Do I need a new lens

deltoidjohn · 01-05-2011, 09:43 PM

The Sigma 28-80 is not a terribly sharp lens (I've got one myself which came with an old SLR kit I purchased for some other included lenses), but stopping down to f8 should help it perform it's best.

What you may be seeing though, is lack of contrast. Contrast can have a big effect on percieved sharpness, and in the three photos you've posted above, the one you percieve to be sharpest is also the one with the most contrast. I've found the 28-80 to have very little contrast and an almost milky haze at times. Try increasing the contrast in photoshop and see what effect that has.

One other piece of advice I would offer is to turn on Centre-point AF & AF-S (auto focus single) which are both located in the second page of the manual. Then focus by placing the key focal point ( subjects face/eyes) inside the centre circle of the K-X's viewfinder. Once AF locks on, reframe your shot. Doing it any other way (particularly with the K-X which does not give you a red dot to confirm the selected focus point as manu other cameras do) can result in another part of the photo becoming the primary focal point (eg hands or chest), and this can result in the face falling outside of the depth of field.

trishytee · 01-06-2011, 12:05 AM

Love to Tommot, er what is EXIF. does it stand for exact information? And I shall do the test. Meanwhile what are your thoughts on my tamron/DA question?

**Ash** · 01-06-2011, 12:18 AM

Originally posted by trishytee

I have noticed on auto a hell of a lot of whirring seems to occur?Oh, and I do shoot in raw. Sorry Ash I was being funny when I talked about IQ above I was playing with words. (Sharp? Stupid?) Keep it coming. Let me know thoughts on Tamron 28-75 Ooops jsut remembered the ad said for a: Tamron AF 28-75mm F/2.8 XR Di LD Aspherical (IF) Macro Lens with NIKON mount. Is that only for Nikon or will it go on a pentax. Yes, my IQ is not to high either.

Whirring just means the camera's frantically trying to find focus - don't worry about this.
Forget the Nikon mount version - you need a Pentax K-mount version.
But the 28-75 is a great go-to close-shot wedding lens - I'm sure you'll find it considerably sharper, and provide better depth of field control, than your current Sigma.

Tommot1965 · 01-06-2011, 01:20 AM

Originally posted by trishytee

Love to Tommot, er what is EXIF. does it stand for exact information? And I shall do the test. Meanwhile what are your thoughts on my tamron/DA question?

Exchangeable image file format = EXIF.

basicly all the information that the camera was set at when the image was taken.

Focal length, F stop, Shutter speed, ISO are the big four ..others are the metering pattern used, etc etc etc

Exchangeable image file format - Wikipedia, the free encyclopedia

that lens is a nikon mount..and wont fit.

get a Tamron 28-75 by all means...but for pentax.

what pentax lens was you thinking of?

trishytee · 01-06-2011, 02:54 AM

Thanks for your comments Ash, you are alleviating my concerns.
tommott: focal lengh 28mm f8 1/320 ISO200 (lowest option)Metering mode, pattern.
and it was the one suggested by Ash DA17-70

Tommot1965 · 01-06-2011, 03:03 AM

Originally posted by trishytee

Thanks for your comments Ash, you are alleviating my concerns.
tommott: focal lengh 28mm f8 1/320 ISO200 (lowest option)Metering mode, pattern.
and it was the one suggested by Ash DA17-70

can your remember how far you were from the subject?

trishytee · 01-06-2011, 03:44 AM

I would say about three to four metres.

Tommot1965 · 01-06-2011, 04:10 AM

.at 3 metres the DOF is 5.76 metres....

so plenty of room for the subjects at the rear to be in focus...

so its either a soft lens..or bad calibration...and judging what others have said about the lens in question..its probably the former .....so after all this ..Phew indeed...yes , you do need to buy a new lens..

**Rondec** · 01-06-2011, 05:01 AM

I definitely think you need a new lens. As others have said, there may be some issues with the lens - camera body interaction, creating some back focus or front focus issues, but at f8, I would think something in the photo would be in focus and it just really looks generally soft.

The question you have to ask yourself is what focal lengths would be most useful for you. Personally, on a camera like the kx, which is a crop format, I prefer a lens that starts wider than 28mm -- more in the 16 to 18mm range. There are 17-70 options available from both Sigma and Pentax, 16-50 f2.8 from Pentax and 17-50 f2.8 from Tamron. The Tamron is very reasonably priced and an attractive lens, although some people have complained about front focus/back focus issues with it as well.

The other thing to consider would be a prime lens. There are multiple options there, but the thing would be to find the focal length that you think you would use the most in normal shooting, but I would say you need a bread and butter zoom that is sharp first.

Haakan · 01-07-2011, 01:25 AM

You might also want to consider a little sharpening of your images in the post processing. Since you shoot RAW, you often need to add a little sharpening to compensate for the AA filter that is found in digital cameras.

I did a little adjustment of your first image, and it seems to take to sharpening quite nicely (of course there are some artifacts when doing the sharpening on the compressed image posted here in the forum, so you should try it on your original and see if it helps).

I uploaded an image where I put the one I sharpened side by side to your original.
If you do not want me to post a processed version of your image, please tell me and I will remove it directly.

Best regards,
Haakan

Tommot1965 · 01-07-2011, 02:34 AM

Haakan

thats looks loads better..nice job..

trishytee · 01-07-2011, 02:40 AM

I don't have a problem with you playing. I did that, just hit 'sharpen more" once. BUT, when I enlarge
to what would be an 8x12 the artifacts really do show. Interestingly I have just found a pic with same settings taken with this lens on the 1stD and I think it is time for a new lens as it doesn't seem to like the KX (sorry about subject, one of my daughter's exes)

Haakan · 01-07-2011, 07:15 AM

For me, "sharpen more" is often too agressive and give me little control. I like "smart sharpen" better, using correction of gaussian blur or lens blur. I usually start with 1 px and amount of 100% and play both these parameter up and down while viewing the image att 100% or 200% to see that I do not get too much artifacts.

Another option which I have had good success is to use FocusMagic. It can be downloaded for trial purposes if you like to try it.

As for the 1stD, since that was a 6 MPix camera it was not as revealing as your new camera, more mega pixels do put more demand on the lens. Still, I think that it is worth playing around with sharpening somewhat to see if there is something to gain there.

Best regards,
Håkan

trishytee · 01-07-2011, 09:13 AM

Thanks so much Hakan; I shall certainly do as you suggest. this will certainly improve on the close ups, but think I might just have to take the plunge with the new lens in order to get all in focus. As tommotte said at f8 ect my people in back should have been well in the DOF (sob sob). I have noted your recipe for sharpening and shall apply. I just don't seem to have these probs with close up work?????See attached. Yes overall she has been softened with GB but her eyes show you how sharp I can get up close. I give up!!!

Frogfish · 01-07-2011, 10:04 AM

Hi Trishy. Same as previously - a little judicious sharpening (I used a sharpening brush in Aperture 3) will do it. Just sharpen the areas you want to .... such as her eyes and mouth. It worked it treat when I tried it just now.

Do note however that the highlights are blown in this shot - dial back the exposure or brush over the blanket with a Burn brush to bring back some texture. Usually portraits such as this are NOT at their best when too sharp - such portraits should have a nice soft look and your shot isn't far off with a little TLC !

01-07-2011, 01:25 AM	#25
Haakan Senior Member Join Date: Jun 2008 Location: Stockholm Photos: Gallery Posts: 182	You might also want to consider a little sharpening of your images in the post processing. Since you shoot RAW, you often need to add a little sharpening to compensate for the AA filter that is found in digital cameras. I did a little adjustment of your first image, and it seems to take to sharpening quite nicely (of course there are some artifacts when doing the sharpening on the compressed image posted here in the forum, so you should try it on your original and see if it helps). I uploaded an image where I put the one I sharpened side by side to your original. If you do not want me to post a processed version of your image, please tell me and I will remove it directly. Best regards, Haakan Attached Images

01-07-2011, 02:40 AM	#27
trishytee Senior Member Join Date: Jan 2009 Location: Mandurah Perth Photos: Gallery \| Albums Posts: 221 Original Poster	I don't have a problem with you playing. I did that, just hit 'sharpen more" once. BUT, when I enlarge to what would be an 8x12 the artifacts really do show. Interestingly I have just found a pic with same settings taken with this lens on the 1stD and I think it is time for a new lens as it doesn't seem to like the KX (sorry about subject, one of my daughter's exes) Attached Images

01-07-2011, 09:13 AM	#29
trishytee Senior Member Join Date: Jan 2009 Location: Mandurah Perth Photos: Gallery \| Albums Posts: 221 Original Poster	Thanks so much Hakan; I shall certainly do as you suggest. this will certainly improve on the close ups, but think I might just have to take the plunge with the new lens in order to get all in focus. As tommotte said at f8 ect my people in back should have been well in the DOF (sob sob). I have noted your recipe for sharpening and shall apply. I just don't seem to have these probs with close up work?????See attached. Yes overall she has been softened with GB but her eyes show you how sharp I can get up close. I give up!!! Attached Images

01-05-2011, 09:43 PM	#16
deltoidjohn Forum Member Join Date: May 2010 Location: Gold Coast, QLD Posts: 88	The Sigma 28-80 is not a terribly sharp lens (I've got one myself which came with an old SLR kit I purchased for some other included lenses), but stopping down to f8 should help it perform it's best. What you may be seeing though, is lack of contrast. Contrast can have a big effect on percieved sharpness, and in the three photos you've posted above, the one you percieve to be sharpest is also the one with the most contrast. I've found the 28-80 to have very little contrast and an almost milky haze at times. Try increasing the contrast in photoshop and see what effect that has. One other piece of advice I would offer is to turn on Centre-point AF & AF-S (auto focus single) which are both located in the second page of the manual. Then focus by placing the key focal point ( subjects face/eyes) inside the centre circle of the K-X's viewfinder. Once AF locks on, reframe your shot. Doing it any other way (particularly with the K-X which does not give you a red dot to confirm the selected focus point as manu other cameras do) can result in another part of the photo becoming the primary focal point (eg hands or chest), and this can result in the face falling outside of the depth of field.

01-06-2011, 12:05 AM	#17
trishytee Senior Member Join Date: Jan 2009 Location: Mandurah Perth Photos: Gallery \| Albums Posts: 221 Original Poster	Love to Tommot, er what is EXIF. does it stand for exact information? And I shall do the test. Meanwhile what are your thoughts on my tamron/DA question?

01-06-2011, 12:18 AM	#18
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Originally posted by trishytee I have noticed on auto a hell of a lot of whirring seems to occur?Oh, and I do shoot in raw. Sorry Ash I was being funny when I talked about IQ above I was playing with words. (Sharp? Stupid?) Keep it coming. Let me know thoughts on Tamron 28-75 Ooops jsut remembered the ad said for a: Tamron AF 28-75mm F/2.8 XR Di LD Aspherical (IF) Macro Lens with NIKON mount. Is that only for Nikon or will it go on a pentax. Yes, my IQ is not to high either. Whirring just means the camera's frantically trying to find focus - don't worry about this. Forget the Nikon mount version - you need a Pentax K-mount version. But the 28-75 is a great go-to close-shot wedding lens - I'm sure you'll find it considerably sharper, and provide better depth of field control, than your current Sigma.

01-06-2011, 01:20 AM	#19
Tommot1965 Veteran Member Join Date: Sep 2010 Location: Perth Western Australia Photos: Gallery \| Albums Posts: 1,026	Originally posted by trishytee Love to Tommot, er what is EXIF. does it stand for exact information? And I shall do the test. Meanwhile what are your thoughts on my tamron/DA question? Exchangeable image file format = EXIF. basicly all the information that the camera was set at when the image was taken. Focal length, F stop, Shutter speed, ISO are the big four ..others are the metering pattern used, etc etc etc Exchangeable image file format - Wikipedia, the free encyclopedia that lens is a nikon mount..and wont fit. get a Tamron 28-75 by all means...but for pentax. what pentax lens was you thinking of?

01-06-2011, 02:54 AM	#20
trishytee Senior Member Join Date: Jan 2009 Location: Mandurah Perth Photos: Gallery \| Albums Posts: 221 Original Poster	Thanks for your comments Ash, you are alleviating my concerns. tommott: focal lengh 28mm f8 1/320 ISO200 (lowest option)Metering mode, pattern. and it was the one suggested by Ash DA17-70

01-06-2011, 03:03 AM	#21
Tommot1965 Veteran Member Join Date: Sep 2010 Location: Perth Western Australia Photos: Gallery \| Albums Posts: 1,026	Originally posted by trishytee Thanks for your comments Ash, you are alleviating my concerns. tommott: focal lengh 28mm f8 1/320 ISO200 (lowest option)Metering mode, pattern. and it was the one suggested by Ash DA17-70 can your remember how far you were from the subject?

01-06-2011, 03:44 AM	#22
trishytee Senior Member Join Date: Jan 2009 Location: Mandurah Perth Photos: Gallery \| Albums Posts: 221 Original Poster	I would say about three to four metres.

01-06-2011, 04:10 AM	#23
Tommot1965 Veteran Member Join Date: Sep 2010 Location: Perth Western Australia Photos: Gallery \| Albums Posts: 1,026	.at 3 metres the DOF is 5.76 metres.... so plenty of room for the subjects at the rear to be in focus... so its either a soft lens..or bad calibration...and judging what others have said about the lens in question..its probably the former .....so after all this ..Phew indeed...yes , you do need to buy a new lens..

01-06-2011, 05:01 AM	#24
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	I definitely think you need a new lens. As others have said, there may be some issues with the lens - camera body interaction, creating some back focus or front focus issues, but at f8, I would think something in the photo would be in focus and it just really looks generally soft. The question you have to ask yourself is what focal lengths would be most useful for you. Personally, on a camera like the kx, which is a crop format, I prefer a lens that starts wider than 28mm -- more in the 16 to 18mm range. There are 17-70 options available from both Sigma and Pentax, 16-50 f2.8 from Pentax and 17-50 f2.8 from Tamron. The Tamron is very reasonably priced and an attractive lens, although some people have complained about front focus/back focus issues with it as well. The other thing to consider would be a prime lens. There are multiple options there, but the thing would be to find the focal length that you think you would use the most in normal shooting, but I would say you need a bread and butter zoom that is sharp first.

01-07-2011, 02:34 AM	#26
Tommot1965 Veteran Member Join Date: Sep 2010 Location: Perth Western Australia Photos: Gallery \| Albums Posts: 1,026	Haakan thats looks loads better..nice job..

01-07-2011, 07:15 AM	#28
Haakan Senior Member Join Date: Jun 2008 Location: Stockholm Photos: Gallery Posts: 182	For me, "sharpen more" is often too agressive and give me little control. I like "smart sharpen" better, using correction of gaussian blur or lens blur. I usually start with 1 px and amount of 100% and play both these parameter up and down while viewing the image att 100% or 200% to see that I do not get too much artifacts. Another option which I have had good success is to use FocusMagic. It can be downloaded for trial purposes if you like to try it. As for the 1stD, since that was a 6 MPix camera it was not as revealing as your new camera, more mega pixels do put more demand on the lens. Still, I think that it is worth playing around with sharpening somewhat to see if there is something to gain there. Best regards, Håkan

01-07-2011, 10:04 AM	#30
Frogfish Veteran Member Join Date: Dec 2009 Location: Shanghai Posts: 4,490	Hi Trishy. Same as previously - a little judicious sharpening (I used a sharpening brush in Aperture 3) will do it. Just sharpen the areas you want to .... such as her eyes and mouth. It worked it treat when I tried it just now. Do note however that the highlights are blown in this shot - dial back the exposure or brush over the blanket with a Burn brush to bring back some texture. Usually portraits such as this are NOT at their best when too sharp - such portraits should have a nice soft look and your shot isn't far off with a little TLC !