300mm Back Focus Query

[peak4]

A question for the house;
I was out last weekend for the first time in ages with the 300mm F2.8
For various reasons, I didn't take any bird shots, but managed some seriously out of focus shots of a Sea King Rescue helicopter over the Humber.
No real reason for the blurriness, as the shutter speed was high enough to freeze the rotors on some shots , but the chopper was still OOF.

I had a play that evening and also when I got back from work tonight and am convinced that the lens back focuses. This tallies with the background being in better focus than the helicopter.
I was using a 112mm Tokina UV filter as a front protector; This is a very good filter, and when used on the Tokina 300mm F2.8 manual lens, makes no discernible difference.
(I converted a Canon FD fit lens for 4/3s use a few years ago)
On the Oly lens though it seems to cause repeatable back focus. Why could that be?
I tried a series of test shots using the well known test chart at 45 degrees, with and without the filter and with/without converters.
I used the E-3 that I took at the weekend and also an E-620, with a Panasonic L10 as a control.

The results were quite odd

Camera/Converter.............With Filter...........................Without Filter
...........................EC-20.....EC-14.........None......EC-20.....EC-14........None
E-3..........................B...........B.......... ...B...............F..........OK.........OK/B-
E-620.......................B...........B........... ..B+.............F..........OK.........OK/B-
L-10.........................B...........B.......... ...OK/B-........F..........OK/B-.....OK

Sorry about all the full stops, it was the only way I could get the table to format

Where B = Back focus,
F = Front Focus
B- = a bit of back focus
B+ = Very pronounced Back focus

It looks looks a trip to Olympus might be in order as the lens seems only to be usable without a front filter and with EC-14
The small rear filter was fitted throughout.

Any ideas why this may be?

[David Morison]

Re: 300mm Back Focus Query

I don't use a front filter (didn't know you could get them that big!) but I always had indifferent results with the EC20 on my 300mm, intermittent back-focus for some reason. The EC 14 still requires -2 with AF adjust but at least is consistent and I am very happy with the results. Let us know the outcome of your investigations because the problem is very baffling.

David

[peak4]

Re: 300mm Back Focus Query

I don't use a front filter (didn't know you could get them that big!) but I always had indifferent results with the EC20 on my 300mm, intermittent back-focus for some reason. The EC 14 still requires -2 with AF adjust but at least is consistent and I am very happy with the results. Let us know the outcome of your investigations because the problem is very baffling.

David

Good quality 112mm filters are hard to come by; B+W do make one but only in 1.5mm pitch which doesn't fit any modern lenses I've heard of.
Heliopan used to list one, but I've never tracked one down. I found the Tokina one on ebay just after I'd converted the 300mm FD lens to OM mount so I could use it on 4/3s.
I do find it annoying that one needs to dial in any correction at all with a lens, particularly a flagship one.

I spoke to Oly in Germany today, who seemed more concerned that I would use it with a none Olympus filter, than it misfocusing with or without one.

They advised me to send it in for repair, so I'll wait until it comes back from its Portugese holiday and see how it performs then. I'll be sending in the E-3 as well since the hot shoe contacts have started to corrode; no idea why as its never been stored anywhere damp.
It lives, along with my lenses, in a large cocktail cabinet with regularly refreshed silica gel sachets; I cook them in a low oven as soon as they change colour (the sachets, not the lenses .)

Whilst I would dearly like an E-5, I don't see why I should have to buy one to get a five grand lens to focus correctly.

[peak4]

In Praise of Olympus Service

Just an update for those with 300mm lenses who may have been reading the thread originally.
I've had a thorough report back from Olympus in Japan, where the lens currently resides.
It seems that the lens itself is within tolerances, but seriously back focuses with a 112mm front filter on. This will always be the case unfortunately, so I'll just need to take extra care with the front element. It does seem a little odd that there is a 112mm thread provided that can't be used for a filter.
More unfortunately though, it will always mis-focus with a tele-converter fitted.
Olympus can adjust it to focus correctly with either converter but then it would be off with the other, or if none were fitted. I can't help feeling it's a bit of a failing for a flagship lens.
They did make the offer of shipping both my converters and my E-620 off to Japan at their expense so they could set up the body for all three scenarios. It didn't seem worth putting them to that effort when I should be able to accomplish the same at home with a couple of hours labour myself.

Overall I can't praise Olympus service highly enough. They have done all that could be reasonably expected of them, and more besides.
My E-3 had a corroded hot shoe mount changed under warranty, even though the camera is over 2 years old (they swapped the whole top plate), my 14-54 was adjusted and the 11-22 had its transport mechanism replaced. I didn't even know anything was wrong with the two smaller lenses and just included them for a check up as there was room in the Doskocil case.
I'd left the grip fitted to the E-3; they changed the main board in that as well even though I'd not reported the battery shutdown error with it.

The two small lenses, the grip and E-3 were returned serviced and mended in a week, with prompt and helpful updates from Karina at Oly UK.

This may all be because I'm still a member of the E-Master club, though this is due to be superseded soon. I'll certainly consider signing up for the replacement scheme.

It looks like I'll need to start saving for an E-5 if I want a weather resistant 300mm+ setup .

Anyone want to buy a 112mm B+W filter to start the E-5 fund?

[francois]

Re: 300mm Back Focus Query

Thanks for the update. Disappointing story considering the price of that lens and its flagship status. Have Olympus said whether all 300mm suffer from this, or is it just yours?

[David Morison]

Re: 300mm Back Focus Query

On my E5 there is no difference between the naked 300 and 300 + EC14, both are AF adjust -2 which totally acceptable. Even multi-million pound scientific instruments need calibrating very frequently (although this is mainly automatic) so to have my set-up needing to be calibrated once only is excellent.

David

[peak4]

Re: 300mm Back Focus Query

David, This one was reasonable with the EC-14, just a bit off when I tried it with the focus chart; to be fair when its got the converter on it will be used at long distance, so the DOF will help correct any variation in focussing accuracy.

It was completely unusable with the EC-20 though. Oddly it back focused with the 112mm filter on, but front focused without.
I'm sure I will be able to tune things on the E-620 when I get the lens back.

In reality, if the weather is bad enough to need the waterproofing of the E-3, the likelihood of getting good photos at 600mm is probably slim anyway.

The way Olympus service have treated me in all of my dealings with them, does encourage me to seriously think about saving up for an E-5.

[Melaka]

Re: 300mm Back Focus Query

Thank you for your observations. I'm not entirely happy with the focus of my 300mm with the EC14 and have had disappointing results with the EC20. As I understand it both the E5 and E620 have AF focus adjust. Is this something you have to do individually for each lens/converter combination or is there a standard setting one can apply? Advice on what to do and how to do it (aimed at the simple minded!) would be much appreciated.

[sapper]

Re: 300mm Back Focus Query

I would be interested in this too.

[Ian]

Re: 300mm Back Focus Query

I seem to be lucky in that I have not noticed any focusing issues with our 300 f/2.8s - with or without EC-14s or EC-20s.

I have no idea if you can focus calibrate a lens with a converter as well as the lens without the converter - so I will have to try and find out!

Ian

[Daveart]

Re: 300mm Back Focus Query

Hi I believe that you can focus adjust with ec20 or ec14 with a particluar lens combination, and it only adjusts with that combination that you focus adjust with, and it is serial number detemined, ie you could have two ec20's and focus adjust with the one on a particular lens serial number and one not and the adjustment adjusts with that particular setup. Thats the way I have read it with the manual. Hope this makes sense.

Dave

[Ian]

Re: 300mm Back Focus Query

Hi I believe that you can focus adjust with ec20 or ec14 with a particluar lens combination, and it only adjusts with that combination that you focus adjust with, and it is serial number detemined, ie you could have two ec20's and focus adjust with the one on a particular lens serial number and one not and the adjustment adjusts with that particular setup. Thats the way I have read it with the manual. Hope this makes sense.

Dave

That's the theory - the lens serial number is the key to all this. The thing I'm not sure of is whether the system can record profiles for the same lens without a converter and with a converter. It should in theory...

Ian

[peak4]

Re: 300mm Back Focus Query

That's the theory - the lens serial number is the key to all this. The thing I'm not sure of is whether the system can record profiles for the same lens without a converter and with a converter. It should in theory...

Ian

I'll let you know when it comes back and I have a go with the E-620.
I'm still waiting to see if I get charged for the investigation.

[David Morison]

Re: 300mm Back Focus Query

Both the E5 and E30 allow you to record settings for the lens and lens/TC combos separately. When a lens or lens/TC combo is attached the camera automatically chooses the relevant AF adjust setting that has been previously registered. I think this works for all 4/3rds lenses, not just Olympus, I know it certainly works for Sigma, Leica and Panasonic but obviously not legacy or any lens requiring a converter ring.

David

[Daveart]

Re: 300mm Back Focus Query

Hi I think that the EC 14 and EC20 have an ID serial number which would make sense as one could be slightly out from another so it detects the one that has been adjusted for. I did read somewhere That you could calibrate a lens and an EC14 and if you changed the EC 14 of a friends same with that same lens it would not use the recalibrated setting but the default one.

Dave