[Thagomizer]

Unless I'm much mistaken, when macro shooting at a given magnification, depth of field is going to be the same regardless of focal length. What changes with focal length is working distance, (the distance between the front element of the lens and your subject [not to be mistaken for focusing distance, which is measured from the sensor or film plane]), and angle of view. Longer focal length lenses give more working distance at a given magnification, with a narrower angle of view.

[Apet-Sure]

I bought a Pentax-F 100mm f2.8 Macro from a PF member in the marketplace. It is an excellent lens, as its descendants are. As others have said, it isn't WR. I find the focal length very useful for flowers and insects. But, at close focus distances and wide apertures, the DOF is razor thin. I often have to close down to f11 or more for usable DOF. The lens is basically so sharp that diffraction softening hasn't been an issue at f16 or maybe even f22. I've had to train myself not to shoot at the lens's minimum focus distance, but to back up a little to optimize DOF or use a wider aperture. I now have a 24MP KP, so this helps with resolution over the K-5IIs which I first used with this lens.

[mikesbike]

Since you say you are sometimes caught in a rainy situation, the Pentax DFA 100mm f/2.8 macro WR lens should be a fine choice for you. Image quality is of very high order!

[Wasp]

And then there is the ne plus ultra of Pentax macro lenses. Not really relevant, but I think it deserves to be mentioned.

SMC Pentax-FA* 200mm F4 Macro ED [IF] Reviews - FA Prime Lenses - Pentax Lens Reviews & Lens Database

Rare and expensive, but those who have them love them. It scored a perfect ten in the reviews. Weather protection? Better take an umbrella, preferably with an assistant to hold it.

Edit: the OP can also consider this one if the idea of a longer focal length is appealing.

Sigma 180mm F3.5 APO EX DG IF Macro Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Having said all that, just get the 100mm - the safe choice.

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Last edited by Wasp; 05-19-2020 at 01:39 AM.

[clackers]

+1 to the DFA 100mm f2.8 Macro. Only a 49mm filter size, so smaller than the other brands, WR, good metal build, probably not far off being a Limited.

For flowers and insects you may find yourself at f11 without stacking, so a flash and suitable modifier become attractive, too.

[stihlmania]

Advice please hive. I have a K3 and two lens - a SMC DA 18-55mm AL WA and a HD DA 55-300mm ED WR
What I am looking for is a prime lens that I can use in the field for flower and insect photos. Depth of field is important as the subjects often move and with the lens I have I get a lot of duff shots. Often there is only once chance to snap the subject before it vamooses. Preferably the lens would be one that is also weather proof as I am often caught out in the rain.
I tend to use the 18-55 but I have to get very close, often frightening the subject away and the depth of field is problematic especially in even mildly breezy conditions. I confess to not understanding the jargon used on the website, especially initials like CA. I have looked at various threads and reviews but seen no real answers, but was wondering what people would recommend. Would a 100mm macro do the job? I look forward to your expert opinions, thank you.

I have the same HD 55-300 and it is what I use ( most of the time ) for insects here. Set the zoom at 250+ and the f stop f11 or higher for depth of field as the insects will not let me get close with a macro under 200 mm. Duff shots are part of life here, it happens....(The swallowtail was shot with a SMC A 50 f1.7 with the AF 1.7 adaptor...)

[mikesbike]

I have the same HD 55-300 and it is what I use ( most of the time ) for insects here. Set the zoom at 250+ and the f stop f11 or higher for depth of field as the insects will not let me get close with a macro under 200 mm. Duff shots are part of life here, it happens....(The swallowtail was shot with a SMC A 50 f1.7 with the AF 1.7 adaptor...)

Hmmm.... I've never tried my HD 55-300mm WR for closeups before, but this impressive shot has me eager for that experience! I have been very pleased overall with this lens, and better still with my KP, and now it looks like yet more satisfaction to look forward to!

My DFA 100mm f/2.8 is still the epitome, however. But the long zoom lens would be great for shooting non-macro closeups from longer distances! And being not of internal-focus design, there is no "focus breathing" to effectively shorten FL at moderate distances, reducing the image size.

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Last edited by mikesbike; 05-19-2020 at 05:55 PM.

[normhead]

I own the Pentax 50 macro, the Sigma 70 macro, the Tamron 90 (Tess's lens) and the DFA 100 macro 2.8 WR.

I use the DFA 100 macro, sometime with the HD DA 1.4 TC.
Tess uses the Tamron 90 macro sometimes with the Tamron WC7 2x TC.
The 50 macro and SIgma 70 sit largely unused.

Either is WR, the Sigma is very big compared to the others, but might be the best overall among them. The Truman is nice, no complaints except Tess stole it from me. The 100 has everything. Lightweight, small compared to the others and a very small footprint indoor camera bag, WR really not that expensive.

K-1 and DFA 100 macro WR


K-3 and DFA 100 macro


K-3 and DA 55-300 PLM


For many insect images the magnification of the DA 18-135 and DA 55-300 PLM make a true macro unnecessary.

Pentax DA 18-135

[stihlmania]

Hmmm.... I've never tried my HD 55-300mm WR for closeups before, but this impressive shot has me eager for that experience! I have been very pleased overall with this lens, and better still with my KP, and now it looks like yet more satisfaction to look forward to!

My DFA 100mm f/2.8 is still the epitome, however. But the long zoom lens would be great for shooting non-macro closeups from longer distances! And being not of internal-focus design, there is no "focus breathing" to effectively shorten FL at moderate distances, reducing the image size.

It may take a few trial and error moments but the HD DA 55-300 can get great macro images, also being stealthy always helps with any lens to be able to get as close as possible before the object of your photo attempt decides to flee! I think the minimum focus distance is + or - 7 feet.

[bassek]

If AF is not a must, M-series lenses can be available at a low cost, mainly the M28, M50, M135 are good buys, and even the M100 macro is rather affordable.
The A-series are more expensive.

Seb

[aslyfox]

It may take a few trial and error moments but the HD DA 55-300 can get great macro images, . . .

I guess it depends on your definition of " macro "

Typically, these lenses can reproduce small objects at up to 0.5x life size on a camera’s imaging sensor. In most cases, dedicated macro prime lenses go further still, enabling full 1.0x or 1:1 magnification at their closest focusing distances.

That might not sound particularly impressive, but bear in mind that an APS-C format image sensor is only about the size of a standard postage stamp. You’re therefore filling the entire image frame with something very small and, once the captured image is displayed on a screen or printed on paper, the degree of enlargement is enormous – a macro lens can reveal almost microscopic levels of detail, and make tiny bugs look like giant alien invaders.

The key question is: what makes a ‘good’ macro lens? Let’s take a look at the specifications and features that are important to consider. . .

https://www.techradar.com/how-to/what-is-a-macro-lens-magnification-and-minimum-focus-explained

of course, you can refer to the lens reviews for the " official " magnification of a lens

Max. Magnification 0.3x

HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database

Max. Magnification 0.28x

https://www.pentaxforums.com/lensreviews/hd-pentax-da-55-300mm-f4-5.8-ed-wr.html

my first " macro " lens was an old Tamron 70 - 300 telephoto capable of 1:2

[Froth Ninja]

I have the same HD 55-300 and it is what I use ( most of the time ) for insects here. Set the zoom at 250+ and the f stop f11 or higher for depth of field as the insects will not let me get close with a macro under 200 mm. Duff shots are part of life here, it happens....(The swallowtail was shot with a SMC A 50 f1.7 with the AF 1.7 adaptor...)

Will have to give that a try on the next sunny day. Always baulked at shooting without a tripod at that magnification for fear of camera shake

[basrietkerk]

Interesting readings. I have the sigma 70mm macro. It is a gem. Together with my K3ii, it gives clear, sharp, colourful pictures and a nice bokeh. Especially for flowers and insects. And yes, you have to kneel down and come close to your subject for a good macro.
Once and a while I use my pentax 55-300mm for the more shy creatures. This thread gives me a boost to do more with this tele when it comes to the smaller objects.