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02-24-2015, 10:22 AM   #1
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Pentax-M 20mm f4 Help Me decide?

Good day my fellow Pentaxians,

Can you please help me make a decision regarding the purchase of a Pentax-M 20mm f4 which is being sold locally for a total of $310 CAN. The lens is in decent codition with some minor scuffs and paint loss. The elements apear to be clear (No fungus, coatings seem good, typical dust particles, no haze). The aperture blades seem to be shinny around the outer edges and I have been told by the person selling the lens that it is not oil but wear from use. The focus is smooth and the aperture ring is a bit loose, but functions as it is suppose to.

Most of my lenses are older and will hopefully fit a FF Pentax if it's ever produced (been waiting for years like others), with my only croped lens being the Tamron 17-50 f2.8. The Tamron is also the widest lens that I own and my second widest is the Pentax-A 35-105mm f3.5, so if I can actually afford the Pentex FF the widest lens that will fit the FF circle will be 35mm.

I really want to start getting into street photography and I love taking landscapes, so the light weight and size of this 20mm lens is very attractive for both. The biggest thing that is bugging me right now is that if I let it go will I ever get a chance to buy another one.

My decision is also hinging on the Pentax FF which may be a bad thing because it dosen't yet exist. There is also the Pentax-M 28 f2.8 which I am looking at because it is pretty much the same size and weight just not as wide.

Please help me!!!!!

02-24-2015, 10:33 AM   #2

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Well, the FF is definitely coming this year if you missed the announcement, but at what price?

310 CAN is about average for that lens so if it is in good shape it is not a fantastic deal, but it is a fair price. Once the FF does arrive, I'm sure you'd be able to resell it at about the same cost or a little more if you decide to.
02-24-2015, 10:37 AM   #3
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Traditionally street photography was done with 35mm on FF film cameras - often rangefinders. Sometimes it was wider, sometimes narrower. The challenge you have is that today the 20mm will act like a 30mm on your APSC camera which is likely pretty good from a street photography perspective. Later on FF this will be a much wider FOV acting a lot like the DA 15 does on an APSC body today - only wider. Some are happy to do Street Photography using a DA 15, but it differs from the norm significantly.

So you have a lens that will fit your needs today for Street Photography and morph into more of a landscape lens or unusual street perspective lens when used on FF..

I have no experience with this lens. I have used nothing wider than 24mm on Film Full Frame cameras other than very short focal length Fisheye lenses.
02-24-2015, 10:45 AM   #4
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I'm using this lens for this month's Single In challenge, and I've had it for about a year, bought in excellent++ condition from a PF user. You can go have a look at my Flickr site, and check my album for the M20/4 if you want some amateurish examples. I just looked at my aperture blades, and they're not shiny around the edges. This, plus the loose aperture ring is a red flag in my mind, so I'd be very cautious about purchasing this one.

02-24-2015, 12:44 PM   #5
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Back in the (FF) film era, 20 mm was my 'normal' lens, so I have 3 of these: 4.5 SMCTakumar screw mount, the 4.0 pentax-M, and the 2.8 FA autofocus. The M is wonderfully small and light, but I found myself carrying the extra weight of the FA because of the extra speed and the autofocus. The autofocus might be especially important for street work.
The price you mentioned seems a little high to me as I bought mine used in 1998 for about half that. Well, prices go up and this is not the most common lens. Don't however succumb to 'last chance' fears. In today's online market, you can find multiple examples of everything.
02-24-2015, 12:53 PM   #6
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QuoteOriginally posted by beagley Quote
Don't however succumb to 'last chance' fears. In today's online market, you can find multiple examples of everything
+1, it may be human nature to want to get in on a deal before it is no longer available, and in reality this rarely happens. There will always be another opportunity, but you will just not know when.
You can also use the 'Wanted' feature of the forum to ask for a specific lens if that's what you're after.
02-25-2015, 01:15 AM   #7

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I'm not familiar with the 20mm f4 lens. But i read you use a 17-50 2.8 on apsc. You should be able to deduct your favorite focal from that, no? At least from 28 onwards..
Personally, 20mm is a bit too wide for me to be a general lens. For street shooting i'd opt for a 24 or 28mm.

If any help. I actually like the m28 3.5. To me, it's sharper than the 28 2.8. It takes a bit less light, but if you'd buy sthing to shoot on FF later on...

QuoteOriginally posted by Ash Quote
There will always be another opportunity, but you will just not know when.
02-25-2015, 02:16 AM   #8
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I owned both the lenses till some time back but never at the same time - however as far as my experience goes, Tamron 17-50 is better than M20 f4 at all the apertures.

02-25-2015, 06:54 PM   #9
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If you are going to regret, buy and regret.
M series lenses have balsam exfoliation issue which happens on extreme thermal differences, ie: put the lense inside of your car for a while under strong sun light, balsam will melt and make some bubble in between the lenses and when its cool down, balsam will hardened with bubble still exist. However, M50/f2 is away from this issue which has no glue section in between the lenses.
before you buy, peek the lense against the strong light and check if there are any white scale or rainbow wave inside. If so, get an allowance and shoot some photo with film camera, since you mentioned about FF. Check your photo if it's acceptable or not.
It's all up to you buying or wave away, but if you are buying, prepare another couple hundred dollar to restore.
Estimated value of M20/f4 is around 40000 yen in Japan while ago, no matter what condition is, and increasing.
Do not miss the opportunity. It's worth paying! When you sell, just ask the same price you pay.
02-25-2015, 08:22 PM   #10
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I owned and loved the M 20 f4, but I only shot it on ap-sc digital.

It held up in every way to my DA 15ltd except for flare control - DA 15ltd was better there, a bit. M 20 f4 actually had better corners.

Very small, sharp, contrasty lens. I don't know if $310 CDN is a bargain, but it's in the ball park.
02-25-2015, 10:58 PM - 1 Like   #11

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I have never had any 'worn aperture blade' on my Pentax lenses (and I have quite a few), so I will advise caution on this purchase.
However, I've seen it on a few of my Russian lenses
Given the price, which is typical for the M20/4, I'd say look for a better one which is only worn in the external cosmetics.

I have this lens.
Its for FF and I've not used it on APS-C since 30mm eq FL is not what I can use often enough for a landscape lens over here.

Main advantage of this lens is that its really very small for a 20mm wide lens.
Its performance on a A7 (24mp with thick sensor stack ) is generally good at f8 with some softness on the last 1/10 of the frame.
By f11, the edges are ok, but the corners are still softish.
f16 improves the corners but there may be some diffraction, so f11 is the more logical setting.

Flare resistance is rather good, it can ghost, but not too bad on veiling flare. (esp considering its age and other 20mm of that era)

Coming back on that edge/corner sharpness thing, in real use, I have found it largely irrelevant.
1. Some distortion correction in PP trimmed off the edges and corners anyway
2. Any aspect ratio selection also trimmed off edges/corners.
3. Most compositions did not emphasize the corners and edges.

Most importantly, for me, its size and portability triumphed over other options available to me in my preference/choice.
And those other options are no slouches being the CV21/1.8 Ultron and Canon FD20/2.8.

taken with the M20/4

02-26-2015, 04:27 PM   #12
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Where is that first picture? That's beautiful.
02-27-2015, 07:13 PM   #13
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Thanks everyone for providing really good advise which helped me make my decision, which was to walk away form this one, but keep my eye open as I am still very much attracted to this particular lens. For now I am just going to enjoy shooting with what I have and start saving for the FF and maybe one day I will come across a really clean copy. And thank you pinholecam I really like the images you provided, I actually stumbled across the bottom two while searching for info on this lens and I thought they were pretty awesome.

Thanks again everyone and happy shooting
02-27-2015, 08:12 PM   #14

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QuoteOriginally posted by UncleVanya Quote
Where is that first picture? That's beautiful.

This is in Singapore.

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