FS5: Anyone having parfocal issues with the Sony 18-110?

N

Newsguy

Well-known member
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. I’m not sure what to do at this point since I solely bought this lens for it’s ENG functionality, but if the “faux” autofocus parfocal isn’t doing it’s job, I may have to look for something else.
 
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
 
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?
 
legrevedotcom said:
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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Correct. So after composing, I have to turn the focus ring about an inch to catch focus again.
 
You scared me so I tested this afternoon. Spot on at 10 feet.
I Checked other distances today and its all good.
 
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LennyLevy said:
You scared me so I tested this afternoon. Spot on at 10 feet.
I Checked other distances today and its all good.
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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.
 
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?
 
LennyLevy said:
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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I’m sure yours is fine if the chart was on point. I did one test at about 10 feet and another at about 5. Each had the same issue. I hope it’s the lens and not the camera, as that will cause any parfocal lens to do this.
 
My friend bought a new FS7 Mark II and an 18-110 and the lens was clearly very soft on his camera, but fine on my FS7. We checked very carefully, so he sent the camera back to Sony and they said the camera & lens checked out fine. However they sent him another pair anyway because he insisted and they were fine. I'm not sure what the lesson is about that except stick to your guns until you get something that works from Sony. If you can of course check it with another camera.
 
Are you recording in 4k? The lens is perfectly par focal in 1080HD on the fs7, but in my experience the electronic correction that is applied there is not available in 4k ( on the fs7) and the lens becomes much less par focal and more like a DSLR lens in terms of zoom and refocus.
 
Wes. said:
Are you recording in 4k? The lens is perfectly par focal in 1080HD on the fs7, but in my experience the electronic correction that is applied there is not available in 4k ( on the fs7) and the lens becomes much less par focal and more like a DSLR lens in terms of zoom and refocus.
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For me it happens in both 4k and 1080. This is on the FS5.
 
Im sure I read somewhere .. that it came down to which one you got.. some were "more" par focal than others.. Does Sony actually claim straight out its a par focal lens.. ?
 
Donny 123 said:
Im sure I read somewhere .. that it came down to which one you got.. some were "more" par focal than others.. Does Sony actually claim straight out its a par focal lens.. ?
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This is what Sony says: "unwanted image shifts from issues including focus breathing and axial shift and focus shift while zooming are significantly reduced by Sony’s innovative SMO (Smooth Motion Optics) design and construction."
 
I've had '0' problems with parfocal performance in both HD and 4K. If both the lens and camera are on spec the 18-110 delivers. I'm getting exactly the same sort of results as outlined in this video:

https://www.youtube.com/watch?v=a1mx2AKjv2k

If you aren't getting the same sort of results take the whole thing back to Sony to get it sorted. Especially if it's under warranty.

It isn't the best lens in the world. It's a carbon composite construction body with metal internals like the new Fujinon MK series. For me for the price of the lens and the performance it delivers for that price has been a no brainer.

Chris Young
 
I use this lens on an FS5 and it is great. I have none of issues that have been described here. It has made my life my easier in the field.

One question: You did turn lens compensation 'off' correct? It should not be in the 'on position for this lens.
 
jc01108 said:
I use this lens on an FS5 and it is great. I have none of issues that have been described here. It has made my life my easier in the field.

One question: You did turn lens compensation 'off' correct? It should not be in the 'on position for this lens.
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Really? I wasn’t aware of this. Many of the reviews on this lens say it should be on, and some actually show before and after pictures of the pincushion and chromatic abberation being removed when turning it on. I’m sure those tests were done with the FS7 mkii since it’s the kit lens though. So on the FS5 correction should be off?
 
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