[ehrwien]

I'm not used to the lingo because "wide open" means the lower numerical number correct?

That's correct, because the aperture number represents the result of a division: focal length divided by size of the physical aperture "hole" (diameter). That's why it's often written as f/2.8, for example, f meaning focal length. You can clearly see that if you keep the physical size of the aperture the same and make the focal length longer, the result of the division will get bigger. So in relation to the focal length the aperture size gets smaller, but the number gets bigger.
Wide open means the aperture is as big as it will get at a focal length for a lens, and the opposite of opening up an aperture is stopping it down.
For variable aperture zoom lenses, the aperture has a focal length range from which to which it will remain at the smallest number before stopping down a little. You can see about where those changes happen when putting the camera in Av or TAv mode, turning the zoom to the widest setting (smallest focal length) and opening up the aperture as far as it will go, and then turning the zoom ring to higher focal lengths. Watch the screen for the aperture number, and you will see it will jump up at certain focal lengths. As long as you do not stop the aperture down further, it will also open back up when zooming back out.

[VictorDA]

I did some portraits with it for my wife and while she thought the pictures were great, I wasn't impressed (the content was outstanding though). The quality just seemed meh.

My favorite lens(es) for portraits on APS-Cn when Q/P ratio is considered, were the manual 50mm: A- or M-series 50mm f/1.4 or 1.7.
Yes, they are manual focus. They are also plentiful and dirt cheap (for the quality) on the second hand market! expect to pay $30-100 depending on the version. Plus, MF forces the user to really think more about the shot and for me, I'm sure it was part of the appeal of the results.
So, my advice would be: before investing 100s in beautiful Limited primes (they are worh it, I'm not denying that), start with experimenting with something cheaper and get an idea of what you like or not. If AF is really not-negociable, why not the DA 50mm F/1.8? I never tried it but it can be found for $100 or below and reviews are more than enthusiastic!

[rogerstg]

What always confuses me is how aperture is talked about.

That's because it's being abbreviated in discussion. The number stated is the consequent of a ratio (like a denominator in division). Look at any of your lenses. For example, ƒ/2 is really the ratio of aperture to focal length 1:2. ƒ/4 is 1:4 and so on. It becomes easy to see that 1:2 is greater than 1:4, just like 1/2 is greater than 1/4. Once you understand that it's simply a ratio of aperture diameter to focal length, it becomes obvious that if the diameter is fixed, the ratio changes as focal length increases. ƒ/2 at 50mm becomes ƒ/4 at 100mm.

But what is really important is the effect on your photos. There's lots written on it, better and more comprehensive than I'm able to convey.

[shyrsio]

I wish I could be a prime shooter myself, but I find I always reach for the zoom most of the time. thats because usually I don't have a target of what I will shoot, but if you do, then prime is the way to go, I guess.

[sarge]

Maybe I should save up for the 16-50PLM...

I own this lens and it is worth every penny!
Another great option if you want a portrait lens is the DA* 55mm f/1.4.

[jgnfld]

Well now that I have the telephotos I have been wanting...it is time for something with a shorter range. I thought I would have been done lens shopping after my second telephoto but for some reason, I can't help but to look for something else!

Should I be focused on a prime or a zoom? I have the 18-135 that came with my K-70 but I would like a higher quality lens for less than 600 or so. I am thinking I would be using it mostly for portrait's around the farm. Close up's of the animals, my kids while playing with them or having the pose with equipment etc. The 2 cameras I would be pairing it up with would be the K-70 and KP (whenever it gets repaired)

Currently I have the DA 40 F2.8 xs, DA18-135, 55-300PLM, DFA 150-450 and Sigma 100-300 F4. I will most likely be selling the Sigma since I just got the 150-450 2 days ago for a good price. The 40mm is the only prime I have experience with. Does it even compare to more expensive primes? I did some portraits with it for my wife and while she thought the pictures were great, I wasn't impressed (the content was outstanding though). The quality just seemed meh. I used the KP while taking them and I'm sure there was a level of user error involved but I've done better with the 18-135.

I very much like the DA 40mm at golden hour or any other time the lighting is dramatic. It seems to render those situations wonderfully for me. For portraiture--even if it's your cow!!!--and for non-obscene pricing consider the relatively cheap (esp. when used) DA 70mm.

40mm



70mm



(Not a kid or a cow, but note the beautiful separation and creamy bokeh the 70mm gives.)


Can't recommend any of the wide angle primes, personally, as I don't own one. 'Course there are zoom options as well.

[aslyfox]

I'm going to suggest that the OP do some research

start by looking under " Articles " above

for example

Current K-Mount Zoom Lenses (2017)
Overview of Pentax and Third Party Zoom Lenses
By PF Staff in Gear Guides on Nov 21, 2017

Read more at: Current K-Mount Zoom Lenses (2017) - Gear Guides | PentaxForums.com

Current K-Mount Prime Lenses (2017)
Overview of Pentax and Third Party Prime Lenses
By PF Staff in Gear Guides on Nov 15, 2017

Read more at: Current K-Mount Prime Lenses (2017) - Gear Guides | PentaxForums.com

Manual Focus Lens Choices for Pentax
That old glass is amazing!
By K David in Articles and Tips on Jul 19, 2015

Read more at: Manual Focus Lens Choices for Pentax - Articles and Tips | PentaxForums.com

Beginner Portrait Lens Guide
What lenses to choose, and why- with a video demo!
By PF Staff in Gear Guides on Jun 11, 2013

Read more at: Beginner Portrait Lens Guide - Gear Guides | PentaxForums.com

look at the " in depth reviews " of lenses that are interesting

as well as the owners' reviews

_________________

a rule of thumb I was taught by my dad

zooms are compromises

compromises have limitations

now the newer zooms are much better than some developed for use with SLR

[dirwood]

Thanks for all the great info! I will check out those articles later tonight after the kids hit the sack.

[Alex645]

Should I be focused on a prime or a zoom? I have the 18-135 that came with my K-70 but I would like a higher quality lens for less than 600 or so. I am thinking I would be using it mostly for portrait's around the farm. Close up's of the animals, my kids while playing with them or having the pose with equipment etc. The 2 cameras I would be pairing it up with would be the K-70 and KP (whenever it gets repaired)

Currently I have the DA 40 F2.8 xs, DA18-135, 55-300PLM, DFA 150-450 and Sigma 100-300 F4.

I would go with a faster and longer prime:
a) Pentax DA 50mm f/1.8....hard to beat at under $100: https://www.bhphotovideo.com/c/product/864663-REG/Pentax_smc_DA_50mm_f_1_8.h...981&
b) Pentax DA Limited 70mm f/2.4....in your budget and better suited for portraits than your 40mm: https://www.bhphotovideo.com/c/product/1002138-REG/pentax_21430_hd_pentax_da...981&
c) Pentax 55mm DA* f/1.4. This is easily the best answer if you can stretch your budget $50. Top quality: https://www.bhphotovideo.com/c/product/594340-USA/Pentax_21790_Telephoto_55m...981&

[Cerebum]

Where to start. ... Limiteds ....the finest primes on the planet well, I think they are. I am excluding FA limited purely on price. DA limiteds range from £150-300. They all have a very special way of rendering. The pancakes (21, 40 & 70) are small enough for you to fit your camera and lens in a jacket pocket

15mm f4, lovely wide angle lens with legendary star bursts on the SMC version
21mm f3.2. Full of pixie dust, pancake, and flexible enough to use all day. Very sharp and quite inexpensive.
35mm f2.8 macro. Great all rounder. I used mine exclusively on a visit to Cadiz
40mm f2.8. Very similar to your XS, the only difference really is the look. Stunning lens
70mm f2.4. Quite fast and very sharp

Other superb lenses

FA 35mm f2 sharp, fast and cheapish

50mm f1.8 plastic fantastic. A brilliant performer for well under £100

The 15 & 70 can't really be called a walkabout but any of the others could sit on your camera all day. Primes enrich you photographically. The IQ is often, (but not always) better because their construction is generally simpler. As for using them, they make you think about composition because you have to zoom with your feet.

[jersey]

You have good lenses, I would stick to them and learn all about them and what or how you like to photograph. Then you will be able to decide what you like and what not and it will be easier to choose a new lens.

Primes can be pretty cool, zooms are more versatile. I am primarily zoom user, I love my 20-40 and 55-300. But I also have some primes I take out for specific roles when I know exactly what I am going to photograph and how.

[Cerebum]

If you want to explore a prime, why not do a single in challenge with your 40mm xs. Its a great way to learn all about a lens

[Michail_P]

You have good lenses, I would stick to them and learn all about them and what or how you like to photograph. Then you will be able to decide what you like and what not and it will be easier to choose a new lens.

Primes can be pretty cool, zooms are more versatile. I am primarily zoom user, I love my 20-40 and 55-300. But I also have some primes I take out for specific roles when I know exactly what I am going to photograph and how.

I’ll agree with you, that’s the best advice I would have taken for myself, probably. I think that every time I crave a lens... it really does make sense knowing that your lens can do better if you become a better photographer yourself.

[kypfer]

Well now that I have the telephotos I have been wanting...it is time for something with a shorter range. I thought I would have been done lens shopping after my second telephoto but for some reason, I can't help but to look for something else!

Should I be focused on a prime or a zoom? I have the 18-135 that came with my K-70 but I would like a higher quality lens for less than 600 or so. I am thinking I would be using it mostly for portrait's around the farm. Close up's of the animals, my kids while playing with them or having the pose with equipment etc. The 2 cameras I would be pairing it up with would be the K-70 and KP (whenever it gets repaired)

Currently I have the DA 40 F2.8 xs, DA18-135, 55-300PLM, DFA 150-450 and Sigma 100-300 F4. I will most likely be selling the Sigma since I just got the 150-450 2 days ago for a good price. The 40mm is the only prime I have experience with. Does it even compare to more expensive primes? I did some portraits with it for my wife and while she thought the pictures were great, I wasn't impressed (the content was outstanding though). The quality just seemed meh. I used the KP while taking them and I'm sure there was a level of user error involved but I've done better with the 18-135.

With that selection the Sigma would seem to be redundant!
For that range of subjects, kids and animals especially, I'd have thought a good zoom was an obvious choice … by the time you've decided which prime to use something will have moved and you'll have to change it anyway
I don't have the 18-135mm, but if I did, and judging from the results I've seen and the reports I've read, it'd be an obvious choice for a lot of my pictures.
I'm very pleased with my DA 40mm XS, but sometimes I get the impression I'm less critical than many
Good luck

[robgski]

The DA 40 XS is an exceptional lens, I have it with me in my bag or pocket.

The FA 77mm is a great high quality prime, I recommend it.

Shooting with primes makes a person really think about composition, zooms make me a lazy photographer.