Image lack sharpness - Pentax K-x with 18-55mm lens

Ken T · 04-05-2010, 08:59 PM

Krishna, in the picture below, if I didn't tell the camera to use the center focus point to focus on the eye, then it would focus on the leaves in the forground and we wouldn't be able to see the eye .

Last edited by Ken T; 04-05-2010 at 09:09 PM.

kxr4trids · 04-05-2010, 10:21 PM

It's probably worth noting, since you are comparing it to a canon, that the k-x doesn't have the in-viewfinder focus point indicators that the canon does. It doesn't affect the functionality of the camera too much once you adapt to it, (that's why everyone is saying to use center focus) but may be one source of your concerns.

krishna · 04-06-2010, 06:47 AM

Taking your inputs into consideration, took some more snaps to correct my focusing skills and uploaded for review.

**kiwi_jono** · 04-08-2010, 02:22 AM

I was new to DSLR when I got my K-x (although have shot a bit of manual SLR) and I was finding it hard to get consistent focusing results on my subjects until I changed focussing 11 / 5 points to center point only (not multizone). Using a single point, I focus (half shutter press) with the center of viewfinder on region I want in focus then move camera to frame the shot I want and fully press shutter. Known as "Focus and recompose". Does not suit everyone and I'm sure the multipoint has its uses but certainly works well for me.

BTW - love the cats eye shot Ken!

clmonk · 04-08-2010, 07:30 AM

One thing you might want to try in order to determine where your issues lie. Put your camera on a steady tripod. Take off all filters. Point your camera at a brick wall, but at something other than a 90 degree angle to the wall. Place a mark on the wall and spot focus on said mark. If you have a cable release, all the better. Shoot multiple shots at various lens openings. This will let you know if your lens is front-focusing or back focusing. It will also give you a practical exercise in depth of field.

StepOne · 04-08-2010, 08:38 AM

i changed to center focus point since day 1 with my camera. At least for me is what i need in 99% of situations.

Ken that's a beautiful picture

vize · 04-09-2010, 06:55 AM

As others have said center point focus and recompose. Manual focus with live view also works well for me.

paulo0916 · 04-09-2010, 07:31 AM

Hello everyone,

Newbie Kx owner here just last January and after reading a few posts I would just like to ask is if you're saying center focus point are you pertaining to just one subject or can you also do that in a group picture (family gatherings, childrens party, etc...).

Thanks.

Marc Sabatella · 04-09-2010, 01:24 PM

Doesn't matter how many subjects you are dealing with; the camera can only focus at one distance at a time. So in group setting, you aim somewhere between the closest and farthest person, and make sure you have a small aperture so that depth of field (Google it is you're not familiar with the term) will extend far enough in front and behind to get everyone in focus.

gebco · 04-11-2010, 10:32 AM

I thought my kit lens was soft too. However, I have since adjusted the focus on my K-x and, so far at least, it seems sharper.

Edit: I don't think the OP's photos here show focus adjustment needed; they simply look OOF, and, in the case of the snake, overexposed.

jct us101 · 04-11-2010, 02:40 PM

Could you specify this focus issue, because my new Nikon D50 has the same problem, but every Pentax and Canon DSLR I've used can focus on multiple things at once. I'm assuming you mean because of the DOF rules, you can't focus on two different planes at once (since you don't have a tilt shift lens most likely)?

RioRico · 04-11-2010, 06:11 PM

Originally posted by jct us101

Could you specify this focus issue, because my new Nikon D50 has the same problem, but every Pentax and Canon DSLR I've used can focus on multiple things at once. I'm assuming you mean because of the DOF rules, you can't focus on two different planes at once (since you don't have a tilt shift lens most likely)?

A lens cannot be focused at multiple points. Assuming its image field is pretty flat, it can focus on just one point in one plane at a time. With a tilt-shift system, that plane can be at an angle; otherwise it's parallel to the sensor or film. (Curved-field lenses are something else, but you hopefully won't run into many of those now.)

A camera that SEEMS to focus at multiple points, is reading the distance to those points, then applying an algorithm involving those distances and the aperture, to try to get them all within DOF range. Maybe we need a sensor that marks those points, determines a plane they're all in (but no more than 3 of them), and physically orients itself (and the lens) to be parallel to that plane. Don't hold your breath.

jct us101 · 04-11-2010, 06:26 PM

Well for example on my Rebel when I focus on something, sometimes 5 of the 9 AF points will light up red indicating that they've locked focus on different areas of the photo.

lurchlarson · 04-11-2010, 06:30 PM

Make sure you are shooting at at least 1/60 or 100 if you are zoomed all the way in. Also try stopping down a bit.

**rparmar** · 04-11-2010, 06:39 PM

Originally posted by jct us101

Well for example on my Rebel when I focus on something, sometimes 5 of the 9 AF points will light up red indicating that they've locked focus on different areas of the photo.

But read what RioRico posted 15 minutes before you. All those lights in the display are there to give you a good feeling. Despite this, the camera is focusing on only one thing. It's a law of optics.

04-11-2010, 10:32 AM	#25
gebco Veteran Member Join Date: Mar 2010 Location: Winnipeg Photos: Gallery \| Albums Posts: 329	I thought my kit lens was soft too. However, I have since adjusted the focus on my K-x and, so far at least, it seems sharper. Edit: I don't think the OP's photos here show focus adjustment needed; they simply look OOF, and, in the case of the snake, overexposed. Last edited by gebco; 04-11-2010 at 11:03 AM. Reason: Further info

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04-05-2010, 08:59 PM	#16
Ken T Veteran Member Join Date: Mar 2008 Location: California, USA Posts: 536	Krishna, in the picture below, if I didn't tell the camera to use the center focus point to focus on the eye, then it would focus on the leaves in the forground and we wouldn't be able to see the eye . Last edited by Ken T; 04-05-2010 at 09:09 PM.

04-05-2010, 10:21 PM	#17
kxr4trids Senior Member Join Date: Mar 2010 Location: VA Photos: Albums Posts: 227	It's probably worth noting, since you are comparing it to a canon, that the k-x doesn't have the in-viewfinder focus point indicators that the canon does. It doesn't affect the functionality of the camera too much once you adapt to it, (that's why everyone is saying to use center focus) but may be one source of your concerns.

04-06-2010, 06:47 AM	#18
krishna Junior Member Join Date: Apr 2010 Location: CT Photos: Albums Posts: 41 Original Poster	Taking your inputs into consideration, took some more snaps to correct my focusing skills and uploaded for review.

04-08-2010, 02:22 AM	#19
kiwi_jono Loyal Site Supporter Join Date: Dec 2009 Location: Christchurch, New Zealand Photos: Gallery \| Albums Posts: 2,437	I was new to DSLR when I got my K-x (although have shot a bit of manual SLR) and I was finding it hard to get consistent focusing results on my subjects until I changed focussing 11 / 5 points to center point only (not multizone). Using a single point, I focus (half shutter press) with the center of viewfinder on region I want in focus then move camera to frame the shot I want and fully press shutter. Known as "Focus and recompose". Does not suit everyone and I'm sure the multipoint has its uses but certainly works well for me. BTW - love the cats eye shot Ken!

04-08-2010, 07:30 AM	#20
clmonk Senior Member Join Date: May 2009 Location: Eastern TN Posts: 269	One thing you might want to try in order to determine where your issues lie. Put your camera on a steady tripod. Take off all filters. Point your camera at a brick wall, but at something other than a 90 degree angle to the wall. Place a mark on the wall and spot focus on said mark. If you have a cable release, all the better. Shoot multiple shots at various lens openings. This will let you know if your lens is front-focusing or back focusing. It will also give you a practical exercise in depth of field.

04-08-2010, 08:38 AM	#21
StepOne Senior Member Join Date: Mar 2010 Location: Botosani Photos: Gallery \| Albums Posts: 285	i changed to center focus point since day 1 with my camera. At least for me is what i need in 99% of situations. Ken that's a beautiful picture

04-09-2010, 06:55 AM	#22
vize Junior Member Join Date: Feb 2010 Posts: 45	As others have said center point focus and recompose. Manual focus with live view also works well for me.

04-09-2010, 07:31 AM	#23
paulo0916 Inactive Account Join Date: Mar 2010 Location: Manila Posts: 13	Hello everyone, Newbie Kx owner here just last January and after reading a few posts I would just like to ask is if you're saying center focus point are you pertaining to just one subject or can you also do that in a group picture (family gatherings, childrens party, etc...). Thanks.

04-09-2010, 01:24 PM	#24
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Doesn't matter how many subjects you are dealing with; the camera can only focus at one distance at a time. So in group setting, you aim somewhere between the closest and farthest person, and make sure you have a small aperture so that depth of field (Google it is you're not familiar with the term) will extend far enough in front and behind to get everyone in focus.

04-11-2010, 02:40 PM	#26
jct us101 Veteran Member Join Date: Jun 2008 Location: Rohnert Park, CA Posts: 3,793	Could you specify this focus issue, because my new Nikon D50 has the same problem, but every Pentax and Canon DSLR I've used can focus on multiple things at once. I'm assuming you mean because of the DOF rules, you can't focus on two different planes at once (since you don't have a tilt shift lens most likely)?

04-11-2010, 06:11 PM	#27
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Originally posted by jct us101 Could you specify this focus issue, because my new Nikon D50 has the same problem, but every Pentax and Canon DSLR I've used can focus on multiple things at once. I'm assuming you mean because of the DOF rules, you can't focus on two different planes at once (since you don't have a tilt shift lens most likely)? A lens cannot be focused at multiple points. Assuming its image field is pretty flat, it can focus on just one point in one plane at a time. With a tilt-shift system, that plane can be at an angle; otherwise it's parallel to the sensor or film. (Curved-field lenses are something else, but you hopefully won't run into many of those now.) A camera that SEEMS to focus at multiple points, is reading the distance to those points, then applying an algorithm involving those distances and the aperture, to try to get them all within DOF range. Maybe we need a sensor that marks those points, determines a plane they're all in (but no more than 3 of them), and physically orients itself (and the lens) to be parallel to that plane. Don't hold your breath.

04-11-2010, 06:26 PM	#28
jct us101 Veteran Member Join Date: Jun 2008 Location: Rohnert Park, CA Posts: 3,793	Well for example on my Rebel when I focus on something, sometimes 5 of the 9 AF points will light up red indicating that they've locked focus on different areas of the photo.

04-11-2010, 06:30 PM	#29
lurchlarson Veteran Member Join Date: Nov 2008 Location: Oregon, USA Photos: Albums Posts: 681	Make sure you are shooting at at least 1/60 or 100 if you are zoomed all the way in. Also try stopping down a bit.

04-11-2010, 06:39 PM	#30
rparmar Site Supporter Join Date: Jan 2008 Photos: Gallery Posts: 8,819	Originally posted by jct us101 Well for example on my Rebel when I focus on something, sometimes 5 of the 9 AF points will light up red indicating that they've locked focus on different areas of the photo. But read what RioRico posted 15 minutes before you. All those lights in the display are there to give you a good feeling. Despite this, the camera is focusing on only one thing. It's a law of optics.