Backfocus

[nikita_kirilkin]

<p>Hi, gentlemen :)<br>

I've bought hasselblad 503cw with dark (ordinary matte screen without split screen) and A12 back.<br>

I found out recently backfocus on my negs (at f/2.8 and 0.9m focusing distance it's about 2 cm). I took my camera to servise and repairman said that's everything ok and that had been my mistake while focusing, because of dark screen.<br>

But I beleive it's due to the back, because insert and back s/n doesnt match. I cant find any information "how to ajust back" in the internet.<br>

Could you please avise me something :)<br>

Thanks</p>

[jeff.grant]

<p>One of my backs had a non-matching insert. I never noticed any focusing issues with it, so I suspect that the back is not the problem. <br>

I take it that you were using a tripod when you were shooting. I wouldn't like to shoot wide open at that distance, handheld, and hope to get sharp shots. If you are new to Hasselblad, there is a high probability that you are the problem. Most folks take a while to get used to it. I certainly did.</p>

[ulrik]

<p>The plane of the film is not determined by the insert or combination of insert and shell. It is determined by the shell. Look inside the shell and you will find two shiny rails against which the film is pressed by the insert's spring-loaded back plate. The position of these rails can be out of specs. Calibration (by bending !!!) requires experience and the measuring tools of a well-equpped Hasselblad workshop.<br>

Ulrik</p>

[q.g._de_bakker]

<p>Unless you know that an elephant trampled over your back, i'd trust the repair man.<br>

Don't mess with the back.</p>

<p>A camera's body length can be out of spec (could easily happen when a herd of elephants uses it for soccer practice), but the repairman would have spotted that.</p>

<p>A focussing screen can indeed cause focussing errors.<br>

For instance when it is inserted upside down. Or when it is a cheap Chinese copy. Or when someone took it apart (to clean in between perhaps) but did not manage to put it back together properly.<br>

The four points it sits on can be out of whack too, but that's not very likely.</p>

<p>And finally, the mirror should be checked for proper position too. That's something i would ask the repair person about (though he should have, and probably has, checked that before already). </p>

[richard_quindry]

<p>I had a similar problem once and was also told by Hasselblad repair that everything was fine - only later to have a job messed up when using portraits with shallow depth of field were out of focus. <br>

I ran more tests and sent it back - finally Hasselblad this time verified that there was a problem.<br>

The mirror has a foam? padding to absorb shock and that it rests on. It disintegrates with age, causing the mirror to sit in an incorrect position.<br>

This is my best guess for what the problem is.<br>

Take some photos of a ruler running 45 degrees to the camera. Focus on the middle of the ruler with the camera on a tripod - shoot wide open. Study with a loupe to see where the camera is focused to confirm if the focus is off.<br>

Rich Quindry</p>

 

[nikita_kirilkin]

<p><strong>Ulrik Neupert, Jeff Grant,</strong><br>

Thanks for useful information!<br>

 <br>

<strong>Q.G. de Bakker,</strong><br>

But I believe the focusing screen is absolutely all right. Also the repairman checked focusing and said that's ok.<br>

 <br>

<strong>RIchard Quindry,</strong><br>

Thank you!<br>

 I've done some tests using tripod and focusing test table. And as a result i have backfocus :)<br>

 Anyway I'm going to buy acute matte screen with split screen and run test again, to be quite sure that wasn't my mistake.</p>