Nature need help - sharpness

citrus sky · 01-09-2011, 12:49 PM

I rented a 77mm f1.8 to see if I want to purchase. I wanted to test the speed so went to a duck pond. Could be light as was taken in the afternoon however thought i may be able to get faster shutter speed for sharpness of moving objects at 1.8. any suggestions?
attached two examples taken at same settings.

Attached Images

grainbelt · 01-09-2011, 01:01 PM

The issue with these pics isn't subject movement, it is missed focus and razor thin depth of field.

Both shots appear to have focused behind the bird - the first duck's body feathers are in better focus than the head, and in the second, the rock behind the bird is sharper than the bird.

At the specified settings you would have been better able to get each bird in focus at 1/500 and F/3.5 (two stops slower shutter, two stops smaller aperture).

Still have the issue of missed focus. Were you using the center focus point?

citrus sky · 01-09-2011, 01:09 PM

Thanks for the feedback. I was using center focus point. automatic focus. i'm going back out today to continue to play around so can try manually focusing and see if I can get that. today's weather is about the same so light should be comparable. would you consider changing ISO?

timh · 01-09-2011, 01:12 PM

Your AF might be slightly off with that lens - you could do a quick rough test by shooting along a ruler or tape measure and then zooming into the photo to see if the sharpness is where you aimed the focus point or not. You can dial in some adjustment with the K10, I think.

citrus sky · 01-09-2011, 01:19 PM

This one was taken 1/750 f3.5. same issue with focus. body is good; head is out of focus. I'll try the ruler test. thank you for your suggestions. I'll test same shots with another lens today as well.

grainbelt · 01-09-2011, 01:29 PM

Regarding your ISO question, my K200D has the same sensor, and does fine up to ISO 400.

That would give you the ability to stop down a bit more for more depth of field, but doesn't fix the backfocus issue. Probably best to sort that out, regardless.

Sparkle · 01-09-2011, 06:07 PM

That lens is normally very sharp. The following site may help:

Aperture, shutter and ISO value | SLR Camera Simulator:

Aperture, shutter and ISO value | SLR Camera Simulator

Try it at ISO 1600; Ev 1/150s ad aperture as high an f as possible; average metering.
Then also bracket a few shots.

Kailash · 01-26-2011, 05:25 PM

You may have already tried this but when using centre point focus start by focusing on the area you want to be the sharp like the head or eye then while keeping the shutter release half depressed, so it doesn’t refocus when you take the picture, recompose the image then take you picture. Personally i'm more of a fan of manual focus when it comes to wildlife that’s not moving.
i would also use a higher iso, say 200 or 400 to allow you a higher aperture setting and a greater depth of focus but wouldn't push it much further as anything above iso 800 on the k10 is a bit too noisy for my taste.
Good luck with the lens

**Ash** · 01-28-2011, 01:56 PM

I would suggest not taking your K10D to ISO anything above 800 to avoid loss of detail and increased noise, but focusing issues aside, find scenes that will enable better rendering of your subjects to make your mind up as to whether the 77 ltd is the lens for you, and understand that as it is a prime lens, you will need to zoom with your feet, which if it is not sufficient to get the framing you're after for your subjects, then you may need a longer or zoom telephoto lens.

shootreadyaim · 01-28-2011, 10:06 PM

also i would suggest manual focus at f1.8 you should have a bright viewfinder image so it should not be difficult.

Hamilton · 01-29-2011, 07:15 AM

Good advice...I've been going through this with my new K100d. Will try some of these techniques.

JeffJS · 01-29-2011, 09:53 AM

It's also worth noting for the DOF answers that DOF is a function of both the lens aperture and subject distance. That is, regardless of what your aperture is set at, the further away you are from your subject, the greater the range of your DOF will be.

I'm not seeing any FF or BF in the original shots (maybe that's just me), but simply missed focus. It has been argued here at times that our cameras AF systems (and the focus screens) are calibrated for f2.8 or slower lenses. I also know from owning 3 of them, that the K10d (especially the earlier ones) are notorious for missing focus with these lenses. That is the primary reason for all the K10d hacking to adjust the auto focus.

A few suggestions if you want to manual focus with these lenses. Use the DOF preview (optical preview) to stop your lens down to f2.8 or slower while you are manual focusing. Put a split prism focusing screen in your camera. Use a Magnifying type eye piece. All will aid you in the fun that is manual focusing. These all work for me. Everyone elses mileage may vary. WRT auto-focus, the only thing you can do is hack it and adjust it (pentax-hack.com) or send it in with your lenses (up to 4 of them I think) for a calibration.

citrus sky · 02-02-2011, 02:03 AM

I was more successful the second day out and tried a few of the tests you recommended. these I took at 800ISO. The duck is sharp and am happy with it (was moving slowly); the swan was continuously moving its head up and down and AF couldn't focus quick enough with this lens (DA 50-135) so I had to focus at the bottom of the neck/body and when the head came up it was slightly off on another plain so it is not 100% crisp (the swan head).
MF I don't think I could change quick enough either; any other tricks/tips for focusing on a moving subject that may change distance to the lens slightly each time.

Gareth · 02-02-2011, 03:30 AM

well its not the shutter speeds as they are nice and fast!

f1.8 - the depth of field is soooo shallow that the slightest movement could render an image out of focus so if the subject is moving then its going to be hard to nail it.
I have a Samsung GX10 which is the same as the K10d but in drag and unlike the K20 I have, it doesn't have AF adjustment. The Pentax-F 50mm I have on the K10d back focused terribly and unless I wanted to go into debug mode it was useless under f5.6
On the K20d I can amend this and the lens is transformed and now sharp wide open. Only mentioning as if you camera is back or front focusing then wide open its never going to be sharp. If I was you I would do what someone suggested and photograph a tape measure wide open and then zoom to see where it focused, that'll soon tell you if the camera is spot on or in need of a tweak but be warning that unlike the K20 where you can store different lens in the memory for AF adjustment you can't on the K10d so any adjustments you make effect ALL lenses !

Hamilton · 02-02-2011, 02:06 PM

Those are getting better!

I've been paying close attention to front/back focusing and adjusting it when I can.
I think I'm getting better results.
Here is one I just took. Low light 28mm f2.8 set 4 ISO 800.

01-09-2011, 12:49 PM	#1
citrus sky Inactive Account Join Date: Jan 2011 Location: B.C. Photos: Gallery Posts: 28	need help - sharpness Lens: 77mm f1.8 Camera: K10D Photo Location: duck pond vancouver ISO: 100 Shutter Speed: 1/2000s Aperture: F1.8 I rented a 77mm f1.8 to see if I want to purchase. I wanted to test the speed so went to a duck pond. Could be light as was taken in the afternoon however thought i may be able to get faster shutter speed for sharpness of moving objects at 1.8. any suggestions? attached two examples taken at same settings. Attached Images

01-09-2011, 01:19 PM	#5
citrus sky Inactive Account Join Date: Jan 2011 Location: B.C. Photos: Gallery Posts: 28 Original Poster	This one was taken 1/750 f3.5. same issue with focus. body is good; head is out of focus. I'll try the ruler test. thank you for your suggestions. I'll test same shots with another lens today as well. Attached Images

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01-09-2011, 01:01 PM	#2
grainbelt Veteran Member Join Date: Nov 2008 Location: Minneapolis Photos: Albums Posts: 587	The issue with these pics isn't subject movement, it is missed focus and razor thin depth of field. Both shots appear to have focused behind the bird - the first duck's body feathers are in better focus than the head, and in the second, the rock behind the bird is sharper than the bird. At the specified settings you would have been better able to get each bird in focus at 1/500 and F/3.5 (two stops slower shutter, two stops smaller aperture). Still have the issue of missed focus. Were you using the center focus point?

01-09-2011, 01:09 PM	#3
citrus sky Inactive Account Join Date: Jan 2011 Location: B.C. Photos: Gallery Posts: 28 Original Poster	Thanks for the feedback. I was using center focus point. automatic focus. i'm going back out today to continue to play around so can try manually focusing and see if I can get that. today's weather is about the same so light should be comparable. would you consider changing ISO?

01-09-2011, 01:12 PM	#4
timh Veteran Member Join Date: May 2010 Location: Wales Photos: Gallery \| Albums Posts: 445	Your AF might be slightly off with that lens - you could do a quick rough test by shooting along a ruler or tape measure and then zooming into the photo to see if the sharpness is where you aimed the focus point or not. You can dial in some adjustment with the K10, I think.

01-09-2011, 01:29 PM	#6
grainbelt Veteran Member Join Date: Nov 2008 Location: Minneapolis Photos: Albums Posts: 587	Regarding your ISO question, my K200D has the same sensor, and does fine up to ISO 400. That would give you the ability to stop down a bit more for more depth of field, but doesn't fix the backfocus issue. Probably best to sort that out, regardless.

01-09-2011, 06:07 PM	#7
Sparkle Inactive Account Join Date: Mar 2009 Location: Halifax, Nova Scotia Photos: Gallery \| Albums Posts: 1,521	That lens is normally very sharp. The following site may help: Aperture, shutter and ISO value \| SLR Camera Simulator: Aperture, shutter and ISO value \| SLR Camera Simulator Try it at ISO 1600; Ev 1/150s ad aperture as high an f as possible; average metering. Then also bracket a few shots.

01-26-2011, 05:25 PM	#8
Kailash New Member Join Date: Dec 2010 Location: Victoria Photos: Gallery \| Albums Posts: 22	You may have already tried this but when using centre point focus start by focusing on the area you want to be the sharp like the head or eye then while keeping the shutter release half depressed, so it doesn’t refocus when you take the picture, recompose the image then take you picture. Personally i'm more of a fan of manual focus when it comes to wildlife that’s not moving. i would also use a higher iso, say 200 or 400 to allow you a higher aperture setting and a greater depth of focus but wouldn't push it much further as anything above iso 800 on the k10 is a bit too noisy for my taste. Good luck with the lens

01-28-2011, 01:56 PM	#9
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	I would suggest not taking your K10D to ISO anything above 800 to avoid loss of detail and increased noise, but focusing issues aside, find scenes that will enable better rendering of your subjects to make your mind up as to whether the 77 ltd is the lens for you, and understand that as it is a prime lens, you will need to zoom with your feet, which if it is not sufficient to get the framing you're after for your subjects, then you may need a longer or zoom telephoto lens.

01-28-2011, 10:06 PM	#10
shootreadyaim Inactive Account Join Date: Dec 2010 Location: pennsylvania Posts: 19	also i would suggest manual focus at f1.8 you should have a bright viewfinder image so it should not be difficult.

01-29-2011, 07:15 AM	#11
Hamilton Forum Member Join Date: Jan 2011 Location: Richmond, VA Photos: Gallery Posts: 55	Good advice...I've been going through this with my new K100d. Will try some of these techniques.

01-29-2011, 09:53 AM	#12
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	It's also worth noting for the DOF answers that DOF is a function of both the lens aperture and subject distance. That is, regardless of what your aperture is set at, the further away you are from your subject, the greater the range of your DOF will be. I'm not seeing any FF or BF in the original shots (maybe that's just me), but simply missed focus. It has been argued here at times that our cameras AF systems (and the focus screens) are calibrated for f2.8 or slower lenses. I also know from owning 3 of them, that the K10d (especially the earlier ones) are notorious for missing focus with these lenses. That is the primary reason for all the K10d hacking to adjust the auto focus. A few suggestions if you want to manual focus with these lenses. Use the DOF preview (optical preview) to stop your lens down to f2.8 or slower while you are manual focusing. Put a split prism focusing screen in your camera. Use a Magnifying type eye piece. All will aid you in the fun that is manual focusing. These all work for me. Everyone elses mileage may vary. WRT auto-focus, the only thing you can do is hack it and adjust it (pentax-hack.com) or send it in with your lenses (up to 4 of them I think) for a calibration.

02-02-2011, 03:30 AM	#14
Gareth Veteran Member Join Date: May 2010 Location: South Wales, UK Posts: 768	well its not the shutter speeds as they are nice and fast! f1.8 - the depth of field is soooo shallow that the slightest movement could render an image out of focus so if the subject is moving then its going to be hard to nail it. I have a Samsung GX10 which is the same as the K10d but in drag and unlike the K20 I have, it doesn't have AF adjustment. The Pentax-F 50mm I have on the K10d back focused terribly and unless I wanted to go into debug mode it was useless under f5.6 On the K20d I can amend this and the lens is transformed and now sharp wide open. Only mentioning as if you camera is back or front focusing then wide open its never going to be sharp. If I was you I would do what someone suggested and photograph a tape measure wide open and then zoom to see where it focused, that'll soon tell you if the camera is spot on or in need of a tweak but be warning that unlike the K20 where you can store different lens in the memory for AF adjustment you can't on the K10d so any adjustments you make effect ALL lenses !

02-02-2011, 02:06 PM	#15
Hamilton Forum Member Join Date: Jan 2011 Location: Richmond, VA Photos: Gallery Posts: 55	Those are getting better! I've been paying close attention to front/back focusing and adjusting it when I can. I think I'm getting better results. Here is one I just took. Low light 28mm f2.8 set 4 ISO 800.