[pentasonic49]

Pretty well all the macro lenses from 90mm focal length upwards which have an "A" position on the aperture ring, (for ease of use) will do, there is unlikely to be a bad one. Autofocus is not required, but as the lens would also have other uses such as portraiture it could come in handy. This is one type of lens which all the manufacturers have always produced quality products, so its mainly your budget which governs the choice. It is well worth checking out the lens database on this forum for inspiration.

[csa]

I haven't seen this one mentioned:

Sigma EX 105 F2.8

I have this one, and am very pleased with it! Photo was handheld

I guess "What do you call cheap" with regards to the Irix their lens is 150mm 1:1 WR and lists for over $500 ??

(Photo is my own copywrite Photodirector in error)

Perhaps I should have said, "less expensive"; compare the price of the Pentax 100mm.

[tryphon4]

Any macro lens, in K or PK or PKA mount, could be used on a K100D.

The big question is about budget: you can find used or brand new macro lenses between less than 100$ (Cosina 100mm F3.5) and more than 1000$.

Another interesting question is about magnification: most macro lenses go from 0:1 to 1:1.
Do you need higher magnification?

[35mmfilmfan]

Less expensive options include the use of a short extension tube on any lens with an aperture ring, or a reversing ring on a standard lens, again with aperture ring. Manual focus only of course with these options. And, of course, using an extension tube on a true macro lens will enable a larger image to be produced.

[tryphon4]

I still own a K100D super, it was my first DSLR.

I started macro using the standard 18-55mm lens and a magnifying glass. This very basic setup can give good results:



Several months later, I bought my first macro lens, a Cosina 100mm macro F3.5. It can reach 1:2 alone and 1:1 if you use the dedicated close-up.
Then I bought one 1.4x teleconverter and 2 extension ring kits, here is a setup enabling about 5:1:



Later, I bought a Tamron 90mm macro (model 52B), my first Tamron. Then I bought (and sold) many other macro lenses.


I currently own 6 macro lenses from 60mm to 180mm, they reach 1:1 to 5:1, I love each one.

I sometimes revert a wide angle lens (35mm e.g.) and maybe add one or two extension rings.
I also can add a close-up to a telelens (the Pentax DA* 300mm F4 performs well if you use it with a Nikon 5T or 6T close-up).


To summarize, the possible setups are endless. You just have to choose a lens according to your needs and you can add

-bellows or extension rings if it is a short focal,
-close-up if it is a long focal.

You also may try microscope lenses or enlarging lenses, it is weird but it works:





Practically, insects and bugs prefer longer lenses because the working distance is longer. So 100mm to 200mm is a good range.


There are lots of topics about maco lenses over there, you can read them in order to make your choice.

[35mmfilmfan]

No-one has yet mentioned lighting - I use a ring flash (not an led ring light), as the short flash duration freezes most movement. The downside of this is that modelling from shadows tends to vanish (although a piece of aghesive tape on the flash can help here), and the background becomes dark - isolating the subject, but creating an unnatural effect. Another flash on a bracket, fired by a wireless trigger and aimed to one side of the subject, can help here. The key is to experiment - and make notes of what you have done, so you can repeat any successful shots.

Many of the techniques described in Heather Angel's book 'The Book Of Close-Up Photography' can be adapted for digital use, of course.

[stemked]

I've collected probably too many macro lenses over the years. Here are a couple of my takes. If insects really are your thing then a 1:1 (or even higher mag) is where you want to be.
As others have noted, giving space to insects is very helpful. 100mm/90mm are the most affordable lenses to consider. What I love about the new 100mm f2.8 FA W is that it is water proof, very small. It's down sides are that it really isn't the best for manually focusing and it is rather fragile (at least in my hands). But it is a lovely 1:1 lens.

The new Lowa lines are fantastic as both the 100 and 60 are 2:1 (2X mag) for a great price.

I do have the Pentax 1:2 100mm f4 A, it's a lovely lens, but I used to have to use it with extension tubes for insects, IMHO. I also have the super sharp Tamron adaptall 90mm f2.5. Lovely lens too, but it is also a 1:2. If you are interested in either of these lenses let me know and I can see what I can offer you. Both are fantastic for flowers, again maybe a little less so for insects because of the 1:2 mag.

---------- Post added 09-26-2020 at 12:37 PM ----------

PS. You can make a "super marco" by reversing your lenses. There are dedicated adapters, very cheap, that will take a 49mm filter and others that take a 52mm thread. But you have to get super close to your subject.

[RobSpain]

I picked up an SMC 100mm M macro f/4 on eBay from a dealer in Japan that arrived in mint condition. And for just 70 Euros! Thoroughly recommend it for macro photography. SMC Pentax-M 100mm F4 Macro Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database

[EnglishBob]

Practically, insects and bugs prefer longer lenses because the working distance is longer. So 100mm to 200mm is a good range.


Exceptions: Bedbugs, mosquitoes, ticks, lice and their buddies when they settle down for a snack,

[Thagomizer]

Exceptions: Bedbugs, mosquitoes, ticks, lice and their buddies when they settle down for a snack,

In which case they're getting you!

[TwoUptons]

I know this is a fairly stale thread, but there are a couple of things I’ll throw in there...

The Cosina 100mm f3.5 is the same as the Pentax one. I have the Pentax autofocus one and really like it, though it makes a racket when it focuses. Make sure you get the matched 1:1 thing for the end... I think I paid just over $100 for the lens and the 1:1 adapter.

I’ve also had really good luck with a Raynox closeup filter on a Pentax SMC-A 200mm f4.0 telephoto lens.
That’s my go to for small insects, and the Raynox fits on most of the lenses I have.
I paid $90 for the lens and I think $69 for the Raynox.

The reversing ring is probably the cheapest way to get high magnifications.
Reversing a 50mm f2.0 on a 135mm f3.5 gives you better than 2:1 for very little money...

-Eric