How can a lens on a mirrorless system front focus?

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

 

[JimKasson]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

Focus shift? I don’t have that lens yet, so I can’t comment from experience. Interesting that it happens with both CDAF abd PDAF.

 

[Rich42]

Faulty lens? Need to update firmware?

When you focus manually, how are you confirming focus? Just the appearance of the image in the viewfinder? Or with one of the focusing aids?

Rich

 

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

Focus shift? I don’t have that lens yet, so I can’t comment from experience. Interesting that it happens with both CDAF abd PDAF.

 

[Zorki-6]

Faulty lens? Need to update firmware?

When you focus manually, how are you confirming focus? Just the appearance of the image in the viewfinder? Or with one of the focusing aids?

Rich

Hi Rich. No firmware for the lens as yet but if it's faulty, I'm struggling to understand the mechanism that would see it front focusing so consistently.

In MF it's fine whether I make a judgement using the EVF/screen or focus peak highlights (low).

I've looked back at any frame I've taken close up using AF-S since I got the lens and none have correct focus.

 

[Rich42]

Faulty lens? Need to update firmware?

When you focus manually, how are you confirming focus? Just the appearance of the image in the viewfinder? Or with one of the focusing aids?

Rich

Hi Rich. No firmware for the lens as yet but if it's faulty, I'm struggling to understand the mechanism that would see it front focusing so consistently.

In MF it's fine whether I make a judgement using the EVF/screen or focus peak highlights (low).

I've looked back at any frame I've taken close up using AF-S since I got the lens and none have correct focus.

Strange, the Focus Peaking is derived from the AF mechanism. If it's correctly indicating focus, that should be controlling the lens accurately. Maybe the focus mechanism in the lens is not responding the way it should.

Rich

 

[John Crowe]

Do you have a local store to try a different lens?

 

[Zorki-6]

Do you have a local store to try a different lens?

I'm out of luck there. The 35-70 isn't available here except as part of the bundle with the 50S II and there are pre-order waiting lists for that, so it's unlikely anyone will have one in stock. I think my best bet is to get on to Fujifilm support as the more rigourously I test this the clearer it becomes that it's a fault of some kind, either hardware or (hopefully) software.

 

[Zorki-6]

Faulty lens? Need to update firmware?

When you focus manually, how are you confirming focus? Just the appearance of the image in the viewfinder? Or with one of the focusing aids?

Rich

Hi Rich. No firmware for the lens as yet but if it's faulty, I'm struggling to understand the mechanism that would see it front focusing so consistently.

In MF it's fine whether I make a judgement using the EVF/screen or focus peak highlights (low).

I've looked back at any frame I've taken close up using AF-S since I got the lens and none have correct focus.

Strange, the Focus Peaking is derived from the AF mechanism. If it's correctly indicating focus, that should be controlling the lens accurately. Maybe the focus mechanism in the lens is not responding the way it should.

Rich

That's the only explanation that makes sense to me, but it could conceivably be a software issue that might be rectified with firmware. I'll contact Fujifilm tomorrow and see what they suggest.

 

[JimKasson]

Strange, the Focus Peaking is derived from the AF mechanism.

In my tests, which in this case aren't entirely definitive, the focus peaking appears to be done by differentiating, rectifying, and thresholding the scan lines in the finder image.

 

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

Not the greatest chart or conditions but it's so pronounced that it does the job. Wide open (f5.6) and at 70mm, but the problem occurs at all focal lengths.

View attachment c0647edcf22f4c1a81d94996b9bcc401.jpg
AF-S, single point

View attachment cdfd59f3ebd348feb671c9e03f850760.jpg
AF-S, zone

View attachment cb04ef06cac54d708728cfb2812a4f73.jpg
MF - I focused slightly behind

View attachment cbfbe9a3cafb439f909de19a150da108.jpg
What I'm dealing with in the field. Focus was attempted on the left-most bolt, consistently front focusing



Edit: apologies, I have Lightroom set up to strip out EXIF, will reupload if anyone's interested in the EXIF.

 

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

Not the greatest chart or conditions but it's so pronounced that it does the job. Wide open (f5.6) and at 70mm, but the problem occurs at all focal lengths.

View attachment c0647edcf22f4c1a81d94996b9bcc401.jpg
AF-S, single point

View attachment cdfd59f3ebd348feb671c9e03f850760.jpg
AF-S, zone

View attachment cb04ef06cac54d708728cfb2812a4f73.jpg
MF - I focused slightly behind

View attachment cbfbe9a3cafb439f909de19a150da108.jpg
What I'm dealing with in the field. Focus was attempted on the left-most bolt, consistently front focusing

Edit: apologies, I have Lightroom set up to strip out EXIF, will reupload if anyone's interested in the EXIF.

Just to demonstrate that in zone AF the camera seemingly knows exactly where to focus but there's perhaps something mechanical going on in the lens that's resulting in the misfocus. I've never seen anything like this with mirrorless, a strange one for sure.

 

[7seven7]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S......... What could be going wrong here?

It's absolutely fine when manually focused.

Hi Zorki,

This 35-70mm is a new model,

so doesn't it need a firmware update of your 3 cameras to work fine ?

my 0.02

 

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S......... What could be going wrong here?

It's absolutely fine when manually focused.

Hi Zorki,

This 35-70mm is a new model,

so doesn't it need a firmware update of your 3 cameras to work fine ?

my 0.02

That was my first thought, but there isn't any firmware available and the 35-70 has been around a while now. The 35-70 is also bundled as a kit lens with the 50S II so you'd hope they'd work together out the box. I spoke to Fujifilm and we're talking about a repair even though I'm inside the window for an exchange, because I'd have to return the camera and lens with no indication of how long I'd have to wait before they have stock.

 

[Zorki-6]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

The lens has a fault, Fujifilm aren't able to replace it because there's no stock and there are no parts currently available to repair it, so offered any GF lens in their range as a rental until it can be rectified. While I might be a little frustrated with the QC issues I can't complain about the customer service.

 

[SrMi]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

Focus shift? I don’t have that lens yet, so I can’t comment from experience. Interesting that it happens with both CDAF abd PDAF.

It does have a touch of focus shift but this is something else. I'm auto focusing wide open (AF-S) and it's consistently front focusing such that the subject is well and truly in the OOF area. We're talking an inch out when shooting near its minimum focusing distance.

How do you do AF?

Fuji cameras that I have tested have issues with BBF and AF-C (focus jumps after releasing the focusing button).

 

[highdesertmesa]

When close focusing with my new 35-70mm I can't get anywhere near accurate focus using AF. It's consistently front focusing by quite some distance on my 50S II, 50R and 100S.

Excuse my technical illiteracy, but this doesn't make a great deal of sense to me. Surely the camera uses information from the sensor to determine focus, unlike with a DSLR where micro-adjustments are often necessary? What could be going wrong here?

It's absolutely fine when manually focused.

If you have front focus on mirrorless near MFD, it's almost always a firmware issue. Canon had a similar front-focus issue at MFD with their RF 70-200 f/2.8 when it first came out, and it was fixed by a firmware update. Getting Canon to recognize the issue was another story.

You need to find someone else with the same combo, and see if they confirm the same issue. If so, then a firmware fix will be coming if you and others can get Fujifilm to confirm the issue. If no one else has the same problem, return the kit since you don't know for sure if it's the lens at fault.

The reviews so far say the sharpness near MFD is really bad for this lens – I'll bet it's because there is a front-focus issue with all of them and none of the reviewers bothered to check for front focus.