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12-04-2021, 09:23 AM   #1
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lens recommendation: Irix blackstone 15mm f2.4 vs pentax DFA 15-30 vs pentax DFA 21mm

Hello everyone! I'm looking for some recommendations. I'm thinking about purchasing a new wide angle lens but I would like some recommendations about which one is better for different types of situations and why. My current options are:

- Irix blackstone 15mm f2.4
- Pentax DFA 15-30 f2.8
- Pentax DFA 21mm f2.4 ltd

I haven't had any personal experience with any of these and considered any one of these because of the weather sealing. I'm taking a trip to ice land this winter and definitely need a wide angle for the trip. If any can attest to the weather sealing as well as how easy it it to catch focus in the Irix (MF) that would also be great.

Also if anyone has any experience with the new Pentax DFA 21mm vs the 15-30mm regarding use and AF it would be greatly appreciated. One of the things that puts me off of the 15-30 is its weight and size.

Thanks everyone!

12-04-2021, 09:36 AM   #2
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Yes, 15-30 does seem a bit overwhelming when you first use it. But after a few outings the size is less of an issue and the quality and range of the lens start to win you over. The DFA 21 looks great and early reviews are encouraging.
12-04-2021, 11:17 AM - 1 Like   #3
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I've got the Irix 15 (and 11, too, for that matter) and the Pentax 15-30. I don't have the 21. The Irix wide-angle lenses have had some history of occasional decentering. I haven't had that problem, myself, but you wouldn't want to be in Iceland, give the lens a little bump and find it then less than usable. The Pentax 15-30 is a wonderful lens, and will give you more flexibility in controlling the viewing angle in your compositions. I'd go with that one. Both are pretty well weather sealed, by the way, I've used both in the rain with no problems.

If the weight and size represent a significant issue for you, I wonder if you'd rather take a KP, K-70 or K3 with the DA* 11-18mm F2.8, which is also a wonderful lens.
12-04-2021, 02:30 PM   #4
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Let's talk focal lengths. A 15 is very different from a 21. If you've often used 15mm perspective in your photography, or if you really want to try, you won't be satisfied with a mere 21. Now look at the next longest lens you have. Does it start at 24, a 28, or more? The Irix 15 will leave you with a huge gap in coverage... unless you're comfortable cropping 1.5x in your K-1 (I am).

Generally I avoid F2.8 zooms. They're bigger and costlier than I want, while also being slower than primes. I see them as the Photojournalist's Compromise, jacks of all trades, but masters of none.

12-04-2021, 02:39 PM   #5
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I presume you are talking about a FF camera? There are better options on APS-C.

Of the three mentioned, I only have the DFA 15-30, and it is stellar. The only drawbacks are some rather attractive rainbow flaring when sunlight directly hits the bulbous front element from the side, and its physical width. It is an awkward lens to pack. For others, the lack of filter thread is an issue, but that doesn't concern me.
12-04-2021, 08:46 PM   #6
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QuoteOriginally posted by Mikesul Quote
Yes, 15-30 does seem a bit overwhelming when you first use it. But after a few outings the size is less of an issue and the quality and range of the lens start to win you over. The DFA 21 looks great and early reviews are encouraging.
Yeah its just carrying more than 2 lenses with the k1 makes your pack heavy real quick. I have a few day of ice caves planned so it makes me think twice.

---------- Post added 12-04-21 at 08:49 PM ----------

QuoteOriginally posted by dlhawes Quote
I've got the Irix 15 (and 11, too, for that matter) and the Pentax 15-30. I don't have the 21. The Irix wide-angle lenses have had some history of occasional decentering. I haven't had that problem, myself, but you wouldn't want to be in Iceland, give the lens a little bump and find it then less than usable. The Pentax 15-30 is a wonderful lens, and will give you more flexibility in controlling the viewing angle in your compositions. I'd go with that one. Both are pretty well weather sealed, by the way, I've used both in the rain with no problems.

If the weight and size represent a significant issue for you, I wonder if you'd rather take a KP, K-70 or K3 with the DA* 11-18mm F2.8, which is also a wonderful lens.
I currently have a k1. I used to have a K3 but sold it after getting my K1. I found that I just wasn't using my K3 and preferred the IQ of the k1 in all aspects even cropped. Going back to an aps-c isnt really a choice for me. The K1 has ruined all other pentax cameras for me hahah

---------- Post added 12-04-21 at 08:57 PM ----------

QuoteOriginally posted by Wheatridger Quote
Let's talk focal lengths. A 15 is very different from a 21. If you've often used 15mm perspective in your photography, or if you really want to try, you won't be satisfied with a mere 21. Now look at the next longest lens you have. Does it start at 24, a 28, or more? The Irix 15 will leave you with a huge gap in coverage... unless you're comfortable cropping 1.5x in your K-1 (I am).

Generally I avoid F2.8 zooms. They're bigger and costlier than I want, while also being slower than primes. I see them as the Photojournalist's Compromise, jacks of all trades, but masters of none.
I used to have the 20-40 limited and a rokinon 14mm. Unfortunately they were both for Asp-c so I wasn't a big fan of the vignette so I ended up getting rid of them. That being said I found the 20mm end of the 20-40 more than enough for what I wanted and never really needed to go a less than 20mm. I didnt find the difference as noticeable on the K1 vs using a k3. For me what Im considering is more what would be more convenient picture quality wise vs size. My big gripe with the 20-40 was that it wasn't particularly good at fast AF.

My other lenses are the pentax DFA* 50 f1.4 and the HD DA 55-300. I am really just missing a wide angle lens tbh. Im leaning towards the DFA 21mm f2.4 but I would be really let down if the AF system with that lens is as finicky as the DA20-40 ltd.

---------- Post added 12-04-21 at 09:01 PM ----------

QuoteOriginally posted by Paul the Sunman Quote
I presume you are talking about a FF camera? There are better options on APS-C.

Of the three mentioned, I only have the DFA 15-30, and it is stellar. The only drawbacks are some rather attractive rainbow flaring when sunlight directly hits the bulbous front element from the side, and its physical width. It is an awkward lens to pack. For others, the lack of filter thread is an issue, but that doesn't concern me.
Yes sorry I forgot to mention. I have the K1 which I will be taking with me. I used to have some aps-c lenses ( the DA 20-40 ltd and the rokinon 16mm f2) but I ultimately sold them because of the heavy vignetting and much less than perfect AF on the 20-40.

Have you tried taking you 15-30 along on long trips? what has that been like. And what solution did you find for filters?
12-04-2021, 09:50 PM - 1 Like   #7
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QuoteOriginally posted by dneira29 Quote
Have you tried taking you 15-30 along on long trips? what has that been like. And what solution did you find for filters?
Yes, the 15-30 has been with me to China, Cambodia, Japan, Czechia and Tenerife at least. It is absolutely sensational for temples, castles and especially interiors. I wouldn't be without it if I've taken my FF kit.

On the other hand, I may take the K3iii instead on the next trip (if there is to be such a thing), in which case the DA 15 Limited will be in charge of UWA duties. It's only 22mm equivalent though, so it doesn't really match up. Much easier to carry though. A tough decision.


Last edited by Paul the Sunman; 12-17-2021 at 11:12 PM.
12-05-2021, 01:27 AM   #8
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I have the Irix 15mm Blackstone (and also the 11mm like dlhawes). It's very good, very large and heeeaaavvyyy. It's a special lens, 15mm is very wide.
I'm planning on buying a D-FA 21mm when I can afford it (my savings up, the price down till they meet). I see it as at totally different lens, suitable for street and walk-around photography which the Irix isn't.

Kjell
12-05-2021, 02:43 AM   #9
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If you haven't seen it there are already a couple of user reviews for the DFA 21 Ltd: HD Pentax-D FA 21mm F2.4 ED Limited DC WR Reviews - D FA Prime Lenses - Pentax Lens Reviews & Lens Database

Unfortunately it all really depends a lot on your budget, if do you prefer primes or zooms, and how much weight you are prepared to carry around. I don't have a DFA 15-30 (I do a lot of walking and its a bit big / heavy for my use) but its certainly highly regarded in reviews. I have a DFA 21 Limited on order and will add a review once I eventually receive it ;-)
12-05-2021, 04:36 AM   #10
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For a trip like that the Pentax DFA 15-30 is the clear winner for it's flexibility of angle of view in a WR package (IMO) - it is bulky and quite weighty but will enable you to get more different angles (and there are quite few between 15mm and 30mm) of various locations.

You should consider whether you will be using filters or not, as that brings a whole new set of decisions
12-17-2021, 07:26 AM   #11
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Do you plan on using any filters? If I were going to a location I hadn't shot before, I'd want the flexibility that the 15-30 gives. The WonderPana FreeArc Core filter system is working well for me but that will add extra money, space, and weight. I know the DFA 21 has a nice and small 67mm filter but I'm not sure what issues you might run into with having the non-removable hood. If it were me going on the trip, I'd be packing my 15-30 and 28-150 and buying a DA 300 for the 3rd time.
12-17-2021, 08:01 PM   #12
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QuoteOriginally posted by jab2980 Quote
Do you plan on using any filters? If I were going to a location I hadn't shot before, I'd want the flexibility that the 15-30 gives. The WonderPana FreeArc Core filter system is working well for me but that will add extra money, space, and weight. I know the DFA 21 has a nice and small 67mm filter but I'm not sure what issues you might run into with having the non-removable hood. If it were me going on the trip, I'd be packing my 15-30 and 28-150 and buying a DA 300 for the 3rd time.
I would love to use filters but that might be just a bit out of the budget. Its quite an expensive piece to just able to use filters but I know adding one will be inevitable haha

---------- Post added 12-17-21 at 08:02 PM ----------

QuoteOriginally posted by kiwi_jono Quote
If you haven't seen it there are already a couple of user reviews for the DFA 21 Ltd: HD Pentax-D FA 21mm F2.4 ED Limited DC WR Reviews - D FA Prime Lenses - Pentax Lens Reviews & Lens Database

Unfortunately it all really depends a lot on your budget, if do you prefer primes or zooms, and how much weight you are prepared to carry around. I don't have a DFA 15-30 (I do a lot of walking and its a bit big / heavy for my use) but its certainly highly regarded in reviews. I have a DFA 21 Limited on order and will add a review once I eventually receive it ;-)
I would love for more reviews to be added. I feel that even though its a new lens more info should be out there already. I need a video review hahah
12-17-2021, 10:55 PM   #13
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QuoteOriginally posted by dneira29 Quote
I would love to use filters but that might be just a bit out of the budget. Its quite an expensive piece to just able to use filters but I know adding one will be inevitable haha

---------- Post added 12-17-21 at 08:02 PM ----------


I would love for more reviews to be added. I feel that even though its a new lens more info should be out there already. I need a video review hahah
I'd go for the 15-30. I personally wouldn't be happy with a 15mm prime on FF as it's generally too wide for me. The 21 will be nice but for your stated purpose you'll appreciate the flexibility of a zoom. Best wishes to you and I hope you have a wonderful trip!
12-19-2021, 09:44 AM - 1 Like   #14
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QuoteOriginally posted by jab2980 Quote
I'd go for the 15-30. I personally wouldn't be happy with a 15mm prime on FF as it's generally too wide for me. The 21 will be nice but for your stated purpose you'll appreciate the flexibility of a zoom. Best wishes to you and I hope you have a wonderful trip!
I keep finding myself inching towards the 15-30mm hahah. I really wish there was more information and user experiences with the new 21mm
12-19-2021, 08:25 PM   #15
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QuoteOriginally posted by dneira29 Quote
I keep finding myself inching towards the 15-30mm hahah. I really wish there was more information and user experiences with the new 21mm
Well I promise that if I win one in the giveaway I'll review the heck out of it
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