Originally posted by photolady I have the following lenses; M 28-80mm; AF 18-55mm, two long zooms; AF 70-300mm and M 100-500mm, plus one M 50mm. What would be a good go between from the 28-80mm to the 70-300mm? I was thinking a long prime, but I need your input to help me decide. Bear in mind, I'm on a fixed income so price should be not more than $150.
Thanks in Advance.
I'll start in the other end and give some advice on good lenses on a budget.
You are not that specific on what actuall lenses you have. There are for example a mountain of different 50's, and zoom lenses in these ranges. And quality can differ a lot.
The SMC Pentax-M 50mm f1.7 and the SMC Pentax 55mm f1.8 are probably the most quality for the least money when it comes to 50mm options. Much cheaper than the f1.4 versions. Pictures from the 50/1.7 and 55/1.8 also comes out rather different, the 1.7 generally sharper, and the 1.8 warmer in colors. You should be able to get either of them for about 50USD or less.
The standard set of primes before zoom lenses took over was a 28mm, a 50mm and a 135mm, so they were sold in great numbers and hence there are inexpensive options for them all. Today on a APS-C DSLR the crop factor turns the 28mm into a normal lens, the 50mm into a portrait lens, and the 135mm into a 200mm proxy, which was also a standard prime focal length back then, and usefull for example for indoor sports, outdoor portraits, domestic or zoo animals etc etc.
For examples of 135mm lenses (and shots with them), see the 135mm lens club. On your budget, the best K mount Pentax 135mm would be the SMC Pentax-M 135mm f3.5, followed by the SMC Pentax 135mm f3.5 (these are very different optics). The SMC Pentax 135mm f2.5 is better than both these, but is typically out of reach of your budget. Though with a bit of patience you might find it (I got mine for about 150 USD a couple of years ago, but I was lucky...and patient). There are numerous non-Pentax 135mm. Look at the 135mm club to get an idea of what is good or bad. The Sears "macro" version you have is a lemon, unless you want soft images as a special effect. Most 135mm lenses are way sharper than that.
Are you comfortable with using screw mount lenses with an adapter? That would add many bargain options. You may also run into the Takumar bayonet 135mm f2.5. Allthough it has a similar optical solution as severall other Pentax 135mm lenses, it has a simpler coating and therefore less contrast and is prone to flare, but with a good lens hood you can get good results anyway. The Takumar bayonet should go for less than 50USD (I payed about 20USD for mine), but some sellers try to give the impression that is is a SMC Pentax 135mm f2.5 they are selling and asks for 100-150USD. Just ignore them.
The SMC Pentax 28mm f3.5 is one of the sharpest lenses Pentax made, and should be just within reach for your budget. A fantastic landscape lens. The SMC Pentax-M 28mm f2.8 and f3.5 (completely different optics than the non-M version) are not as good, but also much cheaper, and for the price good options. Otherwise there are an endless number of different 28mm lenses in K mount or screw mount, both lemons and gems.
The SMC Pentax-A 35-105mm f4 that someone mentions is indeed a very good zoom, better than most, works well for portraits, and has constant max apperture. Should go for about 150USD.
But the best hidden secret among Pentax zoom lenses is the SMC Pentax-FA 28-70mm f4 (constant f4). It was sold as a slightly more expensive alternative to the cheap kit zooms on bodies like the Pentax MZ5 and similar. It turned out however that it was one of Pentax best designs ever in this range. People says it performs comparable to the way more expensive SMC Pentax-FA* 28-70/2.8. It is built very plasticaly, but is an optical gem, a truly great lens, but it yet go for very little, 100USD perhaps.
Another cheaply available prime option is the 200mm lenses. Pentax best bargain is probably the SMC Pentax-M 200mm f4, while the non-M version is a simpler optical solution that is not entirely up to the M version. Also here there are numerous non-Pentax K mount alternatives as the 200mm was probably the fourth most common focal length (after the 28+50+135).
If you go longer than 200mm you most likely end up outside your budget. A decent 400mm that is just inside your budget is the Tokina 400mm f5.6, but it has less contrast than the Pentax 400mm f5.6.