| View previous topic :: View next topic |
| Author |
Message |
dnas
Joined: 14 Nov 2008
Posts: 488
Location: Japan
|
 Posted: Sat Aug 29, 2009 1:01 pm Post subject: |
 |
|
dnas wrote:
Do you mean smaller apertures or small F stop numbers? |
|
| Back to top |
|
 |
Jieffe
Joined: 04 Nov 2007
Posts: 754
Location: Belgium
|
| Posted: Sat Aug 29, 2009 1:09 pm Post subject: |
|
|
Jieffe wrote:
| dnas wrote: |
| Do you mean smaller apertures or small F stop numbers? |
Problem beginning at f8 and getting worse as you close the aperture until f22 ... which is quite annoying for a macro lens 
Inspired by the Olympus forums, I tried fitting a black cardboard baffle to reduce the rear lens diameter but it had no effect on the spot (need to experiment with different hole sizes though). |
|
| Back to top |
|
|
Mike Deep
Joined: 25 Oct 2008
Posts: 323
Location: Upstate New York
|
| Posted: Sat Aug 29, 2009 6:27 pm Post subject: |
|
|
Mike Deep wrote:
Jieffe, I've read on FM that the problem has to do with the rear element being so flat. Probably not much that can be done about this.
_________________
Rocket Launch Photography
Olympus: 24/2.8 MC, 28/3.5, 28/2.8 MC, 35/2.8, 50/3.5, 50/1.8 MC, 50/1.4 MC, 35-70/3.6, 75-150/4
Nikon: C 24/2.8, AI-S 28/2.8, K 35/2, K 35/2.8, F 55/3.5, C 55/1.2, AI 85/2, 105/2.5 (5/3), 105/2.5 (5/4), F 135/2.8, F 200/4, No. 5T
Pentax: 28/3.5, 35/3.5, 50/1.4 (8/6), 50/1.4 (7/6), M 50/1.4, SMC 55/1.8, 105/2.8, SMC 135/3.5, 150/4
Tamron: SP 17/3.5 151B, 28/2.5, 135/2.8 T-135, SP 300/2.8 60B, SP 35-80/2.8-3.8 01A, 80-210/3.8-4 103A, SP 1.4x TC 140F, SP 2x TC 01F
Vivitar: 24/2 (Kino), 28/2 (Kino), 50/1.4 (Cosina), S1 90/2.5 (Tokina), S1 28-80/2.8-3.5 (Kino), 70-150/3.8 (Kino), S1 70-210/3.5 (Kino), 2x Macro TC
Etc: Yashica 3.5cm/2.8, Fujinon 50/1.4, Yashica ML 50/1.4, Tomioka Yashinon 55/1.2, Mamiya/Sekor 55/1.7, Sigma 90/2.8
That's a lot of 50s. |
|
| Back to top |
|
|
dnas
Joined: 14 Nov 2008
Posts: 488
Location: Japan
|
| Posted: Mon Aug 31, 2009 12:31 am Post subject: |
|
|
dnas wrote:
| Jieffe wrote: |
| rawhead wrote: |
| That is, after the Adaptall-PK adapter finally arrived, I got to play with it one day on my K20D.... |
On your K20 and/or K7, do you have a blue-ish circle in the middle of the picture when shooting at small apertures ?
My copy does it sometimes on both my Samsung GX1S and Pentax K200D. I read it is caused by light reflection on the sensor because of the large rear lens. |
| Jieffe wrote: |
| dnas wrote: |
| Do you mean smaller apertures or small F stop numbers? |
Problem beginning at f8 and getting worse as you close the aperture until f22 ... which is quite annoying for a macro lens
Inspired by the Olympus forums, I tried fitting a black cardboard baffle to reduce the rear lens diameter but it had no effect on the spot (need to experiment with different hole sizes though). |
| Mike Deep wrote: |
| Jieffe, I've read on FM that the problem has to do with the rear element being so flat. Probably not much that can be done about this. |
I've just tried that, and yes, it does do that!!
I don't think any amount of baffling will help. Yes, it looks like it's reflection off sensor & the flat rear element.
I tried this on a Panasonic G1, and when you change the aperture, you can see the circle getting bigger and smaller. You can also see the shape of the aperture blades.
Because I'm using a G1 (micro 4/3), I could insert a clear multicoated filter in the micro 4/3 adapter, to see if the multicoated filter can reduce these reflections. |
|
| Back to top |
|
|
Mist
Joined: 28 Jul 2009
Posts: 134
Location: Toronto, Canada
|
| Posted: Mon Aug 31, 2009 2:34 am Post subject: |
|
|
Mist wrote:
Sharp lens with wonderful bokeh. |
|
| Back to top |
|
|
AhamB
Joined: 22 Jun 2008
Posts: 733
Location: Germany
|
| Posted: Mon Aug 31, 2009 8:55 pm Post subject: Re: Tamron SP 90mm f2.5 macro |
|
|
AhamB wrote:
| Jieffe wrote: |
| rawhead wrote: |
| That is, after the Adaptall-PK adapter finally arrived, I got to play with it one day on my K20D.... |
On your K20 and/or K7, do you have a blue-ish circle in the middle of the picture when shooting at small apertures ?
My copy does it sometimes on both my Samsung GX1S and Pentax K200D. I read it is caused by light reflection on the sensor because of the large rear lens. |
Do you have the old metal version with 52mm filter or the newer 55mm plastic version? I've read that the newer (55B) version doesn't suffer from this problem because it has improved coatings. |
|
| Back to top |
|
|
Jieffe
Joined: 04 Nov 2007
Posts: 754
Location: Belgium
|
| Posted: Mon Aug 31, 2009 9:18 pm Post subject: Re: Tamron SP 90mm f2.5 macro |
|
|
Jieffe wrote:
| AhamB wrote: |
| Do you have the old metal version with 52mm filter or the newer 55mm plastic version? I've read that the newer (55B) version doesn't suffer from this problem because it has improved coatings. |
I unfortunately have the old model, 52B, with 49mm filter thread. |
|
| Back to top |
|
|
Nesster
Joined: 24 Apr 2008
Posts: 5883
Location: NJ, USA
Expire: 2014-02-20
|
| Posted: Mon Aug 31, 2009 9:21 pm Post subject: |
|
|
Nesster wrote:
I got the blue with the 52BB, though there was a lot of light and white paper background flying around. I was sort of surprised, I even used the deep lens hood.
_________________
-Jussi
Camera photos
Print Photographica
|
|
| Back to top |
|
|
Maple Wang
Joined: 07 Jul 2009
Posts: 37
Location: Taiwan
|
| Posted: Mon Sep 07, 2009 11:45 am Post subject: |
|
|
Maple Wang wrote:
here is a picture taken by 52B yesterday, I think it's kind of sharp 
 |
|
| Back to top |
|
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Search
Memberlist
Register
Profile
Log in to check your private messages
Log in
