Calibrate Sigma 18-35mm (Nikon)

Started 3 months ago | Questions
mohxinn Regular Member • Posts: 131
Calibrate Sigma 18-35mm (Nikon)

Hi!

I know there are many thread discussing autofocus problems and each describes different ways on how to calibrate it using the Sigma dock.

In the dock, there are 4 distances for which one can input fine tune values. My question is:

Should I input values (update lens) one by one for each FL and distance combination before moving to the next? Or all at once at the end?

Should I measure all FLs for one distance and then move to the next distance? (go top to bottom)

Or should I measure all distances for one FL? (go left to right)

Is it OK to skip infitiy?

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SushiEater
SushiEater Veteran Member • Posts: 9,615
Re: Calibrate Sigma 18-35mm (Nikon)

mohxinn wrote:

Hi!

I know there are many thread discussing autofocus problems and each describes different ways on how to calibrate it using the Sigma dock.

In the dock, there are 4 distances for which one can input fine tune values. My question is:

Should I input values (update lens) one by one for each FL and distance combination before moving to the next? Or all at once at the end?

Should I measure all FLs for one distance and then move to the next distance? (go top to bottom)

Or should I measure all distances for one FL? (go left to right)

Is it OK to skip infitiy?

First you determine values at MFD for all 4 FLs. Actually it is about close to MFD but not exactly MFD. Input them and write to the lens. Now move on to the next distance. Repeat.

Are you shooting at Infinity? If not, skip it. But first determine where infinity is. 18-35mm has huge DOF so settings for Infinity would be very difficult to measure.

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OP mohxinn Regular Member • Posts: 131
Re: Calibrate Sigma 18-35mm (Nikon)

Thank you for answering. I did the calibration, as you suggested, by tuning all FLs for a given distance, inputing them in dock and moving to next distance.

Resilts look good so far. I will test more and report again.

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OP mohxinn Regular Member • Posts: 131
Re: Calibrate Sigma 18-35mm (Nikon)

I tested more and it seems that focus way off for distances > 0.5m but there is no option oto calibrate for distance greater than 0.5m. Do I need to calibrate the infinity block to get focus right?

Also I read in some other threads that one has to start from infinity and then go to smaller distances?

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SushiEater
SushiEater Veteran Member • Posts: 9,615
Re: Calibrate Sigma 18-35mm (Nikon)

mohxinn wrote:

I tested more and it seems that focus way off for distances > 0.5m but there is no option oto calibrate for distance greater than 0.5m. Do I need to calibrate the infinity block to get focus right?

Also I read in some other threads that one has to start from infinity and then go to smaller distances?

Everything you said does not make any sense. What do you mean there is no option to calibrate?

Connect the lens and start software. Capture the screen of Focus calibration and post here.

Also, what do you use to calibrate? Show your target and setup.

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Kazmarov Regular Member • Posts: 146
Re: Calibrate Sigma 18-35mm (Nikon)

It is difficult to understand your issue if you are using the Sigma Dock. Perhaps you could rephrase?

For the 18-35, the dock has four distances along the columns and four zoom levels. You have to calibrate for the minimum one first and move down the focal lengths, then select the next distance & adjust until you get to & complete the infinity column. If your lens is anything like mine it should show infinity at around 35-40 metres at 35mm focal & f/1.8.

Re your final query, Sigma UK tech recommend starting from the minimum distance - I cannot comment on the statement you quote from other forums.

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OP mohxinn Regular Member • Posts: 131
Re: Calibrate Sigma 18-35mm (Nikon)

Kazmarov wrote:

It is difficult to understand your issue if you are using the Sigma Dock. Perhaps you could rephrase?

For the 18-35, the dock has four distances along the columns and four zoom levels. You have to calibrate for the minimum one first and move down the focal lengths, then select the next distance & adjust until you get to & complete the infinity column. If your lens is anything like mine it should show infinity at around 35-40 metres at 35mm focal & f/1.8.

Re your final query, Sigma UK tech recommend starting from the minimum distance - I cannot comment on the statement you quote from other forums.

Sorry for not being clear. I meant that even after calibration focus is still inaccurate when the subject is greater than 0.7m (not 0.5m I checked again). I check the lens scale after taking a picture to get the subject distance.

The four distances to calibrate on the dock are 0.28m, 0.35m, 0.5m & Infinity. I have no values in the last column (infinity distance) as I don't plan on shooting at infinity.

Could it be that I need to put values in the last column for accurate focus for subject distance > 0.7m?

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SushiEater
SushiEater Veteran Member • Posts: 9,615
Re: Calibrate Sigma 18-35mm (Nikon)

mohxinn wrote:

Kazmarov wrote:

It is difficult to understand your issue if you are using the Sigma Dock. Perhaps you could rephrase?

For the 18-35, the dock has four distances along the columns and four zoom levels. You have to calibrate for the minimum one first and move down the focal lengths, then select the next distance & adjust until you get to & complete the infinity column. If your lens is anything like mine it should show infinity at around 35-40 metres at 35mm focal & f/1.8.

Re your final query, Sigma UK tech recommend starting from the minimum distance - I cannot comment on the statement you quote from other forums.

Sorry for not being clear. I meant that even after calibration focus is still inaccurate when the subject is greater than 0.7m (not 0.5m I checked again). I check the lens scale after taking a picture to get the subject distance.

Is it consistently inaccurate? Are you running the test outside or inside in the low light?

The four distances to calibrate on the dock are 0.28m, 0.35m, 0.5m & Infinity. I have no values in the last column (infinity distance) as I don't plan on shooting at infinity.

Could it be that I need to put values in the last column for accurate focus for subject distance > 0.7m?

The infinity is not just infinity. It has a range. You need to look at the software screen to see where red line is sitting at infinity. Then go outside and focus on something so the white line in your focus distance window matches the software screen. The you have to find your target like a building with a bunch of windows  or a very long brick wall or a fence and make sure you focus at the point at 45 degrees and the be at the distance that the white line is the same as before sitting on the part of infinity range. But it will only work if you have consistent focusing.

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OP mohxinn Regular Member • Posts: 131
Re: Calibrate Sigma 18-35mm (Nikon)

The subjects at 0.7m and greater are consistently out of focus. I will do calibration and add values for infinity distance. It might be that this has affect on the previous range (0.4 - 0.7m) in the dock.

Regards,
Mohsin
Flickr: https://www.flickr.com/photos/90692793@N03/

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SushiEater
SushiEater Veteran Member • Posts: 9,615
Re: Calibrate Sigma 18-35mm (Nikon)
1

mohxinn wrote:

The subjects at 0.7m and greater are consistently out of focus. I will do calibration and add values for infinity distance. It might be that this has affect on the previous range (0.4 - 0.7m) in the dock.

Regards,
Mohsin
Flickr: https://www.flickr.com/photos/90692793@N03/

Out of focus is obvious since you are not satisfied but how out of focus? Is it always front focus at different measurements or front focus and back focus. If it is always in the same direction you might be able to do something or not but if it is front one time and back another then your lens might be defective. Adding something to Infinity is not going to fix your problem because if it did it would effect all values but that is usually not the case. All manufacturers recommend starting with the closest value. If infinity value effected the previous values it would be impossible to calibrate anything.

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Kazmarov Regular Member • Posts: 146
Re: Calibrate Sigma 18-35mm (Nikon)

OK. I think Sushieater covered the subject in his post so not a lot to add.

If after the infinity calibration,  the focus is still in-accurate under the same lighting & target ( by this I mean that you get the same degree of focus discrepancy in multiple "runs" for the same distance (e.g. at 0.9m , 3m , 5m etc)) or If it is inconsistent at the same distance (e.g for different runs at 3m you get varying degrees of in-accuracy) then I am afraid you will need to make contact with Sigma.

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OP mohxinn Regular Member • Posts: 131
Re: Calibrate Sigma 18-35mm (Nikon)

I was calibrating for D5300 but then changed to a D5600 for touch screen capabilities. I managed to get the lens to autofocus quite accurately now on my D5600. I just had to be patient. What worked for me was to calibrate and use in real-life scenarios. Required many iterations before I got consistent and accurate focus. Furthermore PDAF can give varying results. So I took at least 10 shots before settling on a fine tune value.

Just for info, I used Spyderlenscal for calibration.

Thank you so much for your support and help. Really appreciate it!

Loving this lens. Exceptional in everyway! Truly matches quality of my D850 in good light situations.

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CMCphoto Junior Member • Posts: 27
Re: Calibrate Sigma 18-35mm (Nikon)

I'm glad to hear its treating you well.

Just to satisfy my own curiosity, does it focus accurately both using the center AF point and the farthest outside AF point?

I had the lens and loved the image quality, but I even with calibration I could never get the outside and middle focus points to work at the same time.

Many thanks!

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