Image quality differences: Zenzanon 40mm PS vs Distagon 40mm?

Hi,<br>

I have searhed sample images that shows if there are significant perfomance difference between Zenzanon PS 40mm

and Hasselblad's 40mm lens. So far I have found none.

<br>

So I am asking if someone could post crop of scanned film, picture taken either with bronica or hasselblad. The

scanning quality doesn't have to be very high, 1600dpi is really enough for rough judgements.

<br>

<br>

Why all this? Because I have owned two pieces of Zenzanon PS 40mm, and I am not really satisfied with the edge

sharpness. So I would like to see if both lenses I have owned are just bad, or are the lack of quality normal for

Zenzanon PS 40mm. And ofcourse, I would like to see how other wide lenses performs.

<br>

<br>Here are <a href="http://usagi.kapsi.fi/ps40/">some examples taken with Zenzanon PS 40mm</a>, however all

text is written in Finnish. But images will tell all necessary..

<br>Straight links to <a href="http://usagi.kapsi.fi/ps40/ps40-test1-small.jpg">one picture</a> and <a

href="http://usagi.kapsi.fi/ps40/ps40-test1-detail.jpg">cropped portion</a>.<br><br>

Sincerelly, Jukka

Terve Usagi!

Itse olen taistellut samojen ongelmien kanssa, mutta oletko tarkistanut, että skannerissa filmin pinta on tasainen tai suurennuskoneessa, jos nämä ovat printistä skannatut.

Itse olen vertaillut tarkkuustaulukkoja rolleiflexin eri linssien ja hasselbladin reunoilta.

hasselblad on juuri siitä vahva, että sen reunapiirto on ainutlaatuista, vaikka verrataan mamiya 7 tai mamiya 6 linsseihin. Monet piirtävät keskeltä paremmin kuin blad, mutta kun mennään reunoille, niin sääntöjään hasselblad on 1.

Joten varmaan hasselin 40 millinen ei petä tässäkään suhteessa.

T Jukka

I have worked a bit with the Hasselblad 40 mm, and I have not seen a distortion and unsharpness like that before. Rather extreme.

The Hasselblad 40 mm have som distortion, but no unsharpness to talk about.

It would be even better with a biogon lens, found in Hasselblad and Mamiya also.

Kind regards Claus

I don't have any film scans for the Hasselblad CF40/4 FLE, but here is a digital image taken recently. The whole scene is shown with a 100% cropped portion as outlined.<div></div>

When I had the ps 40, I thought it was very sharp at at 3 meters, but with problems at infinity.

<p>Small update. I got nice example of edge sharpness of PS 40 in email.</p>

<p>After that I checked some of my photos and noticed that the blurry corners occures only at certain situations.<br /> I found many negatives where there is no remarkable blurryness at corners, even foreground of the image fills the corners of the negative.</p>

<p>Form the negative taken at f/16 I can enlarge 15"x15" print which has no problem with corners!</p>

<p>That makes me wonder why I have such problems often when there are distant objects near the corners? Even when I have focused lens to the infinity. That sounds quite similar with problems that <strong>Erlend Sæteren</strong> mentioned above.</p>

<p>ps. I will post examples of good corner sharpness soon.</p>

<p>One thing came to my mind. <strong><em>The image circle is smallest when lens is focused to infinity</em> </strong> (and largest when focused to near). That could explain everything because at the edges of the image circle the image quality will always suffer.<br>

There are still old page about the lens <a href="http://www.tamron.com/bronica/prod/sq40.asp">http://www.tamron.com/bronica/prod/sq40.asp</a> but there are only MTF curves, no any data about image circle.<br>

Have to check if I can mount lens somehow to my view camera and then roughly measure the size of image circle!</p>

<p>I wonder... could the problem observed be due to negative curved at the moment of the scan? Probably this could be checked by looking at the presence of grain in the scan: regardless of the blurriness of the lens, the grain should be sharp.</p>

<p>Hi,</p>

<p>The blurriness is in the film. It's visible in the negative/positive and also prints made in wet dark room using negative carrier with glass both side.</p>

<p>The Bronica was used by lot of photographers during film era, so if this is common problem, then somewhere should be references to it.</p>

<p>But I haven't seen any.</p>

<p>Some things that I haven't (still) investigated:</p>

<ul>

<li>Could some film back allow too much curvature for film (usually wide field lenses suffer most from that)? This could explain why only some pictures have blurry corners.</li>

<li>Is it only my Bronica SQ-Ai body? Would any other body also give same result?</li>

<li>The size of image circle... How does focusing distance and/or used aperture affect to it?</li>

</ul>

<p> </p>

Jukka<br><br>I don't have a Zenzanon 40 mm. But generally, it could be flim flatness, yes. Yet, if film would not lay flat in the gate, the 'bulge' would probably be a straight line across the frame, or if not (and much less likely) a 'bulge' in the middle of the frame. Bulging corners, i.e. film in a corner, where it is held in position on two sides, bulging up would be extremely unlikely. So either a line across the frame, or the center of the frame should be slightly blurry if it was film flatness.<br><br>Wide angle lenses typically have trouble keeping up performance going out from the image center. And my bet is that it's that what you are seeing.