Please Help ... Did I get a defective lens?

stills999 · 05-04-2011, 10:44 AM

"BTW, I have almost the same little bus at my house. Given to me by my Mother when she was living in Panama."

My wife is from Colombia (I'm Canadian). You can actually still see these traditional buses but they are used now more for tourism ... by chance one evening, I heard a lot of noise to turn around and see one of these buses (Chiva) with many loud and very drunk tourists.

deadwolfbones · 05-04-2011, 10:48 AM

Focusing looks correct to me...

GeneV · 05-04-2011, 10:59 AM

It is hard for me to tell that there is anything wrong in those attachments, but they have violated a few laws by selling that as "new." Usually those kinds of items are sold as "factory refurbished" or the like.

ToGo · 05-04-2011, 11:07 AM

The halogen lights do have tungsten color balance.

I'm sure you would rather be taking photos than testing the camera, but the following is a good test chart to use. Nikon D70 Focus Chart

rawr · 05-04-2011, 03:34 PM

The lens may 'backfocus' on one body but be fine on another. That's the nature of the fine manufacturing tolerances involved. The lens could probably be 100% fine on your body. Test it a bit. If it works fine, no problem.

Related, and perhaps worth a read:
https://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths
and
LensRentals.com - “This Lens Is Soft” and Other Facts

Marc Sabatella · 05-04-2011, 04:30 PM

Focus tests are notoriously difficult to do correctly. You say you focused on "Baked Potato", but you have to realize the focus "points" are in fact not points at all but largish rectangles. The "Sensor Reheat" button would have been well within range of the central AF sensor.

To get an idea of how bug the focus "points" really are, just try to focus on a black dot on a piece of white paper, with the dot in a variety of different positions. If the camera can focus, then the dot was in range of the selected focus sensor.

This is why well-designed focus test charts have nothing else anywhere near the focus target that the camera could possibly focus on.

FruitLooPs · 05-04-2011, 07:50 PM

Here is the chart I used, with instructions for Pentax. One of my Sigma zoom lenses was off by heaps, and really altered my opinion of how sharp it could be once it was focusing spot on.

PENTAX DSLRs: PART-1. Free Autofocus Adjustment charts for front and back focusing problems. Good for Pentax, Canon and Nikon.

Wheatfield, i'm curious as to this field curvature and how it makes these adjustment charts virtually useless - I was pleased that I found and used one, does this curvature factor mean that my focus is still going to be incorrect in particular situations?

**Kerrowdown** · 05-05-2011, 07:15 AM

Originally posted by SOldBear

B&H may be interested in this. Their logo is on the label, right lower corner.

That was well spotted, what "beedy little peepers" you have.

stills999 · 05-05-2011, 07:49 AM

I tested the lens focus against my 77mm. It seems that the front focus on my microwave was due to my camera having front focus in indoor light. (K-R is known for indoor FF issues it seems.)

Below you can see both my lens have FF indoors and are good outdoors. This solves my issue ... thanks!!

Photo #1 - 40MM DA outdoor - NO FF (very slight)
Photo #2 - 40MM DA indoor - FF Issue
Photo #3 - 77MM FA indoor - FF Issue
Photo #4 - 77MM FA outdoor - NO FF

(Not sure why the color balance is off so much indoors ... i did not check the setting at the time.)

**crewl1** · 05-05-2011, 08:31 AM

Good deal then, eh!

stills999 · 05-05-2011, 08:44 AM

Yes, it turns out to be a good deal ... I'm probably going to keep the lens but will surely put negative feedback!!

ToGo · 05-05-2011, 09:39 AM

That test shot is almost the same FF as I got with my DA40 limited indoors using only manual focus and not relying on the green focus confirmation light. Seem like a very common problem. By adjusting the auto focus to -8 or -9 it helps a little when using the lens with auto focus, but a bit of a pain to change back and forth all the time. Here is what my indoor ff looks like.

Pentax KR - DA 40MM Limited @ 2.8

Pentax DL - DA 40MM Limited @ 2.8

Siegfried · 05-05-2011, 09:44 AM

Stills,
Savox AF engine in K-r doesn't feature wavelength sensor and thus AF performance varies significantly if going from one lightsource type to another. This must be taken into account when checking AF performance and consistence of Pentax youngsters.

Good luck,
Zig

stills999 · 05-05-2011, 10:24 AM

Originally posted by ToGo

That test shot is almost the same FF as I got with my DA40 limited indoors using only manual focus and not relying on the green focus confirmation light. Seem like a very common problem. By adjusting the auto focus to -8 or -9 it helps a little when using the lens with auto focus, but a bit of a pain to change back and forth all the time. Here is what my indoor ff looks like.

Pentax KR - DA 40MM Limited @ 2.8

Pentax DL - DA 40MM Limited @ 2.8

Hah ... I have not had time yet to read all the manual yet and did not realize there even was a focus adjustment ... this is great to know!

Marc Sabatella · 05-05-2011, 03:37 PM

Originally posted by Wheatfield

I have yet to see a well designed focus chart, since none of them take field curvature into account.
This renders them universally useless.

I wouldn't go *that* far, but yes, I would expect most focus test charts to show a bit of FF as a result of this, and I usually try to factor that in when evaluating results. You can get a decent idea of the field curvature of your lens by shooting some text and use that to set your expectations when using a chart.

05-05-2011, 07:49 AM	#24
stills999 Junior Member Join Date: Apr 2011 Location: Miami Posts: 46 Original Poster	Tested the lens I tested the lens focus against my 77mm. It seems that the front focus on my microwave was due to my camera having front focus in indoor light. (K-R is known for indoor FF issues it seems.) Below you can see both my lens have FF indoors and are good outdoors. This solves my issue ... thanks!! Photo #1 - 40MM DA outdoor - NO FF (very slight) Photo #2 - 40MM DA indoor - FF Issue Photo #3 - 77MM FA indoor - FF Issue Photo #4 - 77MM FA outdoor - NO FF (Not sure why the color balance is off so much indoors ... i did not check the setting at the time.) Attached Images

05-05-2011, 09:39 AM	#27
ToGo Inactive Account Join Date: Jan 2011 Location: NYC Photos: Albums Posts: 56	That test shot is almost the same FF as I got with my DA40 limited indoors using only manual focus and not relying on the green focus confirmation light. Seem like a very common problem. By adjusting the auto focus to -8 or -9 it helps a little when using the lens with auto focus, but a bit of a pain to change back and forth all the time. Here is what my indoor ff looks like. Pentax KR - DA 40MM Limited @ 2.8 Pentax DL - DA 40MM Limited @ 2.8 Last edited by ToGo; 05-05-2011 at 09:45 AM.

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05-04-2011, 10:44 AM	#16
stills999 Junior Member Join Date: Apr 2011 Location: Miami Posts: 46 Original Poster	"BTW, I have almost the same little bus at my house. Given to me by my Mother when she was living in Panama." My wife is from Colombia (I'm Canadian). You can actually still see these traditional buses but they are used now more for tourism ... by chance one evening, I heard a lot of noise to turn around and see one of these buses (Chiva) with many loud and very drunk tourists.

05-04-2011, 10:48 AM	#17
deadwolfbones Veteran Member Join Date: Sep 2007 Location: La Crescenta, CA Posts: 7,450	Focusing looks correct to me...

05-04-2011, 10:59 AM	#18
GeneV Veteran Member Join Date: Oct 2008 Location: Albuquerque NM Photos: Albums Posts: 9,830	It is hard for me to tell that there is anything wrong in those attachments, but they have violated a few laws by selling that as "new." Usually those kinds of items are sold as "factory refurbished" or the like.

05-04-2011, 11:07 AM	#19
ToGo Inactive Account Join Date: Jan 2011 Location: NYC Photos: Albums Posts: 56	The halogen lights do have tungsten color balance. I'm sure you would rather be taking photos than testing the camera, but the following is a good test chart to use. Nikon D70 Focus Chart

05-04-2011, 03:34 PM	#20
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	The lens may 'backfocus' on one body but be fine on another. That's the nature of the fine manufacturing tolerances involved. The lens could probably be 100% fine on your body. Test it a bit. If it works fine, no problem. Related, and perhaps worth a read: https://www.lensrentals.com/news/2008.12.22/this-lens-is-soft-and-other-myths and LensRentals.com - “This Lens Is Soft” and Other Facts

05-04-2011, 04:30 PM	#21
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Focus tests are notoriously difficult to do correctly. You say you focused on "Baked Potato", but you have to realize the focus "points" are in fact not points at all but largish rectangles. The "Sensor Reheat" button would have been well within range of the central AF sensor. To get an idea of how bug the focus "points" really are, just try to focus on a black dot on a piece of white paper, with the dot in a variety of different positions. If the camera can focus, then the dot was in range of the selected focus sensor. This is why well-designed focus test charts have nothing else anywhere near the focus target that the camera could possibly focus on.

05-04-2011, 07:50 PM	#22
FruitLooPs Veteran Member Join Date: Dec 2007 Location: New Zealand Photos: Gallery \| Albums Posts: 440	Here is the chart I used, with instructions for Pentax. One of my Sigma zoom lenses was off by heaps, and really altered my opinion of how sharp it could be once it was focusing spot on. PENTAX DSLRs: PART-1. Free Autofocus Adjustment charts for front and back focusing problems. Good for Pentax, Canon and Nikon. Wheatfield, i'm curious as to this field curvature and how it makes these adjustment charts virtually useless - I was pleased that I found and used one, does this curvature factor mean that my focus is still going to be incorrect in particular situations?

05-05-2011, 07:15 AM	#23
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,815	Originally posted by SOldBear B&H may be interested in this. Their logo is on the label, right lower corner. That was well spotted, what "beedy little peepers" you have.

05-05-2011, 08:31 AM	#25
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	Good deal then, eh!

05-05-2011, 08:44 AM	#26
stills999 Junior Member Join Date: Apr 2011 Location: Miami Posts: 46 Original Poster	Yes, it turns out to be a good deal ... I'm probably going to keep the lens but will surely put negative feedback!!

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05-05-2011, 09:44 AM	#28
Siegfried Senior Member Join Date: Apr 2010 Location: in a middle of nowhere Photos: Gallery \| Albums Posts: 165	Stills, Savox AF engine in K-r doesn't feature wavelength sensor and thus AF performance varies significantly if going from one lightsource type to another. This must be taken into account when checking AF performance and consistence of Pentax youngsters. Good luck, Zig

05-05-2011, 10:24 AM	#29
stills999 Junior Member Join Date: Apr 2011 Location: Miami Posts: 46 Original Poster	Originally posted by ToGo That test shot is almost the same FF as I got with my DA40 limited indoors using only manual focus and not relying on the green focus confirmation light. Seem like a very common problem. By adjusting the auto focus to -8 or -9 it helps a little when using the lens with auto focus, but a bit of a pain to change back and forth all the time. Here is what my indoor ff looks like. Pentax KR - DA 40MM Limited @ 2.8 Pentax DL - DA 40MM Limited @ 2.8 Hah ... I have not had time yet to read all the manual yet and did not realize there even was a focus adjustment ... this is great to know!

05-05-2011, 03:37 PM	#30
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by Wheatfield I have yet to see a well designed focus chart, since none of them take field curvature into account. This renders them universally useless. I wouldn't go that far, but yes, I would expect most focus test charts to show a bit of FF as a result of this, and I usually try to factor that in when evaluating results. You can get a decent idea of the field curvature of your lens by shooting some text and use that to set your expectations when using a chart.