Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Started May 18, 2014 | Discussions thread
BobORama Senior Member • Posts: 2,559
Re: Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Trevor G wrote:

Here's the other, easy to see shot which shows the skew to the DOF:

Open at max size and scroll from one side to the other while watching the DOF shift as you scroll - it's closer one side than the other, and also a different depth from side to side.

Also if 19 of your 20 lenses have this issue, perhaps the issue is with the camera body.

Both sold. It didn't matter - they all showed the same relative skew.

Do all of the lenes have a right - left focus shift? And with a top to bottom shift?

It's not the camera. Betcha.

You are right, its the photographer.

In this shot, if you look at the vertically oriented white lines on the board and take them as perspective lines, their axis of symmetry is shifted to the right ( same issue, by the way, as the train station. )

You did not shoot the board straight on.   But aimed towards the left slightly.   This creates a focus zone which is lower on the left side and higher on the right.

So scan across the image and look at the white lines.   The pattern should look like, with left and right leaning lines indicated as well as the actual vertical ( which in this case is somewhere in the knobs: )

/ / / / | \ \ \ \

You will see that yours is like like:

/ / / / / | \ \ \

Everything proceeds from that shift.

I believe what you are doing is aiming to the left slightly, then making the horizontal lines "look" right by adjusting the down angle of the camera.   This will correct the horizontal lines, making them appear parallel, and horizontal, but not the vertical lines.

And again, this all goes unnoticed if you have thicker DoF.   I do a lot of macro work, and some with very very thin DoF ( 0.1 mm ) and managing the focal plane is difficult and tricky.  So this issue is very much exaggerated under these conditions.

 BobORama's gear list:BobORama's gear list
Pentax K-5 Pentax K-1 Sigma 10mm F2.8 EX DC HSM Diagonal Fisheye Pentax smc DA 18-55mm F3.5-5.6 AL WR Samyang 14mm F2.8 IF ED MC Aspherical +9 more
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