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Pentax 105/2.8 Super Takumar as a tube lens - big surprise!
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mjkzz



Joined: 01 Jul 2015
Posts: 841
Location: California/Shenzhen

PostPosted: Mon Apr 16, 2018 2:54 pm    Post subject: Reply with quote

rjlittlefield wrote:
mjkzz wrote:
because I tried the Canon 100mm f/2.8 macro and I got almost dark vignetting at corners

Exactly which lens was that, and on what sensor size?

I ask because I routinely use Canon EF 100mm f/2.8L IS USM as tube lens on APS-C, and that combo works very well.

--Rik


Oh, it is that old Canon EF-100mm f/2.8 macro + generic PLAN infinite objectives I have, not mitties, with my Canon 550D or Canon 600D, I will shoot a stack when I get some batteries.
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mjkzz



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PostPosted: Mon Apr 16, 2018 3:37 pm    Post subject: Reply with quote

per request in private message, here is what I use to adapt the M42 lens to EOS. It is the so called "precision" one, machined out of brass, not sure why they are all chrome instead of black, this type is not good if you use it to mount in front of extension tube

Anyways, with this adapter, you can focus to infinity and it does when I set the lens to infinity mark (it actually is a hard stop)

Adapter itself



focused to infinity (about 2 miles out), taken with Canon 6D, a full frame camera (so it works with full frame, too)

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Last edited by mjkzz on Mon Apr 16, 2018 7:26 pm; edited 1 time in total
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mjkzz



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PostPosted: Mon Apr 16, 2018 4:14 pm    Post subject: Reply with quote

rjlittlefield wrote:
mjkzz wrote:
because I tried the Canon 100mm f/2.8 macro and I got almost dark vignetting at corners

Exactly which lens was that, and on what sensor size?

I ask because I routinely use Canon EF 100mm f/2.8L IS USM as tube lens on APS-C, and that combo works very well.

--Rik


Ok, here we go. In stead of shooting a stack, I think shooting a flat surface should be sufficient, so the subject is a piece of white plastic foam. I think the extra 5mm focal length might be the reason, rather than the lens itself, nonetheless, the Pentax 105mm seems to have less vignetting.

With my generic PLAN 4X objective on 105 SMC vs Canon EF-100



With my generic PLAN 10x objective on 105 SMC vs Canon EF-100


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rjlittlefield
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PostPosted: Mon Apr 16, 2018 5:13 pm    Post subject: Reply with quote

mjkzz wrote:
Ok, here we go. In stead of shooting a stack, I think shooting a flat surface should be sufficient, so the subject is a piece of white plastic foam. I think the extra 5mm focal length might be the reason, rather than the lens itself, nonetheless, the Pentax 105mm seems to have less vignetting.

Yes, single image is fine.

The most important difference between tube lenses is the location of the entrance pupil. Lenses that play well with objectives have an entrance pupil that is relatively far forward; lenses that don't, have it farther back.

The vignetting with your 4X objective may be due to the objective's limited field of view at its front end. My Nikon CFI BE 4X on EF 100mm f/2.8L IS USM has either significant corner darkening or none at all, depending on whether I remove the hood from the front end. (http://www.photomacrography.net/forum/viewtopic.php?t=18182)

--Rik
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Beatsy



Joined: 05 Jul 2013
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PostPosted: Mon Apr 16, 2018 5:23 pm    Post subject: Reply with quote

Thanks for the pics. I think you're right - it is the extra 5mm of focal length that hides the vignetting, but the source of that vignetting is the objective itself. The 600D sensor is 22.3 x 14.9mm while the Sony A7rii crop mode uses a 24mm wide area, so it would probably show even more vignetting with that objective. It shows none with the Mitties on the same FL tube.

While I'm here - I just fiinished a deep test stack of my first critter with a 10x Mitty on the 105mm Takumar (5.25x on crop-mode sensor - covering 4.9mm FoV). Whole frame and a 100% crop below. I did no post processing at all (other than resizing the first and cropping the second for upload). SooC RAWs exported to TIFFs, stacked with PMax and uploaded as-is. No sharpening, levels or adjustments of any kind. No retouching either - so lots of transparent hairs and hazy bits. I even left the "streakies" at the bottom of the full frame (the foreground leg sagged a little during capture of the stack). Next one will be better...

I think you'll agree though, the base image quality is pretty darn good!


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mjkzz



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PostPosted: Mon Apr 16, 2018 6:53 pm    Post subject: Reply with quote

Yes, the objective almost touched the front lens for both SMC-100 and EF-100, I actually was afraid that they scratch those lenses.

OK, let me emphasize the qualifier that I am using MY OBJECTIVES, not mitties :-), so test result are for those objectives and it shows the difference, the extra 5mm COULD be the cause for the difference, nonetheless, it does help.

The reason I gave the SMC away the first place is because I have a 70-300mm zoom and played with it, with that zoom lens, I have to set zoom at 135 to reove vignetting, so I thought that is the limit for tube lens, and as matter of fact, I actually got a Zhongyi 135 as tube lens. But now, I know the lens is a factor, too. So, yeah, lens maters.
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Lou Jost



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PostPosted: Mon Apr 16, 2018 6:57 pm    Post subject: Reply with quote

It is very impressive that you were able to get down to 135mm with your 70-300 zoom without vignetting. The zooms I have tried cannot be pushed down very much without vignetting.
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mjkzz



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PostPosted: Mon Apr 16, 2018 7:04 pm    Post subject: Reply with quote

it is an old Nkikor 70-300, paid 99USD back in 2004
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Lou Jost



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PostPosted: Mon Apr 16, 2018 7:14 pm    Post subject: Reply with quote

May I ask which one? Do you like the results when used with an objective?
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mjkzz



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PostPosted: Mon Apr 16, 2018 7:23 pm    Post subject: Reply with quote

rjlittlefield wrote:
mjkzz wrote:
Ok, here we go. In stead of shooting a stack, I think shooting a flat surface should be sufficient, so the subject is a piece of white plastic foam. I think the extra 5mm focal length might be the reason, rather than the lens itself, nonetheless, the Pentax 105mm seems to have less vignetting.

Yes, single image is fine.

The most important difference between tube lenses is the location of the entrance pupil. Lenses that play well with objectives have an entrance pupil that is relatively far forward; lenses that don't, have it farther back.

The vignetting with your 4X objective may be due to the objective's limited field of view at its front end. My Nikon CFI BE 4X on EF 100mm f/2.8L IS USM has either significant corner darkening or none at all, depending on whether I remove the hood from the front end. (http://www.photomacrography.net/forum/viewtopic.php?t=18182)

--Rik


took out the hood for my 4x, I think it improved slightly, but not as much as to be decisive...but good to know another trick




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Last edited by mjkzz on Mon Apr 16, 2018 7:25 pm; edited 1 time in total
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mjkzz



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PostPosted: Mon Apr 16, 2018 7:24 pm    Post subject: Reply with quote

Quote:
I think you'll agree though, the base image quality is pretty darn good!


darn good? I think they are excellent.
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mjkzz



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PostPosted: Tue Apr 17, 2018 4:17 am    Post subject: Reply with quote

Just want to show comparison between a Mitty 5X and a Mitty 2.5X QV. Since the QV 2.5X needs 100mm tube lens, so it should not have any vignetting so it is a good reference to compare to. [edit] If you squint, you can see slight vignetting for the Mitty 5x compared to the QV 2.5X[/edit]


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JH



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PostPosted: Tue Apr 17, 2018 9:29 am    Post subject: Reply with quote

My experience is that sometimes a short empty tube between the lens and the camera can reduce vignetting.
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Jörgen Hellberg
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