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Pentax 50mm f1.2 K aberration monster or normal behaviour?
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PostPosted: Fri Dec 02, 2022 6:54 pm    Post subject: Pentax 50mm f1.2 K aberration monster or normal behaviour? Reply with quote
Hi all!

I am new to this forum, at least with posting, I have been reading it a lot for the last two years since I got hooked up to MF lenses...

I would appreciate a lot any help, advice or input from older and wiser members with experience with these types of lenses.

SO, I have recently acquired Pentax 50mm f1.2 lens in K mount, pre-M version. I have read a lot about the lens before I got it. Lens is in full working order. No fungus, scratches, balsam separation or haze. When looking through the lens in direct light glass elements are crystal clean.

I am aware of all kinds of aberrations and softness and stuff ("character") while taking pictures with lens wide open at f1.2, and I was OK with that. However, the amount of chromatic aberrations I am getting from this lens is just so overwhelming, that I am suspecting I have a lemon.

I am having trouble uploading images to this post, so I have put them in an album on flickr: https://www.flickr.com/photos/194575947@N08/albums/72177720304157409

I am getting a lot of chromatic aberrations in wide apertures (pictures #1 & #3), and not so wide apertures like f4-ish (picture #4). Especially in tree branches against white sky. And a lot of purple fringing in top corners at apertures where I did not expect any aberrations, like in f8 (picture #2).

I have also made a closer inspection of the glass elements today, and when light is not coming directly through the lens, there seems to be a lot of tiny, very tiny bubbles in the glass element that is located just beneath the front element. I always thought these bubbles cannot affect the IQ. However, on the last picture you can see that these artefacts in the glass in that particular lighting condition look like a lot of tiny black dots. I repeat, these dots are completely invisible when looking directly through the lens in daylight.

Please, if you have experience with this lens, can you please tell me if this is normal behaviour for the 1.2 lens, or there might be something strange going on?

I greatly appreciate any response to this post!

Thank you very much in advance!

I am having trouble uploading pictures to this post! can someone help out?

#1


#2


#3
[img][/img][/b]


PostPosted: Fri Dec 02, 2022 7:47 pm    Post subject: Re: Pentax 50mm f1.2 K aberration monster or normal behaviou Reply with quote
sdek1 wrote:
Hi all!

I am new to this forum, at least with posting, I have been reading it a lot for the last two years since I got hooked up to MF lenses...

I would appreciate a lot any help, advice or input from older and wiser members with experience with these types of lenses.

SO, I have recently acquired Pentax 50mm f1.2 lens in K mount, pre-M version. I have read a lot about the lens before I got it. Lens is in full working order. No fungus, scratches, balsam separation or haze. When looking through the lens in direct light glass elements are crystal clean.

I am aware of all kinds of aberrations and softness and stuff ("character") while taking pictures with lens wide open at f1.2, and I was OK with that. However, the amount of chromatic aberrations I am getting from this lens is just so overwhelming, that I am suspecting I have a lemon.

I am having trouble uploading images to this post, so I have put them in an album on flickr: https://www.flickr.com/photos/194575947@N08/albums/72177720304157409

I am getting a lot of chromatic aberrations in wide apertures (pictures #1 & #3), and not so wide apertures like f4-ish (picture #4). Especially in tree branches against white sky. And a lot of purple fringing in top corners at apertures where I did not expect any aberrations, like in f8 (picture #2).

I have also made a closer inspection of the glass elements today, and when light is not coming directly through the lens, there seems to be a lot of tiny, very tiny bubbles in the glass element that is located just beneath the front element. I always thought these bubbles cannot affect the IQ. However, on the last picture you can see that these artefacts in the glass in that particular lighting condition look like a lot of tiny black dots. I repeat, these dots are completely invisible when looking directly through the lens in daylight.

Please, if you have experience with this lens, can you please tell me if this is normal behaviour for the 1.2 lens, or there might be something strange going on?

I greatly appreciate any response to this post!

Thank you very much in advance!

I am having trouble uploading pictures to this post! can someone help out?

#1


#2


#3
[img][/img][/b]


Now should be visible.
Welcome aboard!!


PostPosted: Fri Dec 02, 2022 7:52 pm    Post subject: Reply with quote
ok. thank you very much!
I have two more pictures to upload.
can I edit the original post, or should I upload them here:


#1


#2


PostPosted: Fri Dec 02, 2022 9:12 pm    Post subject: Reply with quote
The aberrations on the picture of the keybord are longitudinal chromatic aberrations ( LoCA or bokeh fringing) .
They are not surprising on such a fast lens. It should be better when you stop down f 2 or f2.8 or…shoot black and white.


PostPosted: Fri Dec 02, 2022 11:47 pm    Post subject: Reply with quote
dealt with:


You can expect this kind of behavior from vintage bright lenses. No ED or Aspherical glass elements yet.


PostPosted: Sat Dec 03, 2022 12:09 pm    Post subject: Reply with quote
D1N0 wrote:
dealt with:


You can expect this kind of behavior from vintage bright lenses. No ED or Aspherical glass elements yet.


This is indeed longitudinal chromatic aberration, fairly normal for a fast lens of that vintage, and part of the character you can either learn to embrace, or spend ages trying to correct for (difficulty depending on the particular image.)

Correcting for LoCA is very difficult if nigh-impossible. As D1N0 demonstrated it can been dealt with in the in-focus area of the keys reasonably successfully, but is still very evident in the out-of-focus contrast areas of the keys (i.e. the purple-shift on the out-of-focus keys nearer the lens vs the green-shift on the out-of-focus keys furthest away from the lens. Also still visible in other areas like the green-shift on the contrast areas/edges of the white (cushion/pillow?) in the background.

The other kind of chromatic aberration, lateral chromatic aberration (LaCA, also often referred to as purple-green fringing), is largely determined by the image distance away from the paraxial area of the frame hence more obvious in the corners of the frame, and correction can therefore be (often, not always) successfully achieved based on lateral distance of an image point away from the centre of the frame. Most PP software therefore allows for fairly simple controls to try and correct for LaCA easily/automatically.

The longitudinal chromatic aberration you see here (LoCA, also referred to as bokeh-fringing) is largely governed by the longitudinal distance of every subject from the (field) plane of focus. Nigh impossible to easily/automatically correct for afterwards unless original subject distance information is also available for every image point in the frame.

Of course the most "annoying" area(s) can be dealt with one-by-one, like in the example provided by D1N0.


PostPosted: Sat Dec 03, 2022 1:06 pm    Post subject: Reply with quote
To me it doesn’t look all too bad, except the image of the keyboard which is easily corrected in post. If you want close to optical perfection you may take a look at modern lenses.


PostPosted: Sat Dec 03, 2022 3:00 pm    Post subject: Reply with quote
caspert79 wrote:
To me it doesn’t look all too bad, except the image of the keyboard which is easily corrected in post. If you want close to optical perfection you may take a look at modern lenses.


Well , even with modern fast lenses , there will be LoCA . The real apochromatic fast lenses are very rare.
There is, for example, the Voigtländer Apo Lanthar 50mm f2 but it is a f2 not a f1.2.

@DN10 good job in removing them but it can very difficult if not impossible as mentionned above.

Lateral AC are much easier to remove .


PostPosted: Sat Dec 03, 2022 8:11 pm    Post subject: Reply with quote
I know it's obvious, and I know it's not a solution, but this is one reason why black and white and vintage glass is a great combination.

Signed,
Black and White Lover

Smile


PostPosted: Sat Dec 03, 2022 9:11 pm    Post subject: Reply with quote
Thank you all for your insights! Much appreciated!
I also posted the same question to dpreview site.
Got almost identical answers.

In the last two years I shoot only old glass, never actually used good modern lenses. This was my most expensive buy so far, and I perhaps expected too much. Obviously, my expectations were formed this way due to my limited experience. What I learned so far is that these 1.2 lenses are quite specific. So, no other way for me but to get to speaking terms with this lens by shooting much more pictures and in different situations. Knowing that these aberrations are normal to this lens makes me at peace and alert me to think about lens and its limitations while taking pictures. I consider it as a challenge rather than limitation.

This morning I took it for a walk and already have some pictures that I am quite OK with. So, I'll share it below. Pictures are just converted in Adobe bridge to jpg, no post processing.

Thank you once again for your time and help!


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PostPosted: Sat Dec 03, 2022 10:27 pm    Post subject: Reply with quote
Like 1 Like 1 Beautiful countryside! I like #5 -- looks like you had to squat to see that -- and #6


PostPosted: Sat Dec 03, 2022 10:34 pm    Post subject: Reply with quote
I shoot this lens on Pentax K-1. Well, this lens is special because it is very fast. You need practice with it and the results will come. This is bokeh monster lens, great for portraits. It can be great at f1.2. Also, it can give some very nice close up photos with close up filter. Being f1.2 lens it is lens which gives you some special powers or I'd say some special bragging rights. Owning a f1.2 lens provides a great feeling and you did a good job acquiring it. It will make you inspired to go out and shoot more. Some of my samples with this special lens are below. Don't give up on this lens because for every lens you can easily show it's weaknesses and then become disappointed but with some careful use the strengths will shine. Good luck.

























PostPosted: Sat Dec 03, 2022 10:53 pm    Post subject: Reply with quote
Indigo82 wrote:
I shoot this lens on Pentax K-1. Well, this lens is special because it is very fast. You need practice with it and the results will come. This is bokeh monster lens, great for portraits. It can be great at f1.2. Also, it can give some very nice close up photos with close up filter. Being f1.2 lens it is lens which gives you some special powers or I'd say some special bragging rights. Owning a f1.2 lens provides a great feeling and you did a good job acquiring it. It will make you inspired to go out and shoot more. Some of my samples with this special lens are below. Don't give up on this lens because for every lens you can easily show it's weaknesses and then become disappointed but with some careful use the strengths will shine. Good luck.


Thanks for sharing, these are really great!
I am inspired, and I already started to practice.

But, what do you mean by close up filter?
I did not hear about that.
Do you have any to recommend specifically for this lens?

Thanks again for your insight and help!


PostPosted: Sat Dec 03, 2022 11:20 pm    Post subject: Reply with quote
Thank you Smile

I used generic 52mm filter thread close up + 4 filter which is basically an additional concave lens which is screwed at the front of the main lens.



Even those cheap ones found on AliExpress will do the work. I found this more convenient for my use in the field than macro extension tubes.


PostPosted: Sun Dec 04, 2022 10:40 am    Post subject: Reply with quote
Indigo82 wrote:
Thank you Smile

I used generic 52mm filter thread close up + 4 filter which is basically an additional concave lens which is screwed at the front of the main lens.



Even those cheap ones found on AliExpress will do the work. I found this more convenient for my use in the field than macro extension tubes.


Close-up lenses are often under-appreciated/underrated, compared to extension tubes & bellows. Each has its own advantages & drawbacks, but certainly the better-quality achromat doublet close-up lenses of the main brands can give very good results, and are a lot less bulk and weight to carry around compared to extension tubes or bellow.

But even the cheaper non-branded ones like Indigo82 already mentioned above can be of good use, as long as the inferior coatings don't give ghosting/flare problems. Bear in mind that for most in-the-field close-up images the subject will be central in the frame, such as insects, flowers, etc. A slight loss of sharpness in the corners or some extra field curvature rarely is a problem in those circumstances.


PostPosted: Sun Dec 04, 2022 10:57 pm    Post subject: Reply with quote
Indigo82 wrote:
Thank you Smile

I used generic 52mm filter thread close up + 4 filter which is basically an additional concave lens which is screwed at the front of the main lens.

Even those cheap ones found on AliExpress will do the work. I found this more convenient for my use in the field than macro extension tubes.


Great!
Thanks. I will try it.

Can I ask you one more question?
I was wondering about that picture of swan you posted above. By the shape of bokeh balls I would say picture was taken with wide open lens. I took some swan pictures with this lens; it was broad daylight and I got very strong chromatic aberrations along the edges of white swan feathers. In your picture there are none of the aberrations whatsoever. Did you remove it in post processing?


PostPosted: Sun Dec 04, 2022 11:04 pm    Post subject: Reply with quote
RokkorDoctor wrote:

Close-up lenses are often under-appreciated/underrated, compared to extension tubes & bellows. Each has its own advantages & drawbacks, but certainly the better-quality achromat doublet close-up lenses of the main brands can give very good results, and are a lot less bulk and weight to carry around compared to extension tubes or bellow.

But even the cheaper non-branded ones like Indigo82 already mentioned above can be of good use, as long as the inferior coatings don't give ghosting/flare problems. Bear in mind that for most in-the-field close-up images the subject will be central in the frame, such as insects, flowers, etc. A slight loss of sharpness in the corners or some extra field curvature rarely is a problem in those circumstances.


Thank you for your insight!
Highly appreciated!


PostPosted: Mon Dec 05, 2022 12:01 am    Post subject: Reply with quote
sdek1 wrote:
Indigo82 wrote:
Thank you Smile

I used generic 52mm filter thread close up + 4 filter which is basically an additional concave lens which is screwed at the front of the main lens.

Even those cheap ones found on AliExpress will do the work. I found this more convenient for my use in the field than macro extension tubes.


Great!
Thanks. I will try it.

Can I ask you one more question?
I was wondering about that picture of swan you posted above. By the shape of bokeh balls I would say picture was taken with wide open lens. I took some swan pictures with this lens; it was broad daylight and I got very strong chromatic aberrations along the edges of white swan feathers. In your picture there are none of the aberrations whatsoever. Did you remove it in post processing?


You already said it. It was broad daylight. You will get strong contrasts and aberrations along them. The picture of the swan seems to be have been taken at dusk. Much more sedate lighting a softer contrasts so less aberrations.


PostPosted: Mon Dec 05, 2022 8:52 am    Post subject: Reply with quote
sdek1 wrote:
Indigo82 wrote:
Thank you Smile

I used generic 52mm filter thread close up + 4 filter which is basically an additional concave lens which is screwed at the front of the main lens.

Even those cheap ones found on AliExpress will do the work. I found this more convenient for my use in the field than macro extension tubes.


Great!
Thanks. I will try it.

Can I ask you one more question?
I was wondering about that picture of swan you posted above. By the shape of bokeh balls I would say picture was taken with wide open lens. I took some swan pictures with this lens; it was broad daylight and I got very strong chromatic aberrations along the edges of white swan feathers. In your picture there are none of the aberrations whatsoever. Did you remove it in post processing?


On this picture the swan is in the shade and receive no backlights. So no reason for lareral CA.


PostPosted: Mon Dec 05, 2022 9:29 pm    Post subject: Re: Pentax 50mm f1.2 K aberration monster or normal behaviou Reply with quote
sdek1 wrote:
Hi all!

I am new to this forum, at least with posting, I have been reading it a lot for the last two years since I got hooked up to MF lenses...

I would appreciate a lot any help, advice or input from older and wiser members with experience with these types of lenses.
]


Picture #3 looks terrific if it's at f1.2 and I dare to say this is as good as it gets for early 1980s non-aspheric technology.

As for the chromatic aberrations, they look more as interacton with a weak (or even non-present) anti-aliasing filter on the digital camera. Which camera are you using?

I would bet that film wouldn't show such problems.


PostPosted: Tue Dec 06, 2022 12:16 pm    Post subject: Re: Pentax 50mm f1.2 K aberration monster or normal behaviou Reply with quote
flavio81 wrote:


Picture #3 looks terrific if it's at f1.2 and I dare to say this is as good as it gets for early 1980s non-aspheric technology.

As for the chromatic aberrations, they look more as interacton with a weak (or even non-present) anti-aliasing filter on the digital camera. Which camera are you using?

I would bet that film wouldn't show such problems.


Thanks for info.

If you refer to picture #3 from my later post (the one with grass), yes, I think that was at 1.2 or maybe just one click closed. I can't remember.

I use Sony a7 ii. Do you think crhomatic aberrations could be caused in part by this camera?


PostPosted: Tue Dec 06, 2022 12:49 pm    Post subject: Reply with quote
All photos except close up macro shots are made at f1.2. It was Pentax K-1 full frame camera as mentioned in my first post.

Some more photos all at f1.2 except close up macro that is at f5.6.

It's not quite easy to photograph a moving swan at f1.2 by focusing manually.

Anyhow, I just wanted to say in this post that every lens has it's strengths and weaknesses. It's up to us to learn what those are so we could use it properly. Many times people are just disappointed because it doesn't perform well in extreme conditions.
















PostPosted: Tue Dec 06, 2022 6:26 pm    Post subject: Reply with quote
Indigo82 wrote:
All photos except close up macro shots are made at f1.2. It was Pentax K-1 full frame camera as mentioned in my first post.

Some more photos all at f1.2 except close up macro that is at f5.6.

It's not quite easy to photograph a moving swan at f1.2 by focusing manually.

Anyhow, I just wanted to say in this post that every lens has it's strengths and weaknesses. It's up to us to learn what those are so we could use it properly. Many times people are just disappointed because it doesn't perform well in extreme conditions.



These are all fantastic pictures!
I know it was not easy to photograph moving swan ... that I have learned, just did not learn yet how to successfully photograph moving swan with mf at 1.2 Smile.
But I hope I will get some lucky shots in the future as long as I practice Smile
These photos at 1.2, they are all of course edit in post processing. Are some of them cropped perhaps? For example, I wonder about the picture with blond girl in beige jacket. Lower right corner has almost no sharpness fall off, and in all my pictures shot with 1.2 there is significant sharpness fall off and some other things occurring in extreme corners?


PostPosted: Thu Dec 08, 2022 1:09 am    Post subject: Reply with quote
I have been out today, practicing again.
Below some pictures, but this time after edit in Capture One.
It might be that I over edited some of them.
I would appreciate any feedback....

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PostPosted: Thu Dec 08, 2022 10:16 am    Post subject: Reply with quote
Great, you're already getting to know your lens and the your work is much much better than sample photos in the first post. Why do people always post snapshots to describe a lens? Smile I must admit that I also make so many snapshots while testing a new (old) lens. Btw, I understand your language Smile
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