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09-15-2007, 10:44 PM   #1
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Possible Front Focusing Issues...Help?

About two weeks ago I became part of the Pentax family. I bought myself a K10D and the FA 50 1.4. I love the camera and 'most' of the photos that it gives me. I say most because I am having trouble with pictures which are shot wide open or close to it. I have uploaded two pictures on my Flickr at Flickr: Photos from TFTM. I have a feeling its a front focussing issue but perhaps you guys could give me a more solid answer.

-Rajiv

09-16-2007, 12:20 AM   #2
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Are you certain it's not just motion blur/camera shake? It could be front focus...but since those examples don't show where the actual focus lies (no foreground objects or horizontal planes) it might be perfectly focused but just shaken a bit too much. Just something to check.
09-16-2007, 12:58 AM   #3
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Shutter speed at 1/15 and 1/10 sec

Both photos are at very slow shutter speeds. And like previous poster says, the shots may be blur due to movement. It is better to have more testshots especially in day light testing. For testing front focusing, many links suggest use of tripod if you happen to have one.

I ran into a lot of soft pictures due to narrow DOF, kids' movement and slow shutter speed in poor lighting. After 10 days of testing, I returned my 1st copy of FA 50 f/1.4 for an exchange. Not that I am encouraging you to exchange, with the amateur experience in me, it is very difficult for me to tell if a lens has a problem as most problems can actually come from my inexperience. I tested my 1st copy for indoor with sufficient lightings, outdoor with good lightings and indoor with poor lightings forcing aperture to go to f/2.0, f/1.8 .. f/1.4 for various testings.

There are places for testing front focusing, search in google and I will bring back some links tomorrow. As for my own 'put on the lens and test as normal usage', you can reference my tests in these blog posts:

Indoor with sufficient lighting:
Pentax SMC FA 50 f/1.4 Test Shots - Hin's Tech Corner

Outdoor (also try to use Av mode and turn aperture to wider aperture such as f/2.8, f/2.0, f/1.8 etc. for testing sharpness)
Love is Kind - Hin's Photo Blog

Indoor with poor lighting
Happy Birthday to Sweetie Ben - Hin's Photo Blog

And picture link goes to my Flickr account with 'all sizes' and exifs in 'more properties'

Pictures from my 2nd copy (seems better sharpness than 1st copy)
Pentax FA 50 f/1.4 2nd copy - a photoset on Flickr



FA 50 f/1.4 (test3) - a photoset on Flickr

f/2.0


f/2.0, 1/100sec, iso 800 (should have tried iso 400)



Thanks,
Hin

Last edited by hinman; 09-17-2007 at 10:57 AM.
09-16-2007, 04:48 AM   #4
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I had considered that possibility that the slow shutter speeds might have contributed to the problem. I am going to a butterfly conservatory today, I will shoot some more and try to keep the shutter speeds up.

09-16-2007, 07:37 AM   #5
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a link on nikon 70 testchart (with front focusing test)

Here is one link that I make reference to

Nikon D70 Focus Chart

but I have not had the time to digest all the information. Inside, you see reference to front focusing test and the chart to use with front focusing test best to do with a tripod setting the camera in a 45 degree angle with the chart.

All the best. And I will update with more when I find them appropriate for front focusing casual testing. The above link may be too much and a bit off topic from Pentax. But I find it a good read for reference and get informed from other's valuable experience.

Hin
09-16-2007, 08:40 AM   #6
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I don't think you have a focus problem. Look at hinman's dog picture. The focal point is on the nose, crisp and clear, from there everything starts getting softer. This is natural with larger apertures with this lens. I see a similar pattern with your pictures but shake appears to have created a blurred effect.
09-16-2007, 02:51 PM   #7
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QuoteOriginally posted by Ahab Quote
I don't think you have a focus problem. Look at hinman's dog picture. The focal point is on the nose, crisp and clear, from there everything starts getting softer. This is natural with larger apertures with this lens. I see a similar pattern with your pictures but shake appears to have created a blurred effect.
I see your point. That's why I waited on my results today to be sure. Today I went and shot butterflies at a conservatory where it would unambiguous whether the focus was off. Unfortunately for me I forgot my memory card so I have no evidence. However what I can say is, I kept the shutter speed between 1/350 to 1/1000 sometimes even higher. I used aperture from 1.7 to 2.8. After each shot I examined the area of the picture which the camera said was in focus. This is most cases was the particular butterfly I was shooting. More often than not, it was totally out of focus. If I received results similar to the dog picture I could understand it being my error but I didn't see evidence of this. I will take some more and post them up.

That being said, suppose for a second the lens has a fault. Would I take the lens back to where I bought it (B&H) or send it into Pentax for warranty? Keep in mind I've had lens for roughly 2 weeks but I am nowhere close to B&H.
09-17-2007, 10:00 AM   #8
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I'd call B&H and see what they say. You obviously have done your part to prove a defect exists.

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