[Arisenfromash]

Hi all,

I'm a great fan of older manual lenses, fantastic value vs. quality.
However, my 50mm rikenon lens is full frame giving some unwanted magnification on my crop sensor istd S.

Furthermore i commonly have things slighly out of focus due to the model, object moving.
The same is true for my 28 mm centax lens.

If anyone could recommend some budget options autofocus options i'd be happy.

Some of my recent efforts below

Attached Images

       

[Apet-Sure]

For a budget lens to give you the equivalent field-of-view of a 50mm lens on a full frame camera, you might consider this one:
SMC Pentax-DA 35mm F2.4 AL Reviews - DA Prime Lenses - Pentax Lens Reviews & Lens Database

It has a plastic mount, but seems to be good bang for the buck judging by the user ratings. I've never used one myself. You might find a used one for sale in the PF marketplace
The Pentax Marketplace | Buy & Sell Pentax Cameras and Lenses - PentaxForums.com

For an APS-C equivalent to a 28mm full frame lens, you'll need something in the 18mm range. The current DA series primes at 15mm and 21mm are pretty pricey unless you can find a great deal in the marketplace. Does it have to be a prime? There are various versions of the DA 18-55mm zoom. This one seems to have the best user ratings:
SMC Pentax-DA 18-55mm F3.5-5.6 AL II Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database

I owned the first version which came in a kit. It was very disappointing optically. I ended up getting a Sigma 17-70mm DC Macro which was a major upgrade. I think I paid around $250 used, so not exactly budget, but I've been quite happy with it.

Welcome to the forum.

[AfterPentax Mark II]

For your 50mm I would choose the Pentax DA 50mm f1.8 (then you get the same FOV as with the 50mm you own) and for your 28mm I too can recommend the Pentax DA 35mm f2.4. It is a bit less wide, but it is such a good lens (certainly for the money) and if you want real cheap just buy the mentioned 35mm to replace both your 28 and 50mm, because it sits somewhere in the middle. The "plastic" mounts are of a sturdy quatlity so do not be afraid of that and to be honest they usually mount in a smoother way than lenses with a metal mount .

[UncleVanya]

For a 50mm the DA 50/1.8 plastic fantastic is hard to beat. The F or FA 50/1.7 may also be a good option. As these may be too tight the DA35/2.4 plastic fantastic is cheap and nicer than it should be. I owned one, rejected it. Bought the FA 35/2 and it later broke (I had an accident and it broke the cameras fall) and recently I replaced it with another DA35/2.4 and I like it. The DA35 limited is another fine lens but a bit more. The DA21 comes up at reasonable used prices but will be more than these. Lastly a DA40 or DA40xs is a little wider than the 50mm a little narrower than the 35 and it renders people quite well in my opinion. That lens has really tumbled in price and might be in the range of cheap/bargain. I certainly like mine.

In zooms the HD DA 18-50 and 18-135 are shockingly good but optically slow. The old DA* 16-50 is often available cheap - and can be reliably converted to screw drive. It’s a bit weaker at 16mm than at 50mm but is a credible choice for this type of shooting.

Of all that I mentioned I’d want more info before making a final recommendation - but my initial thoughts:

#1) DA50/1.8 + DA35/2.4 this costs less than the 16-50, and the pair is more than the da40. It’s very capable and a good choice.
#2) DA40 I’d rank this first if the money is only enough for one lens and f2.8 is sufficient.
#3) DA* 16-50/2.8 SDM converted to screwdrive. I’d rank this first if the f stop is enough and the budget will bear it. Particularly if you use strobes or lights… you control enough that the dog and light aren’t an issue. This is similar to using a 24-70 on a full frame. A very popular option for studio work.

I’m not mentioning one of my favorites the DA* 55/1.4 - because some have drive motor failures and it is costly to repair and it is tighter framed than the 50 which you struggle with already. A person shopping for a bargain lens shouldn’t gamble on a potentially great lens that may fail on them.

---------- Post added 11-11-22 at 04:52 PM ----------

I forgot to suggest the FA 28/2.8 if wider is required and a prime is preferred.

eBay looks like these are cheaper than the F version.

[mikesbike]

However, my 50mm rikenon lens is full frame giving some unwanted magnification on my crop sensor istd S.

It isn't really magnification, but I understand what you mean. A 50mm lens on a body with an APS-C sensor will deliver a field of view (FOV) similar to a 75 or 77mm lens on a FF DSLR or a 35mm film SLR body. But this can be a good thing, if you are familiar with the cost of such lenses for FF use. A good 50mm lens on APS-C can be like a poor person's FA 77mm Ltd on a FF body. It is a good lens for Portraiture and much else.

As others have said, for the FF 50mm FOV on APS-C, you need a 35mm lens, and I too recommend either the Pentax DA 50mm f/1.8 or for low budget, a used Pentax FA SMC 35mm f/2 which is an exceptional performer for the cost.

28mm is a very interesting FL for APS-C. It has the same FOV as the unique but expensive Pentax FA 43mm f/1.9 Limited lens on a FF body, which is a very useful wide/normal. For this, I have found my now very old FA 28mm f/2.8 performs very well. I also have long had the FA 43mm Ltd bought for my film cameras years ago, and found it to be less interesting for APS-C, only recently to be once again employing it on my FF Pentax K-1 II. The 43mm Ltd is not all that good wide open anyway, so I think you would find the FA 28mm f/2.8 to be satisfying on APS-C as a wide/normal lens, as it is pretty good wide open. Should be able to locate one in fine shape used for a reasonable cost.

Be aware, these AF lenses are designed to optimize AF performance, and do not have the same "feel" for MF as do MF lenses.

[kypfer]

As previously recommended, the "budget" options, if looking for an a/f lens, are really the 35mm f/2.4 as a prime or one of the "kit" 18-55mm lenses, both perfectly good on a 6Mpixel *ist DS
Do be aware, the a/f on the earlier cameras, whilst very good "in their day", is a little slow by modern standards, so may not be the total solution you require.
A faster shutter speed may be a better solution for subject movement, which may not be practical with the smaller aperture of the 18-55mm lenses, so a wider aperture manual lens may preferable.

[steephill]

I can't find any reference to a 28mm centax lens. Can you check which lens it is?
AF might not be the solution to the problem of your blurred images. Is it truly subject movement or a slow shutter speed which is causing the problem? How are you lighting the shots?
The suggestions for the DA35 f2.4 as a crop sensor lens is a good one. It may be cheap but it is good.

[GUB]

However, my 50mm rikenon lens is full frame giving some unwanted magnification on my crop sensor istd S.

Just to clarify re your wording - the fact the lens is full frame capable doesn't change the nature of the magnification - an apsc lens of the same focal length would be the same. It is the cropping of your sensor that creates the magnification change compared to full frame.

[GUB]

Furthermore i commonly have things slighly out of focus due to the model, object moving.
The same is true for my 28 mm centax lens.

If anyone could recommend some budget options autofocus options i'd be happy.

Looks like you have been focusing on the lacework which is closer than the lovely model's face. Without being aware of this focus criticality an autofocus lens could well make the same mistake.
I am thinking you are using that 50mm wide open which aggravates the problem.

[pres589]

28mm on a Pentax APS-C body is the business. Unfortunately, if you want autofocus, you are limited to very few options; Pentax F 28, Pentax FA 28 (different optical formulas), and Sigma's EX DG f1.8. I have a copy of the Sigma and I really really like it except that it doesn't really autofocus that well in combination with my Pentax K-5 II. What might be a nice option that hasn't been mentioned yet is Sigma's 30mm f1.4's but they are not known to autofocus well on Pentax bodies. There are also some 24's that were made with autofocus available in K-mount.

[ChristianRock]

I loooove the Sigma 30mm f1.4. i think it's the perfect APS-C lens and I've been seeing used copies in the US200s range.

[Just1MoreDave]

I have the Pentax-F 28mm f2.8 and it is really good for me. For some reason the F version often goes for a higher price than the FA, even though the optical formula for the F is the same as the A or later M versions, where it wasn't as well-liked. The FA version does look different but I wouldn't call it worse. For people, maybe the Pentax-DA 21mm f3.2 works sometimes but I think is generally too wide or I am not good enough. The SMC version is cheaper.

[Terry C]

Full frame 50mm lens will not give any more "magnification" than a crop sensor 50mm . FoV will be the same. For a wider FoV, go for the 35mm f2.4 plastic fantastic.

[photogem]

There is for sure no unwanted magnification if you use a fullframe lens on an APS-C Pentax!

50mm: DA50/1,8 is cheap and excellent for the money, the F50/1,7 a bit better, more solid
28mm: maybe go for 30mm and a Sigma or FA31/1,8. DA35/2,4 is always good but might be not wide enough.
Sigma Miniwide 28mm is an A-lens but manual focus, quite cheap and good enough

[pres589]

I don't think the Miniwide was considered a great optic in its day. A good condition Pentax F or FA 28 f2.8 should outperform it optically while bringing autofocus. Seems like either would cost about $150 or so in today's market based on sales I see here.

The Sigma 24mm Superwide II AF, when it was new, was considered a pretty good performer and seems to be based on images shared here (save for sometimes quite busy out of focus backgrounds). With these options I don't know that I could recommend the 28mm Miniwide.