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08-26-2013, 01:05 AM   #1
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Difference in image quality : Pentax 18-5mm kit, Pentax 35mm f2.4 prime

I've been doing some serious testing of my 18-55mm kit lens and have discovered that at 40-55mm it's image quality is terrible, it's soft and horrible. I use my kit lens now from 18-35mm and no longer. I'm wondering, what kinf of image quality difference would there be bewteen the 18-55mm kit lens and the 35mm f2.4 prime lens?

08-26-2013, 01:18 AM   #2
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The DA 35/2.4 is much, much better ... the "plastic fantastic" that I use a lot because it shoots like a "50mm" on my K-5 ... and I still use the DA 18-55 WR as a short walk-around lens and for proxi-photo applications ... J

https://www.pentaxforums.com/forums/lens-clubs/196639-da35-f2-4-plastic-fantastic-club.html

https://www.pentaxforums.com/lensreviews/SMC-Pentax-DA-L-35mm-F2.4-AL.html#review5893
08-26-2013, 01:37 AM   #3
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QuoteOriginally posted by richardstringer Quote
I've been doing some serious testing of my 18-55mm kit lens and have discovered that at 40-55mm it's image quality is terrible, it's soft and horrible. I use my kit lens now from 18-35mm and no longer. I'm wondering, what kinf of image quality difference would there be bewteen the 18-55mm kit lens and the 35mm f2.4 prime lens?
A big difference, not least because you can use the DA35mm satisfactorily at f/2.4, two or three stops wider than a good result with the 18-55. I agree with you that the longest 10mm or so is the Achilles Heel of the 18-55, mine anyway. Mine is at its poorest at 55mm, at which point it is pretty bad, even stopped down. But in good light, if you want a bit of zoom flexibility together with light weight in that nice walk around range of 20-40mm or so, the 18-55 can be very useful, on holiday, say.
08-26-2013, 01:52 AM   #4
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The DA 35mm F2.4 is a great lens and as many others here I recommend it with all my heart.
See the link Jean Poitiers posted and I am sure it will convince you to buy one.
To me it's a great walk around lens and also works pretty good with portraits.

Cheers
Yos

08-26-2013, 03:00 AM   #5
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Well I don't earn much money so I have to pick a lens that's affordable but great. In a few days time i'm getting myself a new lens, i'm stuck between the Pentax 35mm f2.4 or the Tamron 90mm f2.8 prime. I just did some testing again on my 18-55mm kit lens and found that at f4-f6.3 the lens is pretty soft at 35mm, it's sharper at 47mm, horribly soft and poor image quality at 55mm, not bad at 18mm and not bad at 24mm. When I set the aperture to f8 sharpness improves but it's still not very good at 55mm and still sharper at 45'ish mm. So today i've been thinking about maybe using the 18mm, 24mm and 45mm focal lengths on my kit lens and moving backwards or forwards to compensate if I need to and buying myself the Tamrom 90mm f2.8, the reviews i've read on Photozone and ePhotozine said it's fantastic plus I read some user reviews on here that said it's amazingly sharp and overall excellent.

Do you think using the 18mm, 24mm and 45mm focal lengths on my kit lens and buying the 90mm Tamron would be a better idea than buying a Pentax 35mm f2.4? I do mainly landscapes of cities so 18mm, 24mm and 45mm would be ok for that but I also love doing close up photos of my kids as they play and also taking photos of them while they're sat daydreaming. I think photographing people daydreaming gets me wondering what they're thinking about, lol.

I do intend on buying a prime lens in the 35-50mm range but i've see the Sigma 50mm f2.8 EX Macro and supposedly it's better image quality than the Pentax 35mm f2.4. I was thinking right now, with my kit lens being ok at 18mm, 24mm and 45mm that a 90mm prime would be a sensible option.

Last edited by richardstringer; 08-26-2013 at 03:28 AM.
08-26-2013, 03:28 AM   #6
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I love my plastic fantastic 35mm 2.4. Images are sharp enough for me and so much lighter.
08-26-2013, 03:38 AM   #7
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I think i've decided, i'm gonna go for the Sigma 50mm f2.8 Macro in a few days time, and then a couple of weeks later i'll get myself the Tamron 90mm f2.8, then next month i'll get myself a Pentax 55-300mm zoom lens. I'm taking my two daughters to London the end of next month so I think the 90mm Tamron and 50mm Sigma will be great for the city.
08-26-2013, 08:32 AM   #8
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I've been pretty happy with with my kit lens results through the years although I'll admit that most of my shots are in the 35mm or under range and I use it mostly as a walk around/snapshot lens at times when lens swapping wouldn't be convenient. You might find that kit lens will be on your camera quite a bit on your trip as a 50, 90, and 55-300 zoom will be too long for the city. If the 18-55 isn't acceptable to you, then I would suggest replacing it with a better zoom such as the Tamron or Sigma 17-50/2.8 or some primes covering that range of focal lengths. The lenses you mention buying are all fine lenses but I think you will struggle with them in the city.

08-26-2013, 08:41 AM   #9
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You may just have a bad copy of the kit lens. I have the original version DA18-55, and still use it quite a bit. Stopped down to f/8 or so, I find the IQ at the 40-55 range to be ok. Not great, but certainly not horrible. As others have said, the DA35/2.4 is a very fine lens.
08-26-2013, 08:41 AM   #10
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Richard - have you thought about getting an older prime lens such as the A50 1.4 or 1.7? You can pick them up for very little but have to be happy with manual focus.
08-26-2013, 08:50 AM   #11
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As you're planning on buying the Tamron 90mm, I don't see the need for a Sigma 50/2.8 macro. For the price of the Sigma 50/2.8 macro, you can also (roughly) buy the DA35/2.4 and the DA50/1.8. I personally think that 35mm is more useful in the city.

I assume that you're aware that for architecture, an UWA (e.g. Sigma 10-20) is more or less a requirement; it depends on your expectations / style though.
08-26-2013, 08:52 AM   #12
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QuoteOriginally posted by thechumpen Quote
Richard - have you thought about getting an older prime lens such as the A50 1.4 or 1.7? You can pick them up for very little but have to be happy with manual focus.
Good advice, but for walking around the city I would have thought an M or K 28mm 3.5 would be even better. The 50s are great lenses but a bit tight for city purposes in my experience. It's a very personal thing though.
08-26-2013, 09:15 AM   #13
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QuoteOriginally posted by timo Quote
Good advice, but for walking around the city I would have thought an M or K 28mm 3.5 would be even better. The 50s are great lenses but a bit tight for city purposes in my experience. It's a very personal thing though.
I use a 28/3.5 Super Tak quite often. It's pretty easy to focus and stopped down it has very good DOF so I can pretty much shoot away. I also question whether the OP just doesn't have a bad copy of the 18-55.
08-26-2013, 12:04 PM   #14
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Richard, have you looked into a manual Sigma Macro 50mm f/2.8 for your macro itch? IMO it's extremely sharp and has saturated color. It can be had for around $100, leaving you room for the 35/2.4, which is wider and much more versatile with AF.
08-26-2013, 02:46 PM   #15
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Yeah I get what you're saying about the 50mm Sigma being tight and not giving me enough field of view in a city, I realised that only 4 hours ago when I set my 18-55mm kit lens to 50 mm (by taking a photo, looking on the lcd screen at what the exact focal length was, then adjusting the focal length a tad and taking another photo so I could get it to 50mm) and yeah it was tight, I very much doubt when I go to London next month that i'll be able to get far enough back in the museums to make decent use of the 50mm or maybe even the 35mm for that matter.

I've just about an hour ago read reviews of the Tamron 17-50mm f2.8, the reviews say it's an excellent lens and the image quality looks fantastic on the photos so i'm gonna be going for that one to use as a walkabout lens, it should be excellent in London when I go next month. Then just after I come back from London i'll buy myself a Pentax 55-300mm lens for wildlife. I went to a nature reserve today and the closest I could get to animals was about 50 metres away so my 18-55mm kit lens was useless really. I could crop the photos but the animals were so far away that cropped photos looked poor. Obviously also after London i'll get myself the Tamron 90mm prime lens for very high quality protraits of my kids. I want the highest quality lens I can afford for portraits because I intend to get a photo of me and my kids blown up to 30" x 20" scanvas to hang on my living room wall.

Last edited by richardstringer; 08-26-2013 at 03:18 PM.
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