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Canon Full-Frame Users are Butchering Pentax MF Lenses!
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PostPosted: Tue Jan 17, 2012 11:33 am    Post subject: Re: Mirrorless sensor size headed the wrong direction Reply with quote
ZoneV wrote:
I am very happy with 14/2.8, 17/3.5, 18/4, 24/1.4, 25/2.8 mm lenses on the sensor format they are designed for - and not only a smaller part of that.

A full frame camera with short register could be interessting, but I am not sure wheter I would like the electronic viewfinder. Furthermore I probably would not like the cost of this camera, or other things about it.


As much as I want a full frame mirrorless, I know it will show serious problems with many (but not most) old lenses.

A retrofocal wide-angle lens (i.e., wide for an SLR) is essentially a wide with an inverted telephoto to reproject the image -- this means more elements and distortions are harder to manage. Pre-digital short rangefinder lenses that take advantage of the short flange distance to not be retrofocal typically have projection angle issues that cause problems with the microlens arrays in digital cameras. The result is that modern wides generally are optically much better, especially at the edges. Better coatings, aspherics, and better computer design can really help wides. Of 100+ old lenses, I have nothing under 24mm that has IQ competitive with the Sony NEX kit zoom on APS-C... and on full frame, old wide lenses will generally be worse. Zooms have similar issues.

In summary, size isn't all that matters in lens design -- film and sensors have very different properties to optimize for and some things do get better in newer lenses.


PostPosted: Tue Jan 17, 2012 12:10 pm    Post subject: Reply with quote
nixland wrote:

So Jeff, could you give me some advice how to use & modify Pentax-A 50/1.2 on Canon 5D without cutting the aperture lever.
I want to preserve the mount especially the lever....


good on you Smile


I hope this helps: https://plus.google.com/photos/115725524945054615587/albums/5200318360689315345?banner=pwa
a photo from there, it doesn't look difficult:


arrived there through these links which don't seem to directly link any more: http://www.fredmiranda.com/forum/topic/667236/0#5974824 but one will find inspiration and encouragement, thank you Steven Lins.

a few more links given which may be worth checking out: http://photo.net/canon-eos-digital-camera-forum/00O7Id

be so kind Wink


PostPosted: Tue Jan 17, 2012 1:39 pm    Post subject: Re: Mirrorless sensor size headed the wrong direction Reply with quote
ProfHankD wrote:
...Pre-digital short rangefinder lenses that take advantage of the short flange distance to not be retrofocal typically have projection angle issues that cause problems with the microlens arrays in digital cameras. The result is that modern wides generally are optically much better, especially at the edges.....


Oh yes, the microlenses. I am happy, my EOS 5D classic seems to have very simple - or bad microlenses in terms of optimization.
But I am thinking about sensors without microlenses. Should be better for small DOF too Smile
This is one reason why I think about using film.


PostPosted: Wed Jan 18, 2012 9:39 am    Post subject: Reply with quote
kuuan wrote:
nixland wrote:

So Jeff, could you give me some advice how to use & modify Pentax-A 50/1.2 on Canon 5D without cutting the aperture lever.
I want to preserve the mount especially the lever....


good on you Smile


I hope this helps: https://plus.google.com/photos/115725524945054615587/albums/5200318360689315345?banner=pwa
a photo from there, it doesn't look difficult:


arrived there through these links which don't seem to directly link any more: http://www.fredmiranda.com/forum/topic/667236/0#5974824 but one will find inspiration and encouragement, thank you Steven Lins.

a few more links given which may be worth checking out: http://photo.net/canon-eos-digital-camera-forum/00O7Id

be so kind Wink


Thanks for the info.

By the way I wonder if the FA lens construction is the same with the Pentax-A? especially the aperture & it's lever.


PostPosted: Wed Jan 18, 2012 6:58 pm    Post subject: Re: Mirrorless sensor size headed the wrong direction Reply with quote
ProfHankD wrote:
I'm pretty sure many old lenses will look a lot worse in the corners of full frame sensors, so the benefit over APS-C might not be as big as hoped given the resolution we're now used to on APS-C... but I'd still like a full frame sensor too.

Not really. Sharpness is weaker in the corners, usually, but for many types of images it's not that important. Having the full field of view of the lens, including the vignetting, curvature of field and such can give a very different, more interesting look compared to the results from a crop camera, where everything but the center is left out. Full frame lenses often lose a lot of their 'character' on crop cameras.


PostPosted: Wed Jan 18, 2012 9:59 pm    Post subject: Reply with quote
nixland wrote:

Thanks for the info.

By the way I wonder if the FA lens construction is the same with the Pentax-A? especially the aperture & it's lever.


see this Pentax A f1.7/50 lens, looks quite straight forward: http://homepage.mac.com/jpelling/50mm/1.7fix.html


PostPosted: Thu Jan 19, 2012 9:49 am    Post subject: Reply with quote
kuuan wrote:
nixland wrote:

Thanks for the info.

By the way I wonder if the FA lens construction is the same with the Pentax-A? especially the aperture & it's lever.


see this Pentax A f1.7/50 lens, looks quite straight forward: http://homepage.mac.com/jpelling/50mm/1.7fix.html


Thanks for the link. The aperture lever looks as one part with the aperture (?) ... kind of bad news.


PostPosted: Thu Jan 19, 2012 9:58 am    Post subject: Reply with quote
You could try to contact Eric Hendrikson for info about the A50/1.2.
He is the first I contact regarding Pentax lenses.

http://pentaxs.com/


PostPosted: Thu Jan 19, 2012 11:34 pm    Post subject: Re: Canon Full-Frame Users are Butchering Pentax MF Lenses! Reply with quote
Jeff Zen wrote:
Yes, Canon full-frame users are butchering many, many vintage Pentax MF lenses mostly for video uses.
They are cutting off the tabs on the rear of lenses so that they clear the mirror. Many of these wounded lenses are reappearing on the market.

Some buyers have reportedly purchased lenses where the tabs have been cleverly glued back on, only to have them break off inside their cameras.

This is not only dishonest but can ruin your camera. Please beware!


Sigma DSLR users also remove the "tabs", after which they fit straight onto the SA mount. The "tabs" of course being the metal AA lever and its plastic or Aluminium protector outcrop. I've only done it to a couple of PK mount lenses and only one of them was an actual Pentax lens...The SMC-M 50mm f1.7...A lens with such poor build quality it literally fell apart in my hands!...Have'nt touched a Pentax lens since!!
I use my MTO 1000A 1100mm f10.5 on the SA mount via a T2-PK adapter, but T2 adapters dont have any "tabs" to remove so it probably does'nt count. I also converted my Carl Zeiss 50mm f1.7 Planar T* to PK mount.


PostPosted: Fri Jan 20, 2012 9:34 am    Post subject: Reply with quote
hoanpham wrote:
You could try to contact Eric Hendrikson for info about the A50/1.2.
He is the first I contact regarding Pentax lenses.

http://pentaxs.com/


Thanks for the info. I have contacted him, explaining the problem.

I've just read his reply and unfortunately he only said "The lever can be removed" with no further explanation or information.

Based on his short reply I think he himself doesn't care about cutting the lever Smile


PostPosted: Fri Jan 20, 2012 9:42 am    Post subject: Reply with quote
He is retired pentax repair in us. Super busy with all old lenses from pentax forums member.
Why dont you contact Charles, repair man of Attila?


PostPosted: Fri Jan 20, 2012 7:02 pm    Post subject: Reply with quote
Pentax MF Lens Users are Butchering Full-Frame Canons!
http://www.pentaxforums.com/forums/pentax-dslr-discussion/130552-pentax-full-frame-digital-slr-camera-well-sort.html



nixland wrote:

Thanks for the link. The aperture lever looks as one part with the aperture (?) ... kind of bad news.


I have not yet disassembled many Pentax lenses (simply because it was not necessary) but afaik the lever construction as seen on the FA limiteds is limited to those.

My advice:
- Butcher your camera, see link above.
- Exchange the A50/1.2 for a cheaper K50/1.2 if you have to butcher the lens. Same optics and is better built. Leave the A lenses to Pentax users who can make use of the A-feature.
- Bend the aperture lever. Maybe you will also have to remove the plastic shield, I think that depends on the adapter you are using.
I never tried that, but I can imagine that whether that works or not does also depend on the adapter you are using.


PostPosted: Fri Jan 20, 2012 8:04 pm    Post subject: Reply with quote
Crying or Very sad
The problem is that he has already the K50/1.2!


PostPosted: Fri Feb 03, 2012 10:13 am    Post subject: Reply with quote
Yeahh! Finally I got my A 50/1.2! Smile

I've asked the local lens repairman week ago and it's a good news that he said the lever could be removed and no need to cut it. So it's a reversible modification.
Tomorrow I'll bring the lens to him.
Meanwhile I'll use it on my Canon 60D (below). Sorry for bad lighting and white balance Smile



PostPosted: Fri Feb 03, 2012 10:18 am    Post subject: Reply with quote
could you ask him how easy the pin can be removed?

if pentax is waiting too long for a FF, i might get a cheap 5d.

seems like you mis focus a bit in the photo.
dof is razor thin at f1.2


PostPosted: Fri Feb 03, 2012 10:34 am    Post subject: Reply with quote
hoanpham wrote:
could you ask him how easy the pin can be removed?

if pentax is waiting too long for a FF, i might get a cheap 5d.

seems like you mis focus a bit in the photo.
dof is razor thin at f1.2


I think it's a bit more complex but let's wait till tomorrow.
The important thing is that the repairman said the lever removal without cutting is "no problem" with full confidence Smile


PostPosted: Sat Feb 04, 2012 11:37 am    Post subject: Reply with quote
Not a good news Sad
The repairman gave up. He tought it would be easy like other lens but after he opened the aperture guide fin ring he had no idea how to open it further. He never open a pentax-A lens before.

I will bring my beat up A 50/1.4 (super cheap, cheaper than takumar 50, has separation marks) to the repairman to study the pentax-A lens structure first Smile

Meanwhile I will do lens test between the A 50/1.2 versus my other 50-55/1.2 lens using Canon 60D (no problem with lever).


PostPosted: Sun Feb 05, 2012 8:48 am    Post subject: Reply with quote
As already mentioned in this thread, why not BEND the aperture lever?

Did this to a smc-a 50/1.7; Removed the tab and simply bent over the aperture lever to 180°.
I later wanted to sell the lens, so I bent the lever back and tested it. It doesn't look perfect, but works 100%. The buyer was very happy with the lens.


PostPosted: Sun Feb 05, 2012 9:50 am    Post subject: Reply with quote
pst wrote:
As already mentioned in this thread, why not BEND the aperture lever?

Did this to a smc-a 50/1.7; Removed the tab and simply bent over the aperture lever to 180°.
I later wanted to sell the lens, so I bent the lever back and tested it. It doesn't look perfect, but works 100%. The buyer was very happy with the lens.


Sorry I forgot to mention before. The repairman has tried to bend the lever too (only 45 degree) but it still interfere with the mirror.

Ok then, I'll try to bend 180 degree. Or it came up in my mind to bend it twice (forming L shape). Wish me luck Smile


PostPosted: Sun Feb 05, 2012 9:53 am    Post subject: Reply with quote
By the way I am about to battle the A vs the K using 60D. If the A is not significantly better than K then I am thinking to sell the A.


PostPosted: Sun Feb 05, 2012 10:50 am    Post subject: Reply with quote
casualcollector wrote:
And just about all kinds of DSLR users are grinding, hacking, whacking and destroying Canon FL/FD manual focus lenses to achieve infinity focus. Far worse than what's being done to PK lenses.

Before you grind, change your mind. Send your FL/FD mount (and other) lenses to The Casual Collector's Home for Aging Optics. Here, your experienced lenses will lead an active retirement, creating colorful images in the Florida sunshine. They will be cared for and excercised and there will be no fear of dismemberment, disembowlment or organ harvesting.

PM for shipping details.


Bahaha, gold! Very Happy


PostPosted: Sun Feb 05, 2012 2:09 pm    Post subject: Reply with quote
Theoretically, the A has slightly better coating. Be careful when you straight the pin back. The position of the pin is direct couple of the aperture. I have one lens that had been bend and had to open up to fix it. Both versions is so little different that you have to look hard to find. My A50/1.2 might be a bit more contrast than K50/1.2, but also depends on light condition...


PostPosted: Sun Feb 05, 2012 3:30 pm    Post subject: Reply with quote
hoanpham wrote:
Be careful when you straight the pin back. The position of the pin is direct couple of the aperture. I have one lens that had been bend and had to open up to fix it.


Uh oh ... I hope the repairman didn't straighten up wrongly yesterday.

hoanpham wrote:
Theoretically, the A has slightly better coating. Both versions is so little different that you have to look hard to find. My A50/1.2 might be a bit more contrast than K50/1.2, but also depends on light condition...


Just did a quick test. Just 3 shots, outdoor. The A is significantly sharper or more contrasty, but the bokeh looks harsher than the K. I think it's the consequence of the lens over correction (?) ... the sharper the lens the harsher the bokeh (has pronounced ring).
It's dilemmatic Smile I'll do more tests Smile

Thanks a lot for the helpful tips hoanpham.


PostPosted: Sun Feb 05, 2012 3:37 pm    Post subject: Reply with quote
nixland wrote:
Not a good news Sad
The repairman gave up. He tought it would be easy like other lens but after he opened the aperture guide fin ring he had no idea how to open it further. He never open a pentax-A lens before.

I will bring my beat up A 50/1.4 (super cheap, cheaper than takumar 50, has separation marks) to the repairman to study the pentax-A lens structure first Smile

Meanwhile I will do lens test between the A 50/1.2 versus my other 50-55/1.2 lens using Canon 60D (no problem with lever).

It's not hard to open Pentax M or A lens. The problem is, that aperture leveler is part of aperture control ring or is riveted to it. Only Pentax lenses, where the leveler is non destructively removable are F/FA/DA lenses, where the leveler is fixed with two screws.
My opinion is, that it's not worth to butcher Pentax K mount lenses. You can always sell it and get comparable or better lens at same price from different manufacturer.


PostPosted: Sun Feb 05, 2012 3:56 pm    Post subject: Reply with quote
BRunner wrote:
nixland wrote:
Not a good news Sad
The repairman gave up. He tought it would be easy like other lens but after he opened the aperture guide fin ring he had no idea how to open it further. He never open a pentax-A lens before.

I will bring my beat up A 50/1.4 (super cheap, cheaper than takumar 50, has separation marks) to the repairman to study the pentax-A lens structure first Smile

Meanwhile I will do lens test between the A 50/1.2 versus my other 50-55/1.2 lens using Canon 60D (no problem with lever).

It's not hard to open Pentax M or A lens. The problem is, that aperture leveler is part of aperture control ring or is riveted to it. Only Pentax lenses, where the leveler is non destructively removable are F/FA/DA lenses, where the leveler is fixed with two screws.
My opinion is, that it's not worth to butcher Pentax K mount lenses. You can always sell it and get comparable or better lens at same price from different manufacturer.


@BRunner: Thanks for the info about the lever is part of aperture control. So, it's not removable then. Bending is the only option.

And I'll think about your opinion too.

So, my case is closed Smile
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