Help on lens calibration and focus test

[Encorez]

Hi CSers,

This is my first thread in a discussion section so if there is anything I did that's against the rules, just let me know and I will edit it immediately!

I had been having focus problems on my Nikon 50mm f1.8g. Plus, I recently purchased a Sigma 17-50mm f2.8 which (based on what I read) is notorious for focus problems so I looked up a bit on calibration and did a simple test myself.

What I did was,
- Set my D3200 on my tripod facing the focus test chart on the wall (beside the window at about 1pm)
- Shot 3 shots (RAW) using live view and 3 shots with the viewfinder
- 2 sec self-timer at ISO 100 using center focus point
- Did this for each of my 3 lens
(1)50mm f1.8g Nikon
(2)18-55mm f3.5-5.6 kit lens
(3)17-50mm f2.8 Sigma
- Reduced sharpening in Lightroom to 0

and here are the results I got,
(I only posted 1 live view and 1 viewfinder shot for each lens, but there are more samples in my flickr album - YH, on Flickr)

- Nikon 18-55mm f3.5-5.6 at 48mm f5.6
Live view - https://farm2.staticflickr.com/1602/23720951754_9a03f64f42_o.jpg
Viewfinder - https://farm2.staticflickr.com/1631/24266644931_221d405820_o.jpg

- Nikon 50mm f1.8g at 50mm f1.8
Live view - https://farm2.staticflickr.com/1699/24349119875_4e7c52b795_o.jpg
Viewfinder - https://farm2.staticflickr.com/1470/23981336769_e62c9a09e7_o.jpg

- Sigma 17-50mm f2.8 OS DC HSM at 50mm f2.8
Live View - https://farm2.staticflickr.com/1707/24240917042_ae79a9f311_o.jpg
Viewfinder - https://farm2.staticflickr.com/1689/23722324473_3ab8dd01d9_o.jpg

I am interested in trying out portraiture so sharp focus is really important. The 50mm prime probably needs re-calibration but I am not sure about the Sigma. It seems to have a tiny bit of rear focusing although I don't know if that tiny bit really matters in practice. I am hoping to get some of your advice. Should I bring it down for calibration?

 

[Octarine]

What I did was,
- Set my D3200 on my tripod facing the focus test chart on the wall (beside the window at about 1pm)[...]

The focus test chart I know is to be setup on a flat surface, camera pointing at 45 degree angle at the sheet.
http://bobatkins.com/photography/technical/focus_testing.html

I am interested in trying out portraiture so sharp focus is really important.

It is also important to know how the focus works and which factors will impact it. Otherwise you might start hunting ghosts.
On the other hand, in studios the portraits are usually taken with smaller apertures, focusing errors would have little impact due to deeper DoF.

 

[sadper]

ur camera is beside the window or the chart? Is both ur camera and focus chart parallel to each other. If both answer is yes then the picture took cannot be use

 

[Encorez]

The focus test chart I know is to be setup on a flat surface, camera pointing at 45 degree angle at the sheet.
http://bobatkins.com/photography/technical/focus_testing.html

Hi Octarine, thanks for the reply. The test I followed was this one https://photographylife.com/how-to-quickly-test-your-dslr-for-autofocus-issues but I think I will try again with the link you posted.

ur camera is beside the window or the chart? Is both ur camera and focus chart parallel to each other. If both answer is yes then the picture took cannot be use

Hi, I set up the camera beside the window with the chart on the wall adjacent to the window. The reason was so that there will be enough light for the phase focus to be accurate.

 

[Light Machinery]

Hello Encorez. I have looked through the pics of the test target you posted

1) The 50mm f/1.8 focus is off by quite a lot when comparing live view (contrast AF) vs view finder (phase AF) shot.

2) The Sigma focus is also off by but its much lesser when compared to the 50mm f/1.8. Usually it is always the wide aperture lenses that suffers the most with back / front focus issues.

3) The 18-55mm is as good but with the small aperture lens it will usually mask any back / front focus issues that the body may have.

3) What you need is a set up like this to know if your lens is back or front focused.

https://nikoneurope-en.custhelp.com.../51633/~/how-to-use-the-af-fine-tune-function

4) With a flat target as you have shot you will not be able to see / judge if the camera / lens combo is back or front focused.

5) Here is how it looks like when for a well centered AF

Well centered after AF fine tune by Hou Leong Chan, on Flickr

6) Also please do the test in under natural light as mixed light / florescent / incandescent light will have an effect on the phase AF accuracy. Some lenses / body combo will AF at different points (front or back focuses) under mixed light / florescent / incandescent light.

7) The D3200 does not have any AF fine tune feature. Collect all the shots that shows the AF problem & go down to the respective service centers together with the lens & camera body & explain to the service representative / tech on the AF problem that you have with the lens / body. Check the AF again when you collect the lens / body from the service center.

All the best in your endeavor in sorting out the AF issues.

 

[trenzterra]

Just wondering, does Nikon service centre provide lens/body calibration service? Is it free if still under warranty?

 

[sammy888]

Just wondering, does Nikon service centre provide lens/body calibration service? Is it free if still under warranty?

hahahahah.......

 

[trenzterra]

hahahahah.......

Maybe I'm asking a stupid question, but I come from a Samsung NX system where when I went to the service centre to ask for pixel mapping, they had no idea what a hot pixel was. So I didn't want to assume and wanted confirmation that Nikon SC isnt that stupid and is able to do such a service before I switch over to the Nikon system.

 

[Light Machinery]

The last time I went to NSC, the service representative had no problem understanding the problem that I had with my camera body / lens problem.

They had the camera / lens for about an hour. Calibration was completed & it met my expectations.

It was done foc, as the body was under warranty.