Pentax 55-300 problem (I think)

I have just purchased the pentax 55-300 from SRS and am not sure if it is backfocussing and whether it is producing "soft" images.
How can i best test these issues?
Roy

You could start by using a focussing test chart ( http://focustestchart.com/focus21.pdf ) or ( http://regex.info/blog/photo-tech/focus-chart/ ) or ( http://pentaxdslrs.com/newchart.pdf ).

I haven't used it yet but my preference is for the last one as there is only one line of high contrast for the lens to focus on. The others could be wrong as much as the thickness of their centre line.

A tip: Rather than lay the chart flat, and set the camera/lens at 45 degrees. Set the chart to 45 degrees and the camera/lens horizontal. Much easier.

To test for back/forward focusing, the pictures of the test chart should be with the lens wide open, to make the depth of field as narrow as possible. Then you will clearly see where the actual focus point is.

Thanks both will have to print it off at work on Monday.My printer is very poorly

Is this a common problem with the 55-300mm lens? I ask because I was seriously thinking of ordering one from SRS in the next few days. It gets good reviews on other fora (forums??). I am now having second thoughts. I had persuaded myself aginst being lazy see link even though the 18-250mm also gets good reviews, the £100 difference in price swung me toward the 55-300mm.

Ah well.

Howard

Hi Howard
I have since tried a few shots with 3 AA batteries spaced an inch apart and focussed at 300mm with the widest aperture and it always focussed where it was supposed to...perhaps it's me.

Roy

will post some photo's tomorrow.

[quote:3496ace15f="royd63uk"]...perhaps it's me.

Roy

Human error is responsible for most reported problems, so you are not alone.

G

Mine 55-300 has front focus problem (on K10D), -50um in debug mode helped me.

I have now done the chart test,if someone could take a look at them for me who knows what they are interpreting I would be grateful.Also you will notice a couple of them are blurred....tripod movement or what?
Roy

here
link

Not a lot wrong with that lens/camera combination. The centre line of the chart could/should have been closer to horizontal.

The idea is that the numbers above and below the centre line should fade out of focus at the same rate in both directions with the centre line in sharp focus. It seems they do, so I'd say your hardware is in order. If you are not hitting focus, it's your technique you need to work on.

The blurry ones . . . something moved the tripod/camera/lens or the chart moved.

Thanks
I did have a feeling it might be me
must keep taking the tablets
Thanks for your help

This result is really great news. The best you could have hoped for.

The conclusion: any focus issue you have with that camera/lens combo is entirely your fault.

Congratulations - this means that for better photographs, you don't have to rely on crappy service departments, moronic fob-off call-centre 'operatives', money for extra kit, or anything at all...

... except yourself, and practice.

As I say, the best result possible.

It seems as if I can now order with confidence. Any problems that may occur will be entirely down to my clumsiness and lack of expertise.

That will be good to know.


Howard

I've been really pleased with mine on the K10D.

There are some K20D pictures of a rugby match over at PentaxForums.com taken with one, too, that aren't at all bad.

For the price, I think it's a real winner.