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Forum: Pentax SLR Lens Discussion 12-23-2021, 03:58 AM  
Birthday lens :D
Posted By Bui
Replies: 44
Views: 1,545
Your lens collection is a lot similar to me (small DA limited + small compact telephoto zoom), they are my main go-to for travelling, hiking and everyday shooting. I think adding a 55* or 70 is no rainer, I owned both in the past, but like the 70 better because it fits better the ďcompact and nice handlingĒ preference, being a limited. The rendering is slightly better in my eyes, and itís much lighter, so unless you need 1.4 or WR I would go for a HD 70.

On top of these main lenses I have a few other that might trigger your potential interest for your next lens:

- DFA 100 macro: for macro and short tele/portrait. Very sharp, compact and nice handling but I rarely use it

- DA* 11-18: for when I can afford to bring something bigger than the 15. I like wide angle and this lens is unbeatable bar size and weight: sharp, fast, silent focus, excellent build and handling, wr, fantastic color

- DA* 50-135: for traveling, portrait when I can afford to bring something bigger than the 55-300. Itís longer heavier and only 135 but itís 2.8, sharp and renders beautifully. The 55-300 canít touch it in their overlapping range.

- Sigma 70-200 (recently acquired) for indoor shooting of daughter at her performance (swimming , piano etc). This lens os is super heavy so it will only be used 2-3 times per year.

- DA* 200: I bought it because of a rare chance for an unbeatable price, but I have almost no use for it. It gives some marvelous portrait shots (2.8 at 200mm!!!) and sometimes I use it for hiking to shoot animals, adding a 1.4 TC. I donít want to sell it because of its wonderful images and great handling

In the meantime Iíve also swapped my DA 35+ 40 for an FA 43, and DA 70 for FA 77, for occasional speed need, and the increase in size and weight is negligible.

For my next lens I may add the new DA* 16-50 because I heard itís a great lens. At 1500 euros however, I can certainly wait for a few more months/ years.

Happy Holidays!
Forum: Pentax K-3 III 12-17-2021, 06:54 AM  
Pentax K3iii video performance?
Posted By Bui
Replies: 15
Views: 832
I finally decided that I'm still not ready yet for the K3iii. 2k is a lot, and the K3iii, while being a substantial upgrade over my Kp, is not exactly my camera profile (I want small and compact camera, never shoot action, etc), indeed I want a KPii.

While waiting for further research and maybe better opportunities, for a temporary upgrade over my kits, for indoor performance daughter photos, I've just purchased a Sigma 70-200 (OS HSM version), it can replace both my DA* for this activity, offering better image quality (the 50-135 is weak at 135, not to mention 135 is sometimes too short), and flexibility (over the 200). For video, I just bought a used Sony camcorder last night for 250e, I know it will be a good upgrade for me because it can zoom with continuous focus, and video quality looks better than my KP's output.

Thanks a lot for your advices and comments.
Forum: Pentax K-3 III 12-16-2021, 01:40 AM  
Pentax K3iii video performance?
Posted By Bui
Replies: 15
Views: 832
Right, I believe "compatible lenses" here mean PLM lenses, I do have the 55-300 PLM however it's too slow for what I want to video (indoor sport and performance) so I'm stuck with either the old DA* 50-135 or the DA* 200, neither of them can autofocus with my KP during video.

---------- Post added 12-16-21 at 01:42 AM ----------



Thanks, it is a good solution, however not exactly applicable in where I live (very few options, and they're not exactly close). I also tend to want to own my equipments than rent, not very rational of course:lol:

---------- Post added 12-16-21 at 01:46 AM ----------



Sounds like a real improvement, as I found the video quality of my KP and 50-135 combo is so-so (of course taking into account less than ideal condition, plus my limited video skill). Missing continuous AF, however, is bothering ...

---------- Post added 12-16-21 at 01:54 AM ----------



Thank you, very useful comment. The Panasonic S5 looks nice, but with its price being close to the K3iii, I will go for the later if I decide to invest.
Forum: Pentax K-3 III 12-12-2021, 02:25 PM  
Pentax K3iii video performance?
Posted By Bui
Replies: 15
Views: 832
I know it's no point buying a Pentax camera for video, but I now want better video performance (technically) from my current equipment: a Pentax KP + a 50-135, a 55-300 PLM, and a few DA/FA limiteds. Aside from taking photos as I have always been doing, this year there has been a new need: I want to record daughter's performance: indoor swimming, year-end piano club, etc). The current gears are very good for still photos, but for video there are a few problems: so-so video quality, non-autofocus during the process (very annoying), and average anti-shake performance. Better than the wife's iPhone, but no more.

Do you think the K3iii offers a (much?) better video performance? I like the camera but have been happy enough with the KP so that I am still not ready to pay 2000e for a new camera. An actual upgrade over video, however, might seal the deal.

Or I'm thinking about the possibility of buying a non-Pentax camera which is supposed to be better than Pentax in term of video (Sony, Fuji etc) but I don't really want to maintain 2 different systems. Too expensive!

Or do you know a special list video camera that preferably has decent zoom range, quality, and not overly expensive?

Thank you.
Forum: Pentax SLR Lens Discussion 10-27-2021, 03:26 AM  
Upgrade 12-24 to 11-18?
Posted By Bui
Replies: 45
Views: 3,757
Taking the opportunity of being reminded about my own thread 1 year ago (thanks @UncleVanya), I would like to report that I actually pulled the trigger not long after opening this thread (LBA LBA :D), and sold the 12-24 shortly after. I apologise for not being able to provide comparisons photos, because first I'm very uncomfortable doing that work, and secondly to have infinity landscape with enough details to do comparison I have to drive out of the city. So here is my subjective "judgement":

11-18 +:
- It is sharper and crispier. It was down to my copies of course, but for sharpness I think no technical comparison is needed, if you see your photos on a large screen you will realise the 11-18 is sharper, especially at wide end
- Much better build quality. Not a limited type but the 11-18 is very well built, feel great in my hands, and also it's operation (focusing, zooming, etc). This feeling when using a lens does not contribute directly to image quality, but it has quite an impact on my motivation to take photos, personally
- Adding to good handling is silent focusing
- Internal zoom. It's not technically internal zoom, but it looks like an internal zoom lens (the front elements movement is very shoot, and only inside the outer of the lens
- WR. I think for a landscape lens WR is an important feature.
- Wider. 11mm is wider than 12mm
- Very good flare-resistance for such a zoom
- Could be use with FF from like 16-18mm. Even at 15mm with significant vignetting I still prefer this lens to the Irix 15mm which I had at the time. I eventually sold both the Irix and my K1-ii so this no longer applies.

11-18 -:
- An used 11-18 is still at least 2 times more expensive than a 12-24
- It is heavy, really heavy, and
- It is big big, and its hood is ridiculously large. It takes a lot of spaces in my bag, and in fact for a trip it eats up the space of at least 2 other random lenses than I could usually bring
- Limited zoom range: it's not possible to leave this lens as a default lens on my camera, due to 18mm being too wide for the better part of my shoots. 24mm could do otherwise
- My cameras are the KP and KS-1, with both of them the lens makes the combination very front-heavy, quite clunky to carry

12-24? Basically the reversal of above points:
- It is lighter, smaller, and cheaper. I do miss its size
- In exchange, build quality is nothing to rave about
- 12-24 = starting to enter normal range territory, so it can be used as a default lens
- Sharpness is a bit inferior to the 11-18, but I feel the color is as good
- I don't remember it's flare resistance ability

Conclusion is already known: ideally you should have both, with the 11-18 for more serious shooting, long trips, rain, etc, while the 12-24 for more casual ones. If wide-angle photography is just a complementary part of your habit, you can live perfectly fine with the 12-24, however if you take a lot of wide-angle photos, eventually you would upgrade to the 11-18, that's inevitable.
Forum: Pentax SLR Lens Discussion 06-17-2021, 12:27 AM  
Limited kits: 15 - 20-40 - 70 or 15 - 21 - 40 - 70?
Posted By Bui
Replies: 48
Views: 2,347
To me the 20-40 is a perfect compromise between flexibility and quality (that is if there is any compromise). In the past I own the 21, 40, 16-85, 18-135 and 16-50 together with the 20-40, however I eventually sold all of them but the 20-40, now most of the time I only use the 15, 20-40, 77 trio. I might not appreciate the 21 enough but I think the only advantage it has over the 20-40 is size, and star burst (for the SMC version). The 40 has more distinct quality to the 20-40 (substantially smaller and faster, a bit sharper) but 40mm is a bit odd focal length to me in APSC.

Conclusion: get the 20-40, eventually you will also get the 21 and 40, and then you will decide for your self.
Forum: Pentax SLR Lens Discussion 04-27-2021, 05:00 AM  
Pentax 43mm f1.9, is it worth it?
Posted By Bui
Replies: 51
Views: 3,303
If in doubt, I would buy it, try it, and keep it if I like, sell it if I don't. It's better to try than never be sure.

Beside that half-joke, do you want f1.9?
Forum: Pentax SLR Lens Discussion 03-29-2021, 11:26 PM  
What were the last 2 lens you purchased and why?
Posted By Bui
Replies: 84
Views: 4,660
Iím very curious about the A28/2, there is very little information about it. What do you think of it? Is it worth pursuing one?
Forum: Pentax DSLR Discussion 12-15-2020, 03:44 AM  
To buy or not to buy the Pentax 28-105, or the question of walking-around with a K1
Posted By Bui
Replies: 38
Views: 2,848
Thank you for advice. In fact except for some D-FA* lenses who are either too big, too expensive or both, I prefer high quality and automation lenses for travel convenience and I'm willing to pay for them, hence even my A28/2 for example, is great, I rarely use it but rather my modern 20-40 and DA 35ltd.

---------- Post added 12-15-20 at 03:48 AM ----------



Very useful advice. I don't plan to get rid of the APSC system at all, maybe selling a few lenses if I use their FF equivalences more. I look forward to experiencing the K1 perspective, and I will targeting a 31 and a 43 soon.
Forum: Pentax DSLR Discussion 12-15-2020, 01:55 AM  
To buy or not to buy the Pentax 28-105, or the question of walking-around with a K1
Posted By Bui
Replies: 38
Views: 2,848
Wow lots of replies, thank you!



How do you feel the # between K3ii + 16-85 and K1ii + 28-105? I mean looking at them as a combination, rather than an individual contest between the 2 lenses. For landscape, for example,

---------- Post added 12-15-20 at 01:59 AM ----------



I understood that you meant better image quality from the FF combo? The 16-85 to me is the best general standard lens for a crop camera, and I'm sure the 28-105 is too, for a K1. My question is rather, "I have a KP with 16-85 mounted and a K1, should I buy a good all-around lens for my K1, or it's already well covered with my KP"?

---------- Post added 12-15-20 at 02:07 AM ----------



Thank you, this is what I'm curious about. I decided to go for the K1ii very quickly without really thinking about future, since the price was so good, but now I realise there could be a lot of duplication, and a relatively waste (or not optimal) use of my APSC equipments, if I'm happy with the K1 and can live with the extra weight. Bringing 2 cameras at once is not yet a consideration for me at this point.
Forum: Pentax DSLR Discussion 12-14-2020, 01:58 PM  
To buy or not to buy the Pentax 28-105, or the question of walking-around with a K1
Posted By Bui
Replies: 38
Views: 2,848
So, I have just bought a K1ii. Do I need it? I don't think so, having been happy with a KP and a decent set of DA Limiteds + a few others DA* and so on. Do I want it? Absolutely, I'm always curious what FF looks like, and I also want to try a K1 with the 31-43-77 trio to see what all the fuss is about. Why did I buy it? Because I saw a used K1ii at an unbeatable price, and also because I have decided that the K3iii is not what I want.

In terms of lenses, I have the DA* 11-18 which you (the forum) say works in FF from 15mm. I also have the legacy A28/2, the DA* 55, the 77, and the macro 100, so I'm good. As we're heading to Christmas vacation in the mountain (after 1 month and a half under lock-down in France), we're raring to go, and of course I look forward to having new experience with my new camera. But I rarely travel without at least 1 general and WR lens (for example for the KP it would be the 16-85). So I'm looking at the 28-105. I did some research, found a few discussion in the forum, and it seems the conclusion is, it's a very good lens, and "an equivalent of the 16-85 on APSC". Wait, what? So then why should I buy this lens to walk-around a 1.5 kilograms package, to have similar quality (and even less flexibility) to the 1.2 kilograms KP + 16-85?

Or the question is, for someone owning both Pentax FF and APSC system, you buy the 28-105 because image quality of the FF combo is better (resolution, noise, etc), or because you don't want to bring 2 cameras?
Forum: Pentax SLR Lens Discussion 11-05-2020, 05:58 AM  
What do I gain, going from KP/K3iii+DA 16-50 to K1ii+DFA 24-70?
Posted By Bui
Replies: 36
Views: 2,548
It is really a problem. I currently own all DA limiteds: 15-21-35-40 in SMC and 70-20/40 in HD. I never try any of the FA's. I purchased a 43 from a forum member last month but it was a sad story, the lens got lost during the long way shipping from the US to Europe. That's said, the FAs are much more expensive than the DAs, so having some of all of them would not be that straightforward, and most likely I will have to sell some of mine currently.
Forum: Pentax SLR Lens Discussion 11-05-2020, 04:03 AM  
What do I gain, going from KP/K3iii+DA 16-50 to K1ii+DFA 24-70?
Posted By Bui
Replies: 36
Views: 2,548
Thank you for your comments, I think I've made up my mind. I will hunt down ideally an used K1ii, starting from a few FF primes I currently have, getting a 24-70/28-105 as next step, and see when I can put my hands on the 3 Amigos. That way I will be experiencing something new: full frame. It may or it may not fit with me, but I'm not afraid of selling things that don't work with me. The KP will stay with me in any case, for when I want portability. Both K1ii and K3iii does not hold a candle to it in this regards, and considering the K3iii's improvements do not mean a lot to me, I will wait for it's review, reduced price, or ideally a KPii.
Forum: Pentax SLR Lens Discussion 10-29-2020, 03:38 AM  
What do I gain, going from KP/K3iii+DA 16-50 to K1ii+DFA 24-70?
Posted By Bui
Replies: 36
Views: 2,548
That's a great sum up, though I would assume a few of them are applicable for the K3iii. It's really a toss up.

---------- Post added 10-29-20 at 03:40 AM ----------



I think he meant other technology e.g. image processing, AF algorithm and tracking, etc. To me when I have to sacrifice weight I want IQ, so IQ technology will be of most important. In this sense if the K3iii is not expected to surpass the K1ii (High ISO, dynamic range), then K1ii is a no brainer

---------- Post added 10-29-20 at 03:43 AM ----------



This is interesting. I know the possibilities for trying new things with FF, shallower portrait for example, but landscape is still what I do most, and I'm not clear if FF makes a difference. But as you said, it's noticeably better.
Forum: Pentax SLR Lens Discussion 10-28-2020, 02:32 AM  
What do I gain, going from KP/K3iii+DA 16-50 to K1ii+DFA 24-70?
Posted By Bui
Replies: 36
Views: 2,548
It's a good question. I do not shot action, and I do burst shooting like 1-2 times every year. The most "action" shots I do is my daughter running in the forest, or a moving deer. Frankly, I have to admit, I don't really need to move on from the KP, it's good for me most of the time, and the fact that I went for it instead of the K3ii, was because of its form factor, and the non-requirement in fast action. The K3iii is not super attractive to me, if it were a KPii instead I would jump in immediately. If I upgrade, and it's not a KP type, meaning I will have to sacrifice compactness and portability, then I want the best IQ possible, that's why the K1/K1ii is looking nice, and especially with expected price of K3iii at 2000 euros (I can get a K1ii used at much less than that).

---------- Post added 10-28-20 at 02:36 AM ----------



Thank you for jumping in. The 24-70 is just a reference, because comparing (more or less) equivalent scenarios is easier, hence K1ii+24-70, since I use KP+16-50 quite a lot. If I ever get a K1, I know I will eventually get FA limiteds to try them on their home, for example. But it will be expensive, and for the time being, the KP with my APSC lenses are fine. On the other hand, most of the people who switched to FF say they don't use their K3/KP (a lot) anymore. So I'm quite curious.
Forum: Pentax SLR Lens Discussion 10-27-2020, 07:10 AM  
What do I gain, going from KP/K3iii+DA 16-50 to K1ii+DFA 24-70?
Posted By Bui
Replies: 36
Views: 2,548
I'm sorry if the question does not make sense, or it has been asked 9999 times in the forum, but it's still not clear at all to me.

Context: I have a bunch of DA Limited and DA* lenses, using it with a KP I bought used 3 years ago. The KP is excellent, but (but but but) when new shiny thing arrives, one can't help but start staring at it. Let's just say I want even better dynamic range and iso performance, better autofocus too, while more resolution does not harm. That's why I have been saving and preparing a bit of fund to invest in a new camera next year. Obvious candidate is the K3iii, but since the price would be >2000 euros, a K1/K1ii is increasingly attractive even if I am never really serious with moving to FF. After all I love trying new things.

I like landscape photography, and occasional portrait.

The cons of going for the K1 rather than K3iii, to me:

- Weight and size. Portability.
- Cost of future lenses. I have a few good FF or FF-ready primes so I have time

What about the pros? I like the KP+16-50 a lot, so I could imagine to go for the K1/24-70 combo if I go that route, because the price is quite good, but does that really make a difference?
Forum: Pentax SLR Lens Discussion 09-10-2020, 11:40 PM  
Upgrade 12-24 to 11-18?
Posted By Bui
Replies: 45
Views: 3,757
No not yet it will arrive next week. Will see if I have time to do such comparison. Never done such before.
Forum: Pentax SLR Lens Discussion 09-10-2020, 06:42 AM  
Upgrade 12-24 to 11-18?
Posted By Bui
Replies: 45
Views: 3,757
So, if you have to choose between your wife, and a lens, which lens would you choose?

I found a great deal of a brand new 11-18, couldn't help my self but clicking the "Pay" button. There is nothing wrong with my 12-24 and 14 but the temptation is hard. At least I'm confident I can resell the lens if it doesn't fit my expectation, though I think it's unlikely.
Forum: Pentax SLR Lens Discussion 09-03-2020, 07:47 AM  
Upgrade 12-24 to 11-18?
Posted By Bui
Replies: 45
Views: 3,757
The rent before splashing money is a good idea but it's difficult to rent Pentax equipments where I live. Usually I counter that by only buy used lenses at good price, so if I don't like them I can resell later at similar price, so no loss. If I ever get the 11-18, surely the 12-24 will have to go, but the 14 is a hard case, I quite like its images, even better than the 15, though the 15 will also stay due to its limited advantage. Also I have to be careful because since the COVID I have observed a big drop in used Pentax gears price.

---------- Post added 09-03-20 at 07:49 AM ----------



It was a joke, but yeah sometimes I feel a bit guilty after purchasing a lens, thinking that money could be spent for something else for my family. That doesn't stop me from acquiring a lot of overlapping lenses though.

---------- Post added 09-03-20 at 07:55 AM ----------



This, to tell you the truth I like the photos from K1+15-30 people post on this forum a lot. I know there are a lot of skills and such, but even technically, the sharpness, clarity, contrast and colour are obvious to see. I want those from my photos. Since I'm not going to FF anytime soon, if the 11-18 can be comparable with the 15-30 optically (I have a KP which is a baby-K1), it might be a good investment. The 12-24 is actually a very good lens, very sharp and versatile, but for some reasons I found the images a bit lacking, be it colour or contrast I can't explain, I just like photos from the 14 a bit more.

---------- Post added 09-03-20 at 07:57 AM ----------



Thank you, aside from flare resistance, do find improvement in other areas when it comes to image quality?

---------- Post added 09-03-20 at 07:58 AM ----------



Thank you, aside from flare resistance, do find improvement in other areas when it comes to image quality?

---------- Post added 09-03-20 at 08:46 AM ----------

How does Pentax's warranty work by the way? The question sound silly, but fact is I have never bought anything brand new from Pentax, if I go for this lens it will be likely my very first new purchase. If I have trouble with the lens, or if it has issues, like decentering, etc, would Pentax support?
Forum: Pentax SLR Lens Discussion 09-02-2020, 06:59 AM  
Upgrade 12-24 to 11-18?
Posted By Bui
Replies: 45
Views: 3,757
You call it LBA, I call it "striving for better":lol: recently I have been becoming more and more interested in shooting wide angle, starting from the 15 Ltd for some occasional wide landscape or with the sun, then a quick grab of the 14 last autumn before our trip to Austria, because the 15 was dropped and became decentered. I have since then re bought the 15, for when I need compactness, and the 12-24, used too. This year it has been almost the 12-24 as my default lens, due to its versatility, being a zoom, and the fact that it can go to 24mm. COVID 19 has stopped us from air traveling, but driving instead, so compactness of the 15 is not needed.

Having said that, the new DA* 11-18 has been tempting me more and more because:

- AW: non of my wide angle lens is WR, which is sometimes annoying, every trip I have at least 1-2 rainy days.
- Build quality: the 12-24 is not bad, but its design and build quality is outdated, especially sitting next to Ltd or * lenses
- DC and f2.8 are nice.

But mostly I want more image quality. I kind of lazy when it comes to setting up a shot, partly because I travel with a toddler and a very impatient wife, so I want equipments that can deliver even with less ideal conditions (e.g. no tripod, not waiting for better light etc). the 12-24 is good, but for some reasons I find images from the 14 better. I wonder how much better image quality I can get from the 11-18, considering the same shooting conditions? It's quite hard to find a direct comparison of this lenses with others.

I decide not to move to FF, even if it's technically the best option, due to size/weight and cost.

The cons would be:
- Price. It can be soften somewhat by selling my 12-24, and street price has now lowered a bit, closer to 1000e mark. I won't sell the 15, and perhaps the 14 either, it's kind of an unique lens.
- Bulkiness. Looks like its not much fatter than the 16-50, so not bad, but it will takes time to get used to a 700g default lens.
- My marriage. No, but seriously, having 3 wide angle lenses already that are working, why am I even thinking about this?

Your thoughts?
- Speaking of default lens, 18mm vs 24mm is a big difference, will be more lenses swap, unfortunately
Forum: Pentax SLR Lens Discussion 07-19-2020, 10:57 PM  
Pentax 20-40mm or Sigma 18-35mm
Posted By Bui
Replies: 28
Views: 2,644
Aside from the obvious differences in size, weight and speed, it depends on what you value regarding IQ. For example the 20-40 will be unlikely to be sharper than the Tamron 17-50 which youíre not happy with, but it gives much nicer images to my eyes. The Sigma is likely to edge the Pentax when it comes to sharpness, according to test, but the Pentax does not have autofocus issue, and handling is a joy. In term of rendering I can only say the Pentax is great, never use the Sigma.
Forum: Pentax SLR Lens Discussion 06-07-2020, 10:30 PM  
Light zoom for hiking
Posted By Bui
Replies: 13
Views: 1,130
To keep very high quality and maintaining flexibility at the same time it will be hard to keep the weight down. A KP + 18-135 is 250g lighter than a K3 + Sigma 17-50. Noticeable but not that big of a deal. I usually hike with my Kp and 16-85/16-50, and sometimes when we go to places we know already I substitute the zoom for a 21 and/or 40 the combo is very light and of course I lose flexibility.

Recently I bought an used K-01 for a very cheap price, and I plan to use it with the 18-50 retracted zoom. I think when it comes to Pentax ApsC this is the ultimate lightweight zoom package you can go for. In terms of image quality I will need to play with it a bit but I think it will be fine.
Forum: Pentax SLR Lens Discussion 05-26-2020, 02:44 AM  
Lens design question: what make a lens bigger/smaller?
Posted By Bui
Replies: 38
Views: 2,038
Thanks for your simple explanation. I have a few follow-up questions, if you don't mind :)

- Focal length = distance from the lens to the focal plane. From which point/part of the lens though?
- About registration distance, do you happen to know the registration distance of Pentax cameras?
- For a given focal length/registration distance, is this possible (in theory) to add unlimited number of elements, or there can be only a certain number of elements before the lens exceeds its own focal length?
- For a given focal length/aperture/design, what need to change, roughly, if for example, I want the Sigma to cover full frame sensor?



Sorry I did not mean the front element, but the size of the iris of each lens respectively, it's easily to see the iris/opening of the Sigma is much smaller than the Pentax, which is logical to me since it's almost 2 times shorter, having the same f1.4. What confuses me is the fact the the Sigma is fatter than the Pentax, even if it has smaller elements (in term of diameter).

My sideway question: I notice some lenses have big front element, but small iris. The Iris size is obviously respectable to it's aperture/focal length, but why the front element needs to be so much bigger? To gather light?



I think you're right, Sigma lenses, especially Art lenses are the ultra-corrected type in my perspective, they tend to have a lot of elements, hence very sharp but very heavy. I'm a fan of small and light lenses, hence the Sigma 30 is the only Sigma lens that "qualifies" in my book (considering it's a 1.4 metal internal focus motor lens) with acceptable size and weight and quite low number of elements to Sigma standard. The price to pay is purple fringing all over the place and less sharpness but I'm fine with that.
Forum: Pentax SLR Lens Discussion 05-18-2020, 08:19 AM  
Lens design question: what make a lens bigger/smaller?
Posted By Bui
Replies: 38
Views: 2,038
I'm bad at physics so don't laugh at me :lol: I just want to understand more my lenses from physical point of view. Here are my 2 fastest lenses: the recently acquired Pentax DA* 55mm 1.4 (on the left), and the Sigma Art 30mm 1.4 (on the right). Spec wise, they're quite similar: f1.4, 9 elements in 8 groups, has an internal motor (SDM/HSM), except for focal length of course.

My question is:

- Why the Pentax is just slightly longer than the Sigma, having almost 2 times the focal length?
- Why the Sigma is even bigger than the Pentax (the 2nd photo)? Since it's 30mm, to maintain the f1.4, its "opening" should be nearly 2 times smaller that the Pentax's, I can see in the photo, but why its overall size is still bigger? The Pentax is better optimized, or the SDM is small than HSM, or there is another reason?
Forum: Pentax SLR Lens Discussion 05-18-2020, 08:03 AM  
What is this fog-like looking on my lens?
Posted By Bui
Replies: 10
Views: 1,598
Finally I have time and manage to get rid of some laziness to open up my A28 f2 again. I have now the front elements part, which I can see the haze inside. The problem is I can't separate them, this part seems to go tightly together. Based on the diagram one of you posted above, no element is glued together, but here I find it very difficult to break them up. Any idea?
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