flange back problems with XF300

[Reinhard Kungel]

Hi together,

had the feeling for several times, that sometimes XF300 is not really sharp in picture.

Today I took several shots of the bavarian mountains and made some test. Back home in my editing-suite I was shocked to see, that some shots really are not sharp. Actually this is nearly impossible, because it is not a interchangable lens. Can´t believe it, but in fact, it is. By the way: it was a little bit cold, around minus 10 degree (Celsius), but I had the problems also at normal temperature (around 20 degree Celsius).

The way I made the test: Zoom-in into a tree, which is around 300 Meters away, then I focused manually (infinite looks sharp), zoom back, then I changed focus in steps from invinite down to one meter. The shot looks sharp betwen 1-2 meters. But actually the distance is around 300 Meters. Strange.

regards, Reinhard

[Steev Dinkins]

I also noticed focusing issue phenomena with the XF305. Here's some of the results of my testing:

XF305 Parfocal Accuracy Test on Vimeo

More detail is in this post:

In short, I am finding that the lens is not parfocal when aperture is open more than f3.2, and the ND filters make this problem worse. Aperture closed down past f3.2 essentially eliminated the issues.

My end conclusion was to double check all focusing if aperture open faster than f3.2.

[Chris Hurd]

Diffraction (soft focus) can occur not only at extremely
small apertures but open apertures as well, in some
conditions. Is it possible that's what you're running into?

[Reinhard Kungel]

Hi Chris,

used stop was around 4. Can´t imagine that this stop can cause problems.

regards, Reinhard

[Reinhard Kungel]

Hi Steev,

might be the same problem. Canon wants to check the camera. Hope to know more in some weeks.

Reinhard

[Jeff Lower]

I'd love to hear what they have to say once they get back to you about it.

[Reinhard Kungel]

Hi Steev,

what I really don´t understand: how can ND-Filters downgrade sharpness?
Canon is building high-end-lenses.

[Josh Dahlberg]

Hi Reinhard,

I'd be very interested to hear more on this. I've run into exactly the same problem a number of times - just the other day I zoomed in for critical focus on a subject 30m away, pulled wide for the shot, only to find in the studio the clip horribly out of focus. This happened a few times on the day, always outdoors with NDs engaged and f2-5.6 range.

Even with the 4" screen and magnification on it can be difficult to focus manually if you must stay wide. Very irritating.

I've owned a number of 1/3" cameras (XHA1, XL-H1, Z5 et al) and never run into anything like this...

[Reinhard Kungel]

Hi together,

today Canon Germany was calling me by phone. They told me, that they can´t find any focal problems.
They made test, inside and outside (minus 4 degree celsius) and everything went fine.

Thats all I can say for the moment.

regards,

Reinhard

[Steev Dinkins]

Originally Posted by Reinhard Kungel

today Canon Germany was calling me by phone. They told me, that they can´t find any focal problems. They made test, inside and outside (minus 4 degree celsius) and everything went fine.

Interesting. What I'm wondering is if they specifically tested for parfocal focusing accuracy throughout the entire focal length zoom range. You'd think that would be a given, but maybe not.

Perhaps, guaranteeing parfocal accuracy seems to be a challenge with this high of a resolution camera. Anyone have an EX1/EX3 to compare lens parfocal quality/behavior?

So far, I love the lens image quality itself, but the lack of constant aperture, lack of near focus consistency through zoom range, and questionable parfocal performance are all bummer points.

[Reinhard Kungel]

Today my XF300 came back. A letter from Canon Service tells, that they made several tests for a whole day, but couldn´t find any problems concerning focus. Not to draw wrong conclusions from, but the AF-Button of my XF300 now is switched from manual to automatic. I never use automatic-AF and I just hope, they didn´t made the test on AF-Mode.

[Steev Dinkins]

Originally Posted by Reinhard Kungel

I just hope, they didn´t make the test on AF-Mode.

Now that would be sadly comical. I think I'm going to do some further tests to really understand the behavior of parfocal performance, or lack thereof. I haven't had issues with shorter ranges of zooming. Its just going full telephoto, establishing focus, then going all the way wide, when at low f-stop that is not keeping focus.

Regardless, I'm so impressed with the image quality and highlight handling in post, I'm getting an XF300 as a camera B.

In short, I'm developing a very ingrained habit of using that magnification button to confirm focus, and not making as many assumptions as I did with the HVX200. The resolution is incredibly higher, and focus is more critical now than ever.

[Josh Dahlberg]

"Its just going full telephoto, establishing focus, then going all the way wide, when at low f-stop that is not keeping focus."

Yes that's a good definition of the problem Steve... things can go horribly awry when doing so! But this is really quite frustrating as it's standard procedure for many (inc. me).

It's quite hard to fathom how the Canon techs couldn't replicate this with your camera Reinhard, given that it's not subtle, it's really obviously out of focus when you do what Steve describes. Bet you wanted to pull your hair out when you got that letter.

I don't find magnification on the XF powerful enough to confirm focus - it works much more effectively on my 5DII.

[Reinhard Kungel]

"I don't find magnification on the XF powerful enough"

Hi Josh,

I confirm. You are right. With my EOS-550 it´s much more easier (higher factor).

[Don Palomaki]

A single frame grab at full zoom and full wide rather than the video might be easier to judge.

Did you send Canon a sample video illustrating the concern? Sometimes that helps them see what the issue is! A picture being worth 1000 words.