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    Anyone having parfocal issues with the Sony 18-110?
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    I have used this lens on a few different types of shoots recently. When looking at my footage in post I noticed some softness during a sit down interview where I know I properly focused on the subject. After seeing this I decided to to a little test in the field. I was open at F4, I zoomed in, grabbed focus, and zoomed out. Even on my monitor the subject looked a tad soft. So I focused from distance like I would with a photo lens. When checking both shots in post, it is clear that the shot where I focused from distance is the sharp one. The shot where I got focus on the lashes and zoomed out was visibly soft.

    Has anyone else had this issue? I have a friend with an FS7 who says his medium shots are consistently soft with this lens, and he also uses this focus method. Iím not sure what to do at this point since I solely bought this lens for itís ENG functionality, but if the ďfauxĒ autofocus parfocal isnít doing itís job, I may have to look for something else.


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    Senior Member legrevedotcom's Avatar
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    Thats because its not really parfocal... but its very close to being.


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    #3
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    No not to date... yet, touch wood. I've shot many interviews, live stage shows and sports events and never had an issue with focus, the lens has always performed as a parfocal lens. Check with another 18-110 if you can and if that is also out it may actually be the camera needs adjustment.

    As these lenses have no back focus adjustment it is imperative that the sensor to flange distance is even at each of the three "IM" washer locations. The adjustment of these IM washers assures correct parallel alignment of the sensor relative to the lens mount, or so I have been informed. This adjustment I was further informed must be pretty spot on for the inbuilt lens correction to work 100% and this includes its back focus. I have had no personal experience of any focus issues but the question did crop up when I was talking to a Sony tech when I asked how was back focus achieved. Look at the two following images and you will get an idea of how this arrangement works. You will see these IM washers listed. I have since found out that these washers come in thicknesses ranging from 0.05mm to 0.495mm. From what I gather the thickness isn't important and various thickness can be used as long as as a parallel state of affairs can be achieved.

    Chris Young

    IM1.jpgIM2.jpg


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    Senior Member legrevedotcom's Avatar
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    Ah... I need to correct myself. It seems its parfocal in the way that its electronically help... so, not optical parfocal. When you travel the zoom, the focus has to be ajusted by the camera... this apparently has a slight lack, and probably most noticable when you rack it. But I take it your shots are zoom in to focus and then zoom out to compose?


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    Senior Member Bern Caughey's Avatar
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    Not sure this applies to 18-110mm, but the 28-135mm is parfocal except near it’s minimum focus distances.


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    Quote Originally Posted by legrevedotcom View Post
    Ah... I need to correct myself. It seems its parfocal in the way that its electronically help... so, not optical parfocal. When you travel the zoom, the focus has to be ajusted by the camera... this apparently has a slight lack, and probably most noticable when you rack it. But I take it your shots are zoom in to focus and then zoom out to compose?
    Correct. So after composing, I have to turn the focus ring about an inch to catch focus again.


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    #7
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    No issues that I've noticed with my 18-110. I'm loving going back to punch in, focus and pull out.
    Ben Giles BFE BAFTA

    www.matobo.co.uk

    @MatoboLtd


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    You scared me so I tested this afternoon. Spot on at 10 feet.
    I Checked other distances today and its all good.
    Last edited by LennyLevy; 02-16-2018 at 12:47 AM.


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    #9
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    Quote Originally Posted by LennyLevy View Post
    You scared me so I tested this afternoon. Spot on at 10 feet.
    I Checked other distances today and its all good.
    I’m glad your lens is ok. Mine is not. I ran some tests today. I recorded the actual act of zooming in and grabbing focus. I zoomed out to a medium shot, and then re check focus. When on a person, the focus shifts to the ears every time. I then refocus to get the lashes back in focus from that distance, but when I zoom back in, the lashes are out of focus. It’s basically behaving like a photography lens right now. The further I zoom out, the more I need to roll focus to stay keep the original focus point. I’m gonna call support tomorrow to see what my options are.


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    You got me scared again because I didn't try it with a person only with a chart. I'm going to test the damn thing again but can't do it for a few days. What distance are you testing at?


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