Olympus UK E-System User Group
Olympus UK E-System User Group

Join our unique resource for Olympus Four Thirds E-System DSLR and Pen and OM-D Micro Four Thirds photographers. Show your images via our free e-group photo gallery. Please read the e-group.uk.net forum terms and conditions before posting for the first time. Above all, welcome!


Go Back   Olympus UK E-System User Group > Cameras, lenses and system accessories > Lens focus > Telephoto

Telephoto Lenses with focal lengths longer than 60mm.

Reply
 
Thread Tools Display Modes
  #1  
Old 11th June 2011
peak4's Avatar
peak4 peak4 is offline
Full member
 
Join Date: Nov 2007
Location: Buxton, Derbyshire.
Posts: 1,727
Thanks: 131
Thanked 223 Times in 188 Posts
Likes: 220
Liked 195 Times in 130 Posts
Unhappy Another 50-200mm oddball

Well I thought I'd nip out and try my newly home made lens focus tester in view of the two recent posts regarding 50-200mm problems.
Since I knew mine was working fine with the EC-20, it seemed a good opportunity to have a play.
I'd already posted a few shots from Sri Lanka on another thread to prove it was a reasonably capable combination.

I went out to a local nature reserve the other evening to have a look at some orchids and tried a few insect photos whilst I was there with the 50-200mm & Ring Flash.
I completely failed to get any in focus at all and assumed it was down to me being an idiot.

First, The Lens Focus Tester (based on the commercial LensAlign one)
The methodology is fairly simple.
Using Bubble levels on both the camera tripod and in the tester, set everything up level.
Sight through the viewfinder and point the camera in the right direction. Replace lens cap.
Set the height and angle of the test target using the red dot laser to the centre of the lens cap.
Finely set the camera's centre focus point to the centre of the target.


Test 1 just the lens without any converters


Conclusion; its a mile out, front-focusing severely.
I repeated the test several times, with and without both converters, and got front focus each time.

70-300mm, 40-150mm and 14-150mm PanaLeica were all OK.
Bigma Front Focus a little bit.
90-250mm also Front Focuses, which is really annoying to say the least.

The E-3 is only just back from a checkup in Portugal, where the shutter was replaced under warranty; even though it was over 2 years old, so that should be fine.

I now need to re do the tests again with the same lens and different bodies and then return it to Oly when I've got to the bottom of what's going on. It's not that long since it was repaired when it started to part company with itself in the middle.
__________________
Best Regards
Bill

The nearest I have to a home page.
http://www.flickr.com/photos/peak4/
They're Watching You!
Reply With Quote
  #2  
Old 11th June 2011
birdboy birdboy is offline
Full member
 
Join Date: Jun 2011
Location: Essex
Posts: 1,387
Thanks: 349
Thanked 241 Times in 203 Posts
Likes: 182
Liked 341 Times in 163 Posts
Re: Another 50-200mm oddball

Bill I feel partly responsible for your problem sorry mate. So what's changed since Sri Lanka? Is anything in focus? Do you remember knocking the combination? I've studied and studied my pictures to try and pin point the time when things deterioted and it points towards the camera falling over on the collapsed tripod.

It seems Oly support are going to be busy.

There is nothing more frustrating (other than black light) in having expensive equipment and it not performing. Good luck in finding and fixing your focus.

John
__________________
John

OM-D E-M1, 12-40 f2.8 Pro, Tamron 14-150mm f5.8, E5, E3, Zuiko 50-200mm SWD, Zuiko 12-60mm SWD, Zuiko ED 70-300mm f5.6, 50mmf2, Zuiko ED 9-18mm f5.6, Sigma 50-500mm f6.3, EC14, EC20, RM-1, VA-1
Reply With Quote
  #3  
Old 12th June 2011
peak4's Avatar
peak4 peak4 is offline
Full member
 
Join Date: Nov 2007
Location: Buxton, Derbyshire.
Posts: 1,727
Thanks: 131
Thanked 223 Times in 188 Posts
Likes: 220
Liked 195 Times in 130 Posts
Re: Another 50-200mm oddball

The good new is that the 90-250mm isn't too bad on a variety of bodies, oddly worst with most Front Focus on the recently serviced E-3 and best on a Panasonic L10.

The 50-200mm however looks like it is after a holiday in Portugal again.
I had to make a longer ruler for the gizmo to work out where the point of sharpest focus was.
The Front Focus amounts to about 10cm in 4m


On the E-3


On the E-420


The E-1 was similar, but actually more accurate.

I guess I'll live with the 90-250mm and tune it in on my E-620 & E-5.
It seems that different bodies pick different focus distances repeatably with different lenses, and different Teleconverters have varying but repeatable effects on different lens/body combinations.
I'm beginning to understand why Olympus have introduced the focus fine tuning, but wonder of 20 combinations is sufficient.

The 2x teleconverter front focus effect was equally pronounced on the 300mm F2.8
Olympus in Japan commented that the converters caused an effect on the focus point. It was fine on its own and reasonable with an EC-14, but well out with the EC-20.
Unfortunately they could only set the lens up for one of the three scenarios.
I'll let you know how it performs when it returns from Japan.

The really bizarre thing is that it Back Focussed hugely with a 112mm front UV filter fitted. Olympus again acknowledged it, but were not able to adjust the lens accordingly.

Can anyone offer an explanation as to why a front filter should effect the focus point?
(I tried both a Tokina and a B+W filter; they both had the same effect. The rear filter was fitted for all tests)
With other lenses, you can attach filters or even close up lenses without effecting the focus point too severely.

Having just typed this last paragraph, I probably should repeat the 50-200mm tests without the front filter fitted to that as well.
In the case however, it used to focus fine, as was evident from the Bee Eater photo in the other thread.
__________________
Best Regards
Bill

The nearest I have to a home page.
http://www.flickr.com/photos/peak4/
They're Watching You!
Reply With Quote
  #4  
Old 13th June 2011
Daveart Daveart is offline
Full member
 
Join Date: Apr 2009
Location: Cartaxo Portugal, formally from Ross on wye UK
Posts: 654
Thanks: 33
Thanked 85 Times in 68 Posts
Likes: 13
Liked 39 Times in 32 Posts
Re: Another 50-200mm oddball

Hi Bill one explanation could be, if you did physics at school is light diffraction as in the image I have uploaded, no matter how good the glass is made their are imperfection no matter how much you polish the glass surface there will be fine grooves on each of the surfaces which will deflect light to the angle depended on how coarse or fine these grooves are as to how much the light moves from its original path, then there is the imperfections within the glass ie molecules within the structure which also moves light from its path.
Which would increase or decrease the distance, and as your lenses is constructed to counteract this and because your lens magnifies the object so it magnifies the error of the glass in the filter.

Dave
Attached Images
File Type: jpg Diffraction of light.jpg (85.3 KB, 11 views)
Reply With Quote
  #5  
Old 13th June 2011
peak4's Avatar
peak4 peak4 is offline
Full member
 
Join Date: Nov 2007
Location: Buxton, Derbyshire.
Posts: 1,727
Thanks: 131
Thanked 223 Times in 188 Posts
Likes: 220
Liked 195 Times in 130 Posts
Re: Another 50-200mm oddball

Cheers Dave, Seems odd that it only effects the 300mm though.

And it gets odder

I was just about the parcel up the 50-200mm, but thought I'd take a couple of "normal" photos to include with it, rather than just test shots.

Try as I might, I couldn't get it to front focus in the garden tonight; on rulers, fences, tables, hedges etc.

Previously either in sunlight, or artificial, on several bodies, it focused short.

A couple from this evening, OK they're not perfect by any means, but it wasn't very bright sunlight; yesterday, the whole flower was OOF.

E-3 Bee


E-5 Bee


So being satisfied all seems to have cured itself, on a temporary basis at least, I tried the AP test box just out of curiosity.

Somewhere between 4 1/2 and 5 front focus I think.
Back out with the bubble wrap
__________________
Best Regards
Bill

The nearest I have to a home page.
http://www.flickr.com/photos/peak4/
They're Watching You!
Reply With Quote
  #6  
Old 13th June 2011
Daveart Daveart is offline
Full member
 
Join Date: Apr 2009
Location: Cartaxo Portugal, formally from Ross on wye UK
Posts: 654
Thanks: 33
Thanked 85 Times in 68 Posts
Likes: 13
Liked 39 Times in 32 Posts
Re: Another 50-200mm oddball

Hi I can see what you mean in the images you show, the greater the magnification a lens has like telephoto primes lenses and telephoto zoom lenses, the greater it magnifies the error in the ground glass in the filter, the same would be with macro lenses. And because a large telephoto lens like the the depth of field is so narrow, which would exaggerate the error.

This is a problem the manufacturers have when they design a lens, canon and nikon user find there lens a far less accurate than Olympus lenses, because a lot of there lenses come from film camera lenses.

Sorry that you are having problems with your lenses, hope you get them sorted out ok.

All the best Dave
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
50-200mm on mFT timg Lens focus 4 10th April 2011 08:16 PM
50-200mm SWD forester Telephoto 11 31st August 2010 02:01 PM
Lens dilemma (Sigma 10-20mm V Oly 11-22mm) & (Sigma 70-200mm V Oly 50-200mm) jchallen Lens focus 19 10th November 2008 10:20 AM
40-200mm f2.8 FS sapper For sale or wanted small ads 0 19th May 2008 10:55 AM
New or used 50-200mm? beardedwombat Telephoto 24 20th December 2007 12:07 PM


All times are GMT. The time now is 04:31 PM.


© The Write Technology Ltd, 2007-2019, All rights reservedAd Management plugin by RedTyger