2019, 01:02 PM  
Spots in pictures from my SMC PENTAX DA 18-55 lens
Posted By glasbak
Replies: 19
Views: 746
Do the spots change when zooming to a different focal length ?
Forum: Pentax SLR Lens Discussion 11-02-2019, 03:53 AM  
What new lens would you purchase on release?
Posted By glasbak
Replies: 72
Views: 2,731
high end 50mm 1:2.8 macro with aperture ring (bellows usage) and proper mechanics to keep the optics aligned, so no crappy plastic as on the dfa50 macro..
Forum: Pentax SLR Lens Discussion 11-02-2019, 03:39 AM  
mm for shooting the moon
Posted By glasbak
Replies: 12
Views: 607
Rule of thumb : diameter of the full moon (or sun) on the sensor is 1% of the focal length.
Forum: Pentax SLR Lens Discussion 08-10-2019, 06:39 AM  
Which Pentax 100 macro?
Posted By glasbak
Replies: 31
Views: 1,541
And here they differ (look at the optical diagrams) : Pentax Short Telephoto Prime Lenses | The K-Mount Page
So, who to believe ?

And you are talking about the DFA100 WR, I have no experience with that lens, I did mention clearly the plastic aperture ring versions and never the WR version.

Some other hints for demanding macro photographers :
Avoid lenses with a plastic filter thread (easily damaged when attaching the lens in reverse, or attaching a ring flash)
Avoid lenses without aperture ring if you want to reverse a lens, or use it on bellows, controlling aperture becomes a nightmare.
Forum: Pentax SLR Lens Discussion 08-10-2019, 06:06 AM  
Which Pentax 100 macro?
Posted By glasbak
Replies: 31
Views: 1,541
The F and FA are quite metal, and of a very good build quality.
If I remember correctly, the FA 100 and DFA 100 have a different optical formula, the FA 50 and DFA 50 the same.
The DFA 50 and 100mm (the ones with aperture rings), are very plastic and built with double heliocoids, which keeeps the design compact, but as drawback an extra increase in play.

If you notice problems with these plastic lenses will depend on what you use them for.
If you shoot flowers and insects, or have an APSC sensor size, the drop in image quality goes probably unnoticed.
On my K1 and using it for reproduction, it is quite obvious, especially the portret mode shots show the most drop in resolution out of center.
Putting the camera on a reproduction stand, with the lens pointing down, so gravity does not pull the optics out of alignment give the best results.
The problem is not unique to the DFA 50 macro etc. Lots of optics with a lot of play in them suffer from the same problem (remember the DA 16-45 ? Pentax DA 16-45mm 1:4 ED/AL review: Digital Photography Review)
Forum: Pentax SLR Lens Discussion 08-10-2019, 02:39 AM  
Which Pentax 100 macro?
Posted By glasbak
Replies: 31
Views: 1,541
If you are serious about optical quality, avoid the plastic DFA 50 and DFA 100mm, the optics are OK, but the mechanics are not able to keep the optics proper aligned. If I can find a good FA50 macro, I will toss out the DFA50 macro.
Forum: Pentax SLR Lens Discussion 08-09-2019, 12:14 PM  
Pentax 50mm 1:1.4 m vs 50mm 1:1.4
Posted By glasbak
Replies: 19
Views: 1,165
The K version has the better mechanics(brass on aluminum in the focus heliocoid) and the radioactive yellowing/browning glass (hence the warmer cast),
Forum: Pentax SLR Lens Discussion 06-09-2019, 08:02 AM  
Which 135mm one to keep? smc pentax-m 3.5, Takumar (Boyonet) 2.5 or smc Takumar 3.5
Posted By glasbak
Replies: 18
Views: 1,443
The screw mount takumar is optical the best of the three on 'full frame', the lower edge performace of the M goes unnoticed on apc-c, build quality of the screw mount is the best, the bayonet takumar the worst (mine keeps getting grease on the aperture blades, even after several cleanings).
Forum: Pentax SLR Lens Discussion 05-26-2019, 10:52 PM  
Weird lens behaviour on Pentax K Mount (film SLR)
Posted By glasbak
Replies: 11
Views: 959
Could the error be lens speed related ?
Maybe something has come loose which prevents light of low speed lenses reach the light sensor in the chinon..
Forum: Pentax SLR Lens Discussion 05-08-2019, 11:39 AM  
SMC Pentax-m 35-70mm 2.8-3.5 Focus/ aperture mark not line up.
Posted By glasbak
Replies: 9
Views: 631
loosen the 3 screws in the knurled part, and then you can re position the barrel, or shift it up to see some internals.
Forum: Pentax SLR Lens Discussion 08-07-2018, 10:48 AM  
Faulty SMC Pentax AF Zoom 1:2.8 35~70mm
Posted By glasbak
Replies: 7
Views: 596
And this page may be of interrest too, clean the contacts ?
Forum: Pentax SLR Lens Discussion 01-14-2018, 02:19 AM  
Are K lenses better than their M and A counterparts?
Posted By glasbak
Replies: 23
Views: 2,079
So, you found my very first webpage, with the pictures I made 20 years ago !

About mechanical finish, there is a degradation in finish of the M lenses over the various production batches (cost cutting), the very first generation of the M 1:1.7 50mm has the best finish.
Forum: Pentax SLR Lens Discussion 01-13-2018, 06:24 AM  
Are K lenses better than their M and A counterparts?
Posted By glasbak
Replies: 23
Views: 2,079
Already in the film days (20 years ago?) I had the next statement :

No M lens which replaced a similar K lens, optically outperforms that K lens, they are usually worse.

Why ?
The M generation had as major selling point compactness, and that had its optical consequences for the edges of the image field.
Central performance of a M lens is generally good, that is why the APS-C users don't notice this difference, on 24x36 thats different.
Lots of A lenses are repackaged M lenses.

Mechanically the K lenses which had their roots in takumars have brass in their focus heliocoid, the M generation has aluminum only. Aluminum on aluminum goes very bad without grease.
Forum: Pentax SLR Lens Discussion 10-12-2017, 10:12 AM  
throium glass lenses
Posted By glasbak
Replies: 60
Views: 4,552
I think it is just the takumar optics with bayonet, and not a repair job, because one of these lenses is more that 30 years in my possession, so probably less that 10 years old when I bought it, deteriorating cement takes usually more time,
Forum: Pentax SLR Lens Discussion 10-12-2017, 07:09 AM  
throium glass lenses
Posted By glasbak
Replies: 60
Views: 4,552
I have two PENTAx-K 1:1.4/50 lenses, both suffer from browning and are radioactive (verified with a radiation meter), just as their smc takumar predecessors.
So it is not strange they perform similar.
Forum: Pentax SLR Lens Discussion 04-04-2017, 09:58 AM  
Leaflet:Pentax Lenses and Accessories
Posted By glasbak
Replies: 11
Views: 1,019
I also have scanned a few, and put them on the web, 15 years ago already
LBA addicts, I am not resposible for what happens if you click !
Forum: Pentax SLR Lens Discussion 10-30-2016, 04:06 AM  
K-series vs M-series image quality-wise?
Posted By glasbak
Replies: 20
Views: 2,022
My statement is that there are very few M lenses superior to the K lens they replaced, although the center performance is generally good, the more compact optical constructions probably did have a negative effect on the edge and corner performance (which you won't notice much on APS-C).
Forum: Pentax SLR Lens Discussion 08-22-2016, 12:24 PM  
Samyang/Rokinon 24mm tilt-shift samples, anyone?
Posted By glasbak
Replies: 11
Views: 1,092
Yes, the raw, but why do you ask, what do you expect from it.
Forum: Pentax SLR Lens Discussion 08-20-2016, 07:07 AM  
Samyang/Rokinon 24mm tilt-shift samples, anyone?
Posted By glasbak
Replies: 11
Views: 1,092
It is not easy to get the result you want with this lens, just an experimental shot
Forum: Pentax SLR Lens Discussion 07-22-2016, 11:53 AM  
Lens CA and filter?
Posted By glasbak
Replies: 17
Views: 1,216
I did some tests and experiments in the past here, here and here

Filters can help a bit, but there is not a simple cure which will help all combinations of lens/camera/sensor and light situation.
Forum: Pentax K-1 06-05-2016, 12:28 AM  
Request/query for Takumar-enthusiast K-1 users.
Posted By glasbak
Replies: 34
Views: 3,340
My 50/1.4 takumars are more yellowed in the center than the edges, the positive lenses have the most glass there.

And about the emission, I assume most alpha radiation stays trapped in the glass, only the particles emitted at the glass/air surface will make a change to come out, gamma rays you get from the complete volume of the glass.
Forum: Pentax SLR Lens Discussion 06-04-2016, 08:50 AM  
NEWSFLASH! Pentax Doesn't Make Lenses O.O
Posted By glasbak
Replies: 75
Views: 6,235
I don't care, and happily use my voigtlander lens on my K-1.

But if the pentax brand name survives, it will probably go the voigtlander way, which was in a similar situation half a century ago.
And I do not think that anything sold under the voigtlander name has anything to do with the original company or products.
Forum: Pentax SLR Lens Discussion 06-03-2016, 05:58 AM  
NEWSFLASH! Pentax Doesn't Make Lenses O.O
Posted By glasbak
Replies: 75
Views: 6,235
Pentax does not make glass.
Pentax does not make lenses.
Pentax does not make camera's.
Nowadays, Pentax is just a label used by Ricoh for camera and lenses related stuff.
Before Ricoh, it was Hoya who sold camera's using the pentax label.
Before Hoya acquired Pentax, Pentax did make lenses and camera's.
Forum: Pentax SLR Lens Discussion 05-27-2016, 10:37 PM  
Radioactive Lens Measurements
Posted By glasbak
Replies: 17
Views: 7,646
I did my own tests some time ago, and be prepared, if you test a lens which appears radioactive, but populair believe is that it is not radioactive, they won't believe you.
Rumours on the internet are more trustworthy than actual measurements.
Search took 0.02 seconds | Showing results 1 to 25 of 300

 
Forum Jump


All times are GMT -7. The time now is 02:39 PM. | 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