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02-18-2013, 02:18 AM   #1
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Fast cheap 28mm lens -- an impossible dream?

Just bought and am learning about my new K-01, and about APS-C photography. Coming to it from an Olympus XZ-1... with a much smaller sensor.

I enjoy low-light photography. But the camera gods giveth, and then taketh away, don't they? The XZ-1 has f/1.8 28mm equiv lens, but... because the sensor is small, you get a lot of noise over ISO 400. Then, there's the K-01. I can take a perfectly good picture at ISO 1600... but my 18-55 kit lens (27 - 85 equiv) starts at f/3.5 then goes to f/4.5 at 24mm (36 mm equiv) and so on.

So this got me looking -- and learning -- about Pentax lenses. Looking for a 28mm prime (42mm equiv) at f/1.8, or f/2. Well, forget that one! VERY expensive... like the 31mm (47mm equiv) f/1.8 Pentax sells for $1300. And that's dollars, not pesos, unfortunately. Wow!

Photography. There's no free lunch, is there? The bigger the film or sensor, the larger the lens to cover it, and then much more costly glass -- even more costly to stay up with new high-res sensors.

Side notes -- thought maybe I could stick Nikon lenses on the K-01. You can, sort of... old non-AI lenses will go on but not click into place. And you can get an optical adapter (with its own lens) for AI and newer lenses... but. The adapter lens adds a stop, or 1.5 stops, and you are back where you started.

But I am buying a $50 brass adapter to mount medium-format lenses. They are so sharp on my 645N... figure it's worth a try to see if they stay sharp on the K-01. Again, a big trade-off... a 2.6X crop factor... that 75mm yields a 195mm field-of-view on the K-01.

Solution? Write your Congressman. Instead of millions for lithium-ion batteries that light up Dreamliners, how about a national project to develop a $200 K-mount 28mm f/1.4 lens? Yes!!!

02-18-2013, 02:48 AM   #2
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QuoteOriginally posted by jon404 Quote
Just bought and am learning about my new K-01, and about APS-C photography. Coming to it from an Olympus XZ-1... with a much smaller sensor.

I enjoy low-light photography. But the camera gods giveth, and then taketh away, don't they? The XZ-1 has f/1.8 28mm equiv lens, but... because the sensor is small, you get a lot of noise over ISO 400. Then, there's the K-01. I can take a perfectly good picture at ISO 1600... but my 18-55 kit lens (27 - 85 equiv) starts at f/3.5 then goes to f/4.5 at 24mm (36 mm equiv) and so on.

So this got me looking -- and learning -- about Pentax lenses. Looking for a 28mm prime (42mm equiv) at f/1.8, or f/2. Well, forget that one! VERY expensive... like the 31mm (47mm equiv) f/1.8 Pentax sells for $1300. And that's dollars, not pesos, unfortunately. Wow!

Photography. There's no free lunch, is there? The bigger the film or sensor, the larger the lens to cover it, and then much more costly glass -- even more costly to stay up with new high-res sensors.

Side notes -- thought maybe I could stick Nikon lenses on the K-01. You can, sort of... old non-AI lenses will go on but not click into place. And you can get an optical adapter (with its own lens) for AI and newer lenses... but. The adapter lens adds a stop, or 1.5 stops, and you are back where you started.

But I am buying a $50 brass adapter to mount medium-format lenses. They are so sharp on my 645N... figure it's worth a try to see if they stay sharp on the K-01. Again, a big trade-off... a 2.6X crop factor... that 75mm yields a 195mm field-of-view on the K-01.

Solution? Write your Congressman. Instead of millions for lithium-ion batteries that light up Dreamliners, how about a national project to develop a $200 K-mount 28mm f/1.4 lens? Yes!!!
Have you tried looking for the K or A 28mm f2s? They seem to be quite rare but get excellent reviews in the lens database.
02-18-2013, 02:58 AM   #3
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There are Sigma 24 and 28mm f1.8s, and a 30mm f1.4.
02-18-2013, 04:23 AM   #4
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Hi jon404
I've just added a new thread which somewhat crosses over with yours...if you wanted to have a look...
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/215852-vivitar...us-series.html
Cheers
Dean

02-18-2013, 04:24 AM   #5
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QuoteOriginally posted by jon404 Quote
Solution? Write your Congressman. Instead of millions for lithium-ion batteries that light up Dreamliners, how about a national project to develop a $200 K-mount 28mm f/1.4 lens? Yes!!!
If Samyang can't make a fast wide angle for $200 while leaving out modern features like auto focus, what makes you think Pentax can?
Samyang 24mm f/1.4 ED AS UMC Wide-Angle Lens for Pentax SY24M-P

Little less wide at 35mm, but still f1.4 and way over $200.
Samyang 35mm f/1.4 Wide-Angle US UMC Aspherical Lens SY35M-P B&H
02-18-2013, 05:01 AM   #6
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If you want to go faster than 2.8 you more than likely will need to save your pennies, more than $200 anyway. You could get an older 28mm f2.8 for less than your price but probably be manual focus.

With the K-01 don't be afraid to bump up the ISO if needed, it will perform admirably.
02-18-2013, 05:30 AM   #7
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Yeah, with the K-01 you have two useful features: good high ISO performance (so you don't need really fast lenses, except if you are shooting in dark places) and focus peaking (which can be a useful tool to help with manual focusing)
If a lens is really fast, it needs to sacrifice some other things. AF, distortion, aberration, sharpness.. So getting a f2.8 or even a f3.5 lens is nothing terrible and usually means you can use it perfectly well wide open (with many super fast lenses, their performance wide open is not that great)

But yes, I am also surprised that 28mm lenses tend to not be very fast. 24mm and 35mm lenses tend to be faster (and have better IQ?), I guess the 28mm focal length just never was that popular for the lens manufacturers to put a lot of design effort into them. Maybe this will slowly change, with APS-C becoming so popular.
02-18-2013, 05:54 AM   #8
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The lens designer's dilemma...

Fast - Cheap - Good, pick two.

02-18-2013, 07:22 AM   #9
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QuoteOriginally posted by Na Horuk Quote
But yes, I am also surprised that 28mm lenses tend to not be very fast. 24mm and 35mm lenses tend to be faster (and have better IQ?), I guess the 28mm focal length just never was that popular for the lens manufacturers to put a lot of design effort into them. Maybe this will slowly change, with APS-C becoming so popular.
Whaaat? 28mm must be the most popular focal length for wide angles (old ones at least).
To the OP: What's wrong with the f/2.8 anyway? Seriously.

QuoteOriginally posted by boriscleto Quote
The lens designer's dilemma...
Fast - Cheap - Good, pick two.
That's a good one - it's old but never stops being funny.
02-18-2013, 08:53 AM   #10
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Well, you can find faster 28mm lenses on Ebay. Never bid on a 28mm by itself although I did pick up a 28mm 2.5 in a lot quite a while back.

Here is a Vivitar 28mm f2.0 that only has a day left. Bet it will probably go for less than 200. Only up to $30 right now.
Vivitar 28mm F2 Lens for Pentax PK F2 0 Wide | eBay

And there is also a Kiron 28mm f2 with a BIN price of $195
Pentax K Fit Kiron 28mm F2 Multi Coated Fast Wide Angle Lens | eBay
02-18-2013, 09:54 AM   #11
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If F2.5 is fast enough for you, then take a look at the Tamron Adaptall 28mm F2.5. It is a great little lens. I found one in "Ugly" condition for less than $2 and still is very sharp.

Here is the review Tamron Adaptall-2 28mm f/2.5 (02B) Lens Reviews - Tamron Adaptall Lenses - Pentax Lens Review Database
02-18-2013, 11:14 AM   #12
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Thanks all -- I'm getting an older 28mm f/2.8 manual, and, as you've said, it will do fine. This morning, learned the Focus Peaking and magnification with the e-dial in Manual Focus mode... absolutely amazing, you can't miss. Great camera!
02-18-2013, 12:00 PM   #13
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QuoteOriginally posted by jon404 Quote
Thanks all -- I'm getting an older 28mm f/2.8 manual, and, as you've said, it will do fine. This morning, learned the Focus Peaking and magnification with the e-dial in Manual Focus mode... absolutely amazing, you can't miss. Great camera!
For the small difference in cost, I recommend an A lens over full manual.
02-18-2013, 01:30 PM   #14
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For the particular specs you put forth, I would recommend the Sigma 28mm F1.8 EX DG. May not be in the sub $100 or less range, but for about $200 dollars I am happy with the results. It is a little on the big side though, or should I say not as compact as a Pentax prime. Otherwise go for a manual pentax K, M, or A and the Vivitar 28mm that many have recommended is also a great little 28mm.
02-18-2013, 02:23 PM   #15
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Hello

In that range of primes I have experiences with M28/2,8(MF) and Sigma 24/1,8 & 30/1,4.
All work well on the K01 - optically and speed the 30mm ist best (especialla in AL@3200ASA).
I like the 24 very much but on the K01 it is very bulky (Filter 77mm!!!)
For Street w/o using the screen he M28 might be good and it fits best from design point of view. (and I payed only about 25$ some years ago)

I analogue times wide angle lens an pentax had red number for apperture and distance - the combination of theese gave a good fix-focus combination... but I am acrais that this combination has only a more limited depth of field on Crop.
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