AX53 has backfocus error - only mine or by norm?!
 

Seems that things are becoming worse with the AX53 - seems this camera/series has a backfocus issue.
I now have the second copy because of the FW1.01 7 turn to focus from near to far error, and I'm sure the first also had a backfocus error.

On my current copy, I manually focus in full tele and then zoom out stepwise. Short after full tele sharpness disappears and is in the back, picture is blurred in the previous focused distance.
Going further to wide focus is coming back to the focused distance and everything seems fine.

I didn't fully check this with my first sample, but I had some blurred scenes I wondered why they are blurred.

What about your AX53?! Same behaviour?!

Think that Sony could also implement some more "factors" in the next firmware...

Re: AX53 has backfocus error - only mine or by norm?!
 

My AX53 seems to be reasonable in holding focus through repeated zooms from full wide to full tele. I zoomed in full set focus with touch focus and then zoomed full out. Text was still in focus as far I could tell as it was now very small for my eyes. Zoomed in and out several times and it seemed to hold its position. Firmware is 1.00

To my knowledge none of my earlier small Sony's are parfocal. They all loose focus with zooming and I haven't trusted them since way back to SR7 days. The SR7, SR11, XR500. CX700 all lost focus. The NX30U is better but I do not trust it either. That is why I took to using touch focus at the framing I wanted to use a long time ago. I think this approach lets the camera maximize depth of field around the point selected.

Ron Evans

Re: AX53 has backfocus error - only mine or by norm?!
 

It's also my experience that these small sony handycams don't have parfocal lenses, my cx730 is not parfocal either and displays the same behaviour like Roland has experienced. I would say this is "normal" for these type of camera's, if you want a parfocal lens you have to buy a camera with a better lens.

Re: AX53 has backfocus error - only mine or by norm?!
 

Focus in the "ends" is fine as described, but somewhere in the middle the cam looses focus.

Re: AX53 has backfocus error - only mine or by norm?!
 

As Noa says you have to buy a camera with a better lens. To get a 20x zoom with UHD and good lens you likely will be looking at the Panasonic AG-UX180 coming out this fall. Or with smaller zoom and UHD 30P the Sony PXW-Z150. All these cameras are close to 3 times the price of the AX53. My FDR-AX1 is 4 times the price and still does not have a parfocal lens but is 20 times zoom but has similar characteristics to the problem you are experiencing.

Ron Evans

Re: AX53 has backfocus error - only mine or by norm?!
 

I have to check my PXW-X70 for this but since I work the same way there and never found that problem with the X70 before I would say it´s fine there. It also seems not to happen always, but today I mudded many scenes because of this.
I also had this with my AX33 before, sometimes the recording was so unsharp that I thought I was drunken while focusing. Seems I have to give up zoom in, set focus and set the needed focal lenght...

Re: AX53 has backfocus error - only mine or by norm?!
 

...but parfocal or not, this could "easily" be compensated via firmware in these "electronic" lenses (if not already done) using a table with focus offsets for different focal lenght. The camera "sees" the focal lenght by a sensor in the lens. It displays the focal lenght with the indicator as also the distance.

But maybe tolerances and play of the lens are to high that a static compensation table would not help. This could also be the reason why I only see this issue sometimes (or often) but not always.

Re: AX53 has backfocus error - only mine or by norm?!
 

In any case, it makes this camera unusable for any work that requires the lens to stay in focus once it's locked. Not sure why it is not possible to make it parfocal but I"m sure Sony won't make any changes to the camera considering the clients who this camera is targeted to would not even have a clue what parfocal means.

Re: AX53 has backfocus error - only mine or by norm?!
 

The camera is intended for consumers with features to track focus in automatic etc. If you use these features I am sure they work just fine. But once focus is set in manual you cannot rely on it to stay in focus if zoomed. The old way of zoom in, focus then set framing just does not work. Sony approach would be to stay in auto and select the thing you want to stay in focus. The camera will then track that object. Works well to track children playing etc. Likely the intended market. It probably will not work well for birds flying in the trees. I like to have max depth of focus at any framing and as I said before this is best achieved by letting the camera control the focal point ( touch focus ) and exposure with AE shift. The engineers have worked out all this so the firmware I am sure will get good results for auto or semi automatic operation as I am sure was intended for this price point in the Sony range. If you really want full manual operation I am sure Sony would like you to buy a much more expensive camera like the FS5 which with a large zoom, batteries etc may set you back 10 times the cost of the AX53.

It will be interesting to check your X70 as I am not sure my FDR-AX100 is truly parfocal. I do not risk it and use it like all the other Sony's with touch focus and AE shift.

I have had a lot of good use out of my small Sony's by using the features in them to get the results I want.

Ron Evans

Re: AX53 has backfocus error - only mine or by norm?!
 

Ok, did another test filming an USAF chart and zooming stepwise in and out from about 10m. The AX53 is "parfocal corrected", so the focus stays on the target "by design", but as I supposed the focus is lost "sometimes" (a bit to often for my taste) on the way there and back. Seems this happens randomly, so actually really nothing to thrust. Without changing the focus the next time the focus is perfect at the same/similar focal lenght.
Maybe this is also a software error where a routine is "freezing" or not called correctly. I remember one time I had to take out the battery from my former AX33 to get rid of an enormous focus error while zooming that could easily be seen on the display.
On the other hand this could be a mechanical flaw...

By the way, the kid lens of the FS5 is known to be critical in many regards ;-)! Philip Joinston doesn't like it and reports some flaws on his site.

Re: AX53 has backfocus error - only mine or by norm?!
 

You just confirmed my understanding that you need to focus at the framing you want as you cannot trust the focus at full tele and then frame. Parfocal in my understanding means it stays in focus at all zoom position not just the ends. If it goes out of focus at any point it is not parfocal. If the camera is in auto the firmware can correct the focus as it zooms to a know characteristic. That is what the designers expected I am sure for a consumer camera.I think you may be expecting too much from a $1000 camera.

I think it produces a really nice image and mixes well with the AX100 I have on multicam shoots. The odd one out for me now is my aging NX5U.

Ron Evans

Re: AX53 has backfocus error - only mine or by norm?!
 

The design from lens and firmware (this seems to work together) is "kind of" parfocal.
When manually, correctly focused to a static target (USAF chart) in full tele (100% zoom factor) you can set any focal length including full wide (0% zoom factor) and the camera stays in focus without the need to change the focus manually nor by autofocus! That´s "parfocal".

Unluckily it happens randomly that the camera goes out of focus after a new setting of the zoom factor(e.g. 50%). Continuing with another setting of the zoom factor (30%) focus is correct again. Even going back to the same factor again (50%, checked using a scale below the chart) focus is dead on.

You can see that the focus is corrected by the camera itself while/after changing focal length/zoom factor since a short delay in focus correction is visible after fast zooming, so the lens by itself is not parfocal anyway, I hadn´t expected that either.

Seems that this software routine sometimes is not working correctly. I had one or two cases with my former AX33 were no focus correction was done at all, picture became totally blurred while zooming.
It went ok after taking of the battery for a moment. Beside that the AX33 randomly showed similar focus errors as described as my first AX53 did. I precisely focused in full tele and went back and later wondered why the picture wasn´t sharp. Never seen unsharp recordings with my X70 in MF yet, at least it was not noticeable. Will check that later.

Re: AX53 has backfocus error - only mine or by norm?!
 

The last camera I had that had a parfocal lens was my canon xh-a1, too bad Canon never made a affordable replacement.

Re: AX53 has backfocus error - only mine or by norm?!
 

Things becoming interesting here: from the Sony AX53 manual, UK .pdf version, page 114ff, Focus:

"HINT: It is easier to focus on the subject by moving the power zoom lever towards T (telephoto)
to adjust the focus, then towards W (wide angle) to adjust the zoom for recording.
When you want to record a subject at close range, move the power zoom lever to W (wide
angle), then adjust the focus."

-> parfocal behaviour - implemented by software as far as I found. Should work, unluckily "sometimes" not.

Re: AX53 has backfocus error - only mine or by norm?!
 

That particular paragraph has been in Sony manuals for years. I expect it just gets copied and it does make sense as when one normally comes wide from a focused tele the depth of field increases so minor focus changes are taken into consideration. The X70 with UHD option is more than 3 times the cost of the AX53 so I would hope it is better.When I got my NX5U 6 years ago it had a really bad backfocus issue and had the lens unit changed under warranty and has worked fine ever since.

Ron Evans