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Forum: Pentax SLR Lens Discussion 01-18-2008, 07:39 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
I have no opinion on that... ;) But, I think the picture is cool!

kindest,
Forum: Pentax SLR Lens Discussion 01-18-2008, 06:20 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
Aber natürlich!
We live in the times of oversharpening anyway. Besides of the megapixel race there is a freak'n resolution race going on, on the lens side. That serves us with axial CA and bright rings and harsh rendering.

blende8, is that avatar you?

regards,
Forum: Pentax SLR Lens Discussion 01-18-2008, 06:16 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
In reply #87 I mentioned that a filter just in front of the lens won't work. I also said that I don't know why it works when the extra set of aperture blades are placed closer to the standard aperture blades.

That was intuition. I don't know more about optics than a five year old kid playing with a magnifying glass in the sun.

My guess: Imagine a simple lens with two elements and an aperture mechanism in the middle somewhere, the lens focused to infinity.
Just in front of the front element we have the filter threads. Aim the lens towards the sun and we have the sun in focus at one extreme and the imagener at the other. By stopping the lens down, from, say wide open and one stop, we close the aperture rings a bit. This is done somewhere where we have "no focus" optically. We just lessen the light by stopping rays coming from the sun hitter the outer parts of the front element. The net result is that the picture gets darker.
Now the tricky part. The STF set of aperture blades makes two things: it darkens the picture, just as the ordinary aperture, and it has an pleasing effect on the OOF parts of the picture by smoothening them. My guess is that the STF aperture blades are placed pretty close to the standard ones but still at a "plane" where we have a little more focus, sort of speaking. I think you can understand how I am thinking, but I have of course no grip of this.

It would be fun to try something with a short tele lens with some air inside it between the lens groups. I'm thinking of a way to add apertures (cut out from paper possibly) in different sizes and move them a little forth and back to see what happens.
Maybe this is why the STF lens is a tele lens; they might have needed space in there to get a good aperture mechanism fit. I would like to have a FF sensor and a 24mm, a 50mm and a 90mm STF lens to go with it...

regards,
Forum: Pentax SLR Lens Discussion 01-18-2008, 05:56 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
I enjoyed. Thank you for the links! The flower shot is pretty promising. Now we have the question: Why don't Pentax or Sony or anyone more STF lenses, and in shorter focal lengths?
Forum: Pentax SLR Lens Discussion 01-18-2008, 05:54 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
Hi,

Yes, they are both sporting aspherical elements. The concentric circles are more pronounced with the Sigma lens, very faint with the Pentax. And sure, the second image is more "eyecandy" than the Sigma (the top one).

The good thing with the Sigma is that the bokeh is neutral where the FA35 shows bright rings. Thin smaller bright spots in the background and the Sigma will make make much better than the Pentax in this case. Then again, when these bright spots are near the edges/corners they get a weird shape with the Sigma, and much less (and softer) with the FA35.

What are the designers thinking of? :)
Forum: Pentax SLR Lens Discussion 01-15-2008, 02:48 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
"missing image file" I'm highly disappointed!
(And it took 2 weeks, a lot of vitamins and in the end two extra shifts at work to get back to the normal semi normal state of mine. I hope your weekends were a more pleasing experience!)

regards,
Forum: Pentax SLR Lens Discussion 01-15-2008, 02:45 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
I think you have "invented" the opposite of the filters used for fix vignetting (as with the Hasselblad Pan-X).

I'm not educated, nor an autodidact, when it comes to design anything optical. I'm happy by just using them... But my thoughts are that by placing something gradually in front of the lens it has a gradually visible effect. Think about these grad ND filters for landscape shooters.

I don't fully understand the details about why the Minolta 135mm STF lens works the way it does. I guess it has a lot to do with where the extra aperture is placed. Then again, sometimes one can get surprised so one should never say never... I have seen reports saying that placing a baffle (or an extra aperture opening between the lens and camera) can lessen flare from very fast primes. It sounds strange to me and the reports are a bit contradictory, as so often.

The extra set of aperture blades in the STF lens also closes the lens down, but with another effect than the ordinary aperture blades. The more a closed down, the lesser of bad effects from CA should be visible in the picture as the rays hitting the front element at it's outer areas are stopped. But that is basic, somewhere inside the lens all those rays of light are bent and diverted and I don't know what.

But the DIY stuff is interesting and if something can be done in this area I'm certainly interested.



Very interesting. I look forward to learn more about this!

Thank you,
Forum: Pentax SLR Lens Discussion 01-15-2008, 02:18 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
Hi mer (?),

I'm sorry for the late reply, I haven't checked back here until today.

I tried to describe how the word should be used in my opinion. The examples given works well, don't you think? My first language is Swedish, then I have a couple of third languages, all spoken badly, so I'm not the right person to discuss the these things in depth. If I'm describing the definition I think I'm content with that:

If the definition fits well, and the use of the word in the examples works fine I'm happy with that. I do realize I can't stop people saying things like "There is a lot of bokeh in that picture" but I can try.:)

If you think I am way off I can reconsider.

I haven't tried the DFA50/2.8 Macro. I like them fast, if possible. The plastic build also scares me. Not to mention the question about money...

The 125mm Voigtländer seems to be a great piece of glass and metal and I have seen many beautiful pictures taken with the lens. I have never tested it. 125mm is a bit long for me and I can't see myself hauling around that thing for occasional use.

kindest,
Forum: Pentax SLR Lens Discussion 01-15-2008, 02:10 AM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
creampuff, d.bradley and carpent;

Here are tow images showing small kitchy lamps once used for a freaked out party. it's the Sigma 30/1.4 and the FA35/2.



and



So, among everything revealed in these pictures it also shows us that aspherical elements are not alone responisble for the concentric circles sometimes seen in OOF bright spots.

I have seen the same thing in pictures taken with the Voigtländer SL 75/2.5.

regards,
Forum: Pentax SLR Lens Discussion 01-09-2008, 01:21 PM  
Bokeh, Specular Highlights, Guess The Lens - A Surprising Result
Posted By Jonas B
Replies: 113
Views: 25,074
Hi everybody!

I found my old password for the forum and can't resist jumping in.

Carpents mentioned this thread to me. I'm glad he did as I learned a few things from it.

Part 1:
Bokeh, or boke, is derived from Japanese and one of the stories about the word is about a certain style some Japanese painters used to paint fuzzy backgrounds in a manner reminding about the impressionism (you know Chagall and his water-lilies) and their way of just pressing the tip of the brush against the canvas. Those parts of the painting are not sharp but merely there to let the beholder emphasis on the sharp parts and at the same time make for a context.

That story suits me fine, it makes the word understandable. The spelling is not important. It started, in Englsih, as boke. The h was added pretty quickly as it helps with the pronounciation. I don't think there is "right" or "wrong" way to translate phonetic Japanese to English letters. Or maybe there is (I'm neither Japanese nor English -spoken)? Anyway, the most common way to spell bokeh is bokeh. The word is confusing as it is so why not use the most common way to spell it.

When using the word bokeh it replaces the whole phrase "quality of the out of focus parts of the picture". For example:

The bokeh is good = The quality of the out of focus parts of the picture is good.

or
What do you think about the bokeh? = What do you think about the quality of the out of focus parts of the picture?

Not like this:
There is a lot of bokeh in this picture = There is a lot of quality of the out of focus parts of the picture in this picture.

And not like this:
The DOF is thin, then the bokeh kicks in. = The DOF is thin, then the quality of the out of focus parts of the picture kicks in.

The last sample is from DPR which is a bad place. :p Don't repeat such things here... :)

From the above we can learn that "bokeh" isn't limited to the foreground or the background only. In general we think of the background as it is much more common with backgrounds than foregrounds. When choosing a lens I'm never interested in how it renders the OOF parts of the foreground. (Those that are have an excellent lens in the FA50/1.4.)

What about the bokehmania that hit the forums for a couple of years? Nothing special really. I think many want to use the word, many are seeking ways of expressing themselfs when taking pictures and a lot of experiments are going on now when we don't have to deal with chemical developing (and good photo editors are available). People communicate and pictures can easily be posted.

To me the real thing with the OOF areas are that I want them to just be there. They shall not make the beholder confused. They shall not make the beholder look at other things in the picture. They shall be soft and creamy and literally stick to the background helping the real content of the picture to reach the beholder.

When OOF highlights get green, or get bright rings, it can be distracting. When OOF stuff gets green (due to axial CA) it seldom enhances the picture. When OOF highlights are rendered with odd shapes due to the cat eye's effect it make the beholder to look at it and lose focus. Things going in and out to and from the focus plane should be rendered smoothly, in a way that doesn't keep the brain occupied trying to figure out what it is looking at.

In short; I want the OOF areas not to stand out.

This is valid for 99% or so of all pictures. The last 1% are pictures where the photogrpher seeks odd effects for the sake of it, as when the balls in the Christmas tree makes for funny blobs and such.

Part 2:

Lately the Sony/Minolta 135mm STF lens has been mentioned a lot. I want one. Just as carpents says; it's a reason to buy a Sony camera... that one, and the Zeiss/Minolta version of the 85/1.4.
If you have a 135mm STF collecting dust please let me know! If it is boring it is the right lens for me.

And another thing; I had some mail contact with a guy that has an STF lens fitting to a Nikon. Oh well... All sorts of things can be done. From the Nikon mount it isn't far to a Pentax mount. From either of them one can easily imagine an adapter and suddenly th lens fits a Canon, or an Olympus, as well...

Part 3:

There are a lot of new nicks here since I used to visit! Cool. I like this forum as it is reasonably moderated and free from ads. I enjoyed this thread. All the best to you all from me.

--
Jonas

(did you really read all this?)


and a random one:

E-510, Oly kit lens, my last picture of 2007, 1/45 of a second, Yeah! Fireworks... A few hours later it was mty head that exploded.
Forum: Sold Items 09-10-2007, 03:51 PM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
Sold and shipped.
Forum: Sold Items 09-02-2007, 01:43 PM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
As a response to the Headmasters request of cleaning the B&S forum:

The lens is stil for sale. Reply here and then PM me if interested. Make an offer.
Forum: Sold Items 08-17-2007, 02:55 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
No longer a reversed auction, sorry... The price is now what my BIN price will be when I eBay the lens later (this autumn).

I wish you all the best,
Forum: Sold Items 08-12-2007, 11:37 PM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
It seems low. I'm afraid you'll have to ask your friend to bring one for you.
Wow, I wish I had some friends like yours...

Cheers,
Forum: Sold Items 08-12-2007, 06:00 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
Maybe you should tell me why I should go quite a bit lower. How much is the lens where you live?

Here you can get an adjusted and nice copy, and even the exact lens that made the all time high resolution result at Photozone.

Of course, if there is a reason to go lower the price should drop a bit. Let me know why!

regards,
Forum: Sold Items 08-12-2007, 05:14 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
August 12, last call, last price reduction

A symbolic reduction of EUR 5, just done to bump the stuff.

This is the lowest the lens can go for this time. If there isn't anyone here interested in it I'll just keep it for a while and let it go somewhere else later.

regards,
Forum: Sold Items 08-11-2007, 06:25 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
Another EUR 10 down...
Forum: Pentax SLR Lens Discussion 08-10-2007, 03:30 PM  
Adapter to fit canon lens on pentax?
Posted By Jonas B
Replies: 7
Views: 44,587
Still, Canon and Olympus can use a lot more lenses than Pentax can. Their decisions about designing new lens mounts first made many upset but now they clearly benefit from it.

There is, unfortunately, no way to mount Zuiko OM, Leica-R and Contax (for example) lenses to Pentax cameras.
Forum: Pentax News and Rumors 08-09-2007, 08:44 AM  
Rumour
Posted By Jonas B
Replies: 41
Views: 10,357
Oh yeah. Now I can say the same thing. But why should one? Now there are always people liking rumours. I wonder what they do with it all?
Forum: Sold Items 08-09-2007, 05:09 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
Info and links added.

To celebrate the sell of the FA35/2 I lowered the price a further tiny step.

regards,
Forum: Sold Items 08-09-2007, 05:04 AM  
For Sale - Sold: FS: (EU) SMCP FA35/2.0 ED - reversed auction
Posted By Jonas B
Replies: 9
Views: 1,828
Sold and shipped
Forum: Pentax SLR Lens Discussion 08-08-2007, 04:30 PM  
31 Ltd. - my, oh my...
Posted By Jonas B
Replies: 12
Views: 1,657
Or perhaps with this one:


But now the OP says he likes the inbuilt hood... That makes him, the constructor and... well maybe one or two more.

The original hood didn't do it with 35mm film either. With the Sony sensor it gets plain stupid.

im(h)o,
Forum: Pentax SLR Lens Discussion 08-08-2007, 11:20 AM  
Pentax/Nikon/Canon - Sigma AF issues
Posted By Jonas B
Replies: 12
Views: 1,622
Forum: Pentax DSLR Discussion 08-08-2007, 09:22 AM  
something sliding within my new k10d
Posted By Jonas B
Replies: 11
Views: 1,908
I respectfully disagree and say that there should definitely be possible to hear and feel the sensor plate/suspension stuff move inside the camera. I can't see why there should be such an hugh amount of threads about it otherwise (here and at DPR). Then I'm not counting the OP more than once as he has cross-posted this question. I'll stop there though preventing me from going totally OT.

regards,
Forum: Sold Items 08-07-2007, 11:45 AM  
For Sale - Sold: FS: (EU) Sigma 30/1.4 EX DC KAF mount - reversed auction
Posted By Jonas B
Replies: 17
Views: 3,722
Ah, wth, to celebrate the sell of the K10D I just throw in another price drop, EUR 10 this time. How low will it go?
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