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

Started May 18, 2014 | Discussions thread
justin23 Veteran Member • Posts: 4,347
Re: Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Trevor G wrote:

BobORama wrote:

Trevor G wrote:

Perhaps I have no idea what you are getting at, in which case I apologise in advance. Post the full image so we can get some context.

Oops - here it is (I'm so used to posting this image in the past I tend to think everyone knows it):

If you want a real test, shoot a completely flat surface perfectly perpendicular to the normal. Or better, shoot a star field wide open. Focus the center of the image perfectly. You will see various aberations, but they should be equal in magnitude as you get farther from the center. Any decentering will be apparent.

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.

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Trevor G
Silkypix tutorials at:

In the train station shot, I'm struggling to see what is actually in focus. I just don't see it as a good representation myself.

In the mixer photo, I struggled, however i downloaded the photo, and drew some lines across the frame. Yes the right side is ever so slightly less sharp than the left however I really had to look for it. Its not that obvious in this photo. I'd also argue that potentially the right side with such a narrow DOF that the right side may not be the same distance from the camera as the left.

I think there is a combination of you knowing its there, so you'll see it a lot more than anyone else. I'm not convinced its that bad myself.

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