Calibrating Lens (Page 5): There was probably nothing wrong with the 2X Extender III. When you add one to a lens you have to adjust microfocus for the combination. I don't have an a...

mwsilvers Loc: Central New Jersey

Jolly Roger wrote:

I have two Canon cameras. 7D II and 1DX II. All my lenses are fine tuned on both bodies. Bought a Canon x2 TC MkIII three weeks ago, took it out with the 600mm a couple of weeks ago. All of those shots were back focusing by at least two feet (60cms). TC sent back to supplier and waiting for a replacement to arrive, hopefully in the next day or so.

There was probably nothing wrong with the 2X Extender III. When you add one to a lens you have to adjust microfocus for the combination. I don't have an a Canon Extender right now so I do not recall if Canon will store separate information for the lens with and without the TC attached. Success with a 2X TC can be very variable depending on the lens with which it's being used. Many people have indicated great success using the 2X III with lenses like the EF 70-200 mm f/2.8L IS USM II and the EF 200mm f/2.8L USM. Results with other lenses may not be as good.

gordone Loc: Red Deer AB Canada

It stores a separate MFA for the lens with the extender so you need to calibrate it with and without the extender

gordone Loc: Red Deer AB Canada

I have the 500 F4 ii and it works good with the 1.4x but not so great with the 2x. Both are series iii. The 300 F2.8ii seems to work good with the 2X iii. Varies between lenses and extenders and cameras. That's why you need a program like reikan to get real performance numbers out instead of a few subjective shots that some people use

TriX Loc: Raleigh, NC

mwsilvers wrote:

..I don't have an a Canon Extender right now so I do not recall if Canon will store separate information for the lens with and without the TC attached..

It will recoginize and store a separate correction for the lens plus ths extender.

mwsilvers Loc: Central New Jersey

TriX wrote:

It will recoginize and store a separate correction for the lens plus ths extender.

Thanks, I was pretty sure that was the case, but did not recall. I only had an extender for a short while and that was a year or more back. I bought the 2x extender III to use with my EF 70-200 f/4 L IS USM but it was a bad match and sent it back to B&H. Very soft and not fixable via micro focus adjustments. Since I rarely shoot at those longer focal ranges I couldn't reconcile the purchase of a top quality long telephoto lens. I recently acquired a Tamron 18-400mm for a general vacation walk around lens. While certainly a far from a top of the line optic, even the Tamron gives me much better images at 400 millimeters than the EF 70-200 L / 2x Extender III combination. For me it was a lesson learned. If I really want a quality lens in that focal range I will buy the Canon EF 100-400 or one of the third-party alternatives.

Jolly Roger Loc: Dorset. UK

mwsilvers wrote:

There was probably nothing wrong with the 2X Exten... (show quote)

Yes I'm aware of fine tuning the TC. My concern was that it was back focusing by such an amount (24" - 60cms or so). I doubt my two bodies would be able to adjust that amount. Spoke with the retailer and they said it sounds as if it has a fault. so they paid for it to be returned and are sending a replacement.

TomV Loc: Annapolis, Maryland

Jolly Roger wrote:

Yes I'm aware of fine tuning the TC. My concern was that it was back focusing by such an amount (24" - 60cms or so). I doubt my two bodies would be able to adjust that amount. Spoke with the retailer and they said it sounds as if it has a fault. so they paid for it to be returned and are sending a replacement.

Hi Roger, I cal'd my Minolta 600mm and used a distance of about 60 feet. A 2 ft error is substantial to compensate for at that distance, though I would have tried. But since you have the opportunity to try another copy then good luck to you.

Jolly Roger Loc: Dorset. UK

TomV wrote:

Hi Roger, I cal'd my Minolta 600mm and used a distance of about 60 feet. A 2 ft error is substantial to compensate for at that distance, though I would have tried. But since you have the opportunity to try another copy then good luck to you.

Hi Tom. I was waiting to get a bright day with no breeze, as I believe at 1,200mm (600 + x2TC) I need a distance of 50-60 yards / metres to do a correct calibration. But the 2ft plus kept niggling at me, finally decided to contact the supplier of the TC. I'm hoping to receive the new one tomorrow as I have the chance to go into a school building on Saturday and set up at the required distance, so that eliminates the weather constraints.

charlessl

Resolution charts provide a valuable way to evaluate lenses and focus. The advantages of a good resolution chart are many. They provide a quantitative measure of the resolution of a lens at many locations on the film plane, and some do it in red, green, blue, and black on a white background for both horizontal and vertical lines. You will find that the resolution at the edges may be different from those at the center for some lenses and that horizontal and vertical resolutions may differ.

Years ago I printed a chart measuring 36x24 inches with a state-of-the-art four-color press. Sets of lines are spaced to show resolutions of 20 to 160 lines per mm a 21 locations on the chart. The chart is photographed full-frame focused on a central plane and on two or three distances on front off and behind the central plane, typically the plane found by auto focus. The images are then examined on a computer. Email me for a description and instructions for use. The chart sells for $40, and is far superior, IMHO, to an $80 chart offered elsewhere online. Charles Sleicher, charles@sleicher.net