A quick lens check [OT]

Got my FA35 in today and just wanted to double check that the focus looks alright. Apologies for the fact that it is pretty underexposed - I've had focus issues in 'real shots' but can't rule out the fact that this is caused by my own woeful technique

http://i204.photobucket.com/albums/bb159/Carzor_Stelatis/Photography/test_35.jpg

(Warning: It's a full-size JPEG so about 6Mb)

Looks a little front focus to me. But wait and see what it looks like for real before adjusting?

Well that's the thing - I've had focus issues (though not talented enough to identify which direction) in 'real' shots (which I unfortunately can't post - family etc.).

I've repeated the test, this time doing it with both the FA35 and my DFA50 Macro (from the same tripod location)

FA35 at f2:
http://i204.photobucket.com/albums/bb159/Carzor_Stelatis/Photography/IMGP4545.jp...

DFA50 at f2.8:
http://i204.photobucket.com/albums/bb159/Carzor_Stelatis/Photography/IMGP4544.jp...

Now on the DFA50 the middle section is perfectly in focus (and the chart as a whole looks a little back-biased, if anything), whereas on the FA35 it isn't (by my rough guess the 10mm is in sharpest focus)

I wouldn't argue. So use the K20's AF adjustment to get it spot on. That's what I did.

While I agree that there is a difference between the two I think you have to expect tolerance differences between different individual lenses and given that these are at the smallest depth of field I think don't look too bad.

The K20D gives you the ability to adjust the focus point of individual lenses providing you only have one of any particular type. See setting 35, AF Adjustment, in the custom settings menu.

However before you make any adjustment I think you need to spend a little more time with setting up your focus chart. In the 3 images you have shown I don't think it is straight. A good check is to review the shot on the camera, magnified, and while looking at the centre line scroll left & right and make sure the centre line is level. If this is wrong you get different results from either side of the chart which is particularly noticeable on the upper RH 20mm point in your 50mm shot.

I think it is also very important to make sure you have accurately set up the 45 degree angle of the camera.

I believe that it is also important, with the K20D, to use daylight to illuminate the chart as different results may be obtained with other forms of lighting.

Having made any adjustment I think it is also worth testing at more usual distances by, say, sticking a printed page up on a wall.

Hope this helps,

Glyn




Glyn

When using these charts I find it easier to do the following:
1. Place the chart on the wall (so you read it sideways)
2. Put the camera, level on a tripod
3. Angle the camera at 45 degrees to the wall.

Always move the focus ring to an extremity first, the AF and take the shot. Consistency is the name of the game.

In fact, this is similar to the Pentax service manual

Finally, I have found that the chart can be too 'clinical'. I always found a chart adjustment followed by a real life test (and further tweak) is always best (normally using a portrait).

HTH,

Matt

Knew to do all of those (might not be precisely 45 degrees is the only flaw) - the only reason I broke out the test charts was that a few 'real shots' (which, as I say above, I can't post I'm afraid) had focus problems which were just about noticeable without zooming to 100%.

I'll give it another go on Sunday (busy tomorrow) and see whether I can make it (or rather my K20D and it) behave