[ChristianRock]

I know 28mm lenses are not usually recommended for closeups, especially the slower aperture versions. They're first and foremost landscape lenses... but they might be used as walkaround lenses as well, and why not? So how would my two 28mm lenses compare in my most basic of tasks... taking pictures of some flowers?

Here's the SMC-M 28mm f/3.5... not a lens made for bokeh, that is for sure. But wide open, when the aperture blades are out of the way, it should do a little bit better, right? Well, maybe not...


Then the Rikenon 28mm f/2.8... I know it's 2/3 of a step faster but I wasn't ready for the how much difference in bokeh there was. And the rendering also seems more "lush" and nice looking to me.


I have tended to use 24mm lenses for these kind of shots, as their bokeh is usually better, but the Rikenon probably beats the ones I have tried (SMC K 24 2.8, SMC A 24 2.8, Vivitar (Cosina) 24 2.8 and Tokina 24 2.8). And the funny thing is, the Rikenon at longer distances is as sharp as the SMC-M, if not sharper. I think it needs to get back in my bag more often...

[pres589]

That Rikenon seems like a nice 28! I should do something like this as well with my collection of 28's.

[IgorZ]

I would not have thought there would be such a big difference! Thanks for posting!

[BigMackCam]

I'll admit, I'm surprised by the difference, too.

It's *so* different that I wonder if either the Rikenon is a bit faster than f/2.8, or the M28/3.5 is a bit slower than f/3.5... When you look through the lens, is the diaphragm opening up fully?

Anyway, the Rikenon takes the prize for bokeh, here. Nice result. That said, the detail from the M28/3.5 is lovely.

[D1N0]

Colours and contrast on the M-28 are a lot better though.

[normhead]

Never be surprised by a half stop difference in ultra wide angle lenses. With my 100 macro, half stop is barely noticeable. With a wide angle, every half stop counts.

[ChristianRock]

I'll admit, I'm surprised by the difference, too.

It's *so* different that I wonder if either the Rikenon is a bit faster than f/2.8, or the M28/3.5 is a bit slower than f/3.5... When you look through the lens, is the diaphragm opening up fully?

Anyway, the Rikenon takes the prize for bokeh, here. Nice result. That said, the detail from the M28/3.5 is lovely.

Yes, both are working properly.

I forgot to mention, both pictures were taken with the K10D and processed equally in Darktable with nothing but my standard initialization profile, and the exposure of the Rikenon picture was brought up a little bit to match the SMC-M picture.

[D1N0]

Never be surprised by a half stop difference in ultra wide angle lenses. With my 100 macro, half stop is barely noticeable. With a wide angle, every half stop counts.

I did a little test with three lenses.
The Vivitar MC Wide-Angle 28mm F2
Pentax-m 28mm f3.5
Pentax-a 28mm f2.8

Vivitar at F2


Vivitar at f2.8


Vivitar at F3.5


Pentax-m 28mm F3.5 wide open


Pentax-A 28mm at f2.8


Pentax-A 28mm at f3.5


Though there is a difference it is not nearly as dramatic. I used a tripod so the focussing distance remains the same. Makes me wonder whether the dramatic difference in christians pic is just due to special circumstances maybe in combination in the difference in contrast between the two lenses.

[normhead]

Do the OPS lenses have the same focus breaking properties?

[D1N0]

I must say that when you skip through the pics enlarged on flickr you see more of a difference, especially with the Vivitar. This was shot on the k-1 so any differences are less zoomed in upon than with an aps-c sensor.

[pres589]

norm, what does "focus breaking properties" mean?

[normhead]

norm, what does "focus breaking properties" mean?

It's apparently a spell checked way of saying "focus breathing".
An internal focus lens is different than a lens that focuses by moving the front element forward. FL is determined by FoV at infinity. Lenses at 10 feet can be very different from their stated focal length in terms of field of view.

Looking at the second posted images, when I shoot 70mm-100macros I often shoot ƒ2.8, ƒ4 or ƒ5.6, ƒ11or ƒ16 so two stop increments. Based on the above photos, there's enough difference I'd be shooting half stop increments. That's all I'm saying here.

There's enough difference one could be distinguished from and judged better or worse than the other. When that's the case, I want to pick and choose. I'm not going to let my prejudices decide which I'll like most. My prejudices are too often wrong. You can't judge bokeh without a picture. Prejudging is a mistake. Way too often, I've selected an ƒ11 images as the best, when if I'd decided it was an ƒ4 kind of shot and just taken an ƒ4 image I wouldn't have the shot I wanted. I'm guessing from the look of the test images you probably want to limit your shots where smooth bokeh is required to less than ƒ3.5, but you might still want to bracket to see how much less.

[Just1MoreDave]

I thought I'd try two of my 28mm lenses that are very different. The first is labeled "Auto Sears Multi-coated 1:2.8 f=28mm" with a 52mm filter. It focuses to 0.2m and has a basic PK mount. The second is a "Sigma High-Speed Wide 28mm 1:1.8 Aspherical Manual Focus" - typical 0.3m minimum focus, 58mm filter, KA mount. The Sigma has an AF version and is on the timeline somewhere between the Miniwide and the 77mm AF lens that's also f1.8.

Both photos are at 1/30, f2.8, ISO80, 2 sec. delay on a tripod. I think they are focused on the same spot but the Sears is not that easy to tell. The Sigma has an advantage by being stopped down, but it is a really sharp lens anyway, while the Sears has a lot of coma. My guess was that the Sears would have better bokeh, but I don't like that either. Anyone want a Sears 28?

[normhead]

I love it when these threads turn into "image evaluation of different parameters" threads instead of "here's my opinion" threads. Thanks to everyone taking and posting images. That's info you can take to the bank.

Especially since everyone of us has a different idea about when the image is "smooth" enough, and how much loss of detail due to narrow depth of field is acceptable.

[leekil]

I can't even tell that the Sears is focused...