Hasselblad focus innacuracy -- cause?

[willy_boots]

<p>Hi there,<br>

I've been fiddling around with a Hasselblad 500 cm lately, getting to know it and all that. I noticed a lot of my photos were out of focus. Basically, any portrait shot at 2.8 and maybe 4. At first I thought I wasn't holding steady or my eyes weren't good at gauging focus or something, but it kept happening. So, I shot some tests and what I found, very consistently with every shot (I took a lot of shots to be sure it wasn't my eyes not seeing right) is that the focus lands a little further back than what I intend.<br>

Now, I've tested this with 2 lenses and 2 backs and it always comes out like this, so it must be the body, right? But if it were the body, then shouldn't focus at infinity be off? Shouldn't infinity be at least just a little blurry? Because as far as I can tell it's not. I tried another hasselblad that was clearly not sharp at infinity so I've at least seen the mirror not sitting right problem. What could be causing this?<br>

Another note: The tests I did were with objects and the tape measure up pretty close and they would come out with focus being off by about an inch. But when I photograph something around ten feet away (like a cat I photographed recently) it's out of focus and everything right behind it, like a wall, is just bang on super sharp. Same observed about 6 feet away from a person on a couch. Their face is blurry and then the couch is very well defined.<br>

So can this be fixed? I'm not familiar with hasselblad repairs but I was under the impression that it's the kind of camera that everything can be repaired with. It's just that I spoke recently with a camera technician and he was basically like, 'well, if it's in focus when you put the lens to infinity, it must not be the body.'<br>

If anybody could tell me what they think this problem could be, I'd be very grateful. I'm a little discouraged because of course I don't know what's going on in the camera and the repair guy I've spoken to so far doesn't seem to have any ideas what else could be causing the problem. Thanks.</p>

[tim_ludwig2]

<p>Willy,</p>

<p>I'm not an optical expert by any means, but I have used Blads for over thirty years so I'll risk a couple of observations.</p>

<p>To begin with, have all of your tests been done on a solid tripod? If not, that alone can throw you off by a wide margin in close up focusing and subsequent exposure due to body movements, especially with small f numbers.</p>

<p>Secondly, is the screen an original Hasselblad screen? How the screen is fitted to the body is also crucial to successful focus. It is remotely possible that an aftermarket screen is not properly manufactured and maybe not be optically flat which could produce a focusing variation which would give sharp focus at one distance, but be off at another.</p>

<p>Thirdly, the camera (or the screen) may have impact damage which could have thrown off the alignment and therefore the focus.</p>

<p>Also, have you considered your eyes. It is much easier to focus at infinity than in close up. If your eye focus needs correction, you may be mistaking the appearance of sharpness for an image that is actually not quite in focus on the screen. Consider having your eyes checked as well, especially at middle to short focus ranges. Keep in mind that when the optometrist checks your eyes for mid and short ranges, they use a very bright light on the little card that they have you read.....producing a very deep depth of field in your own eye sight. I had my optometrist turn that light way down so we were identifying my actual focus, not apparent focus. It made a very big difference in where he set my prescription for correction.</p>

<p>I'm sure there are other variables that better informed folks might suggest.</p>

<p>When I've needed recent Hasselblad repairs, I've used the folks at KEH repairs with great success. They are quite eager to help by phone, so you might give them a call for better advice on what body adjustments might be needed and made.</p>

<p> </p>

[willy_boots]

<p>Thanks for the response, Tim. My screen doesn't say hasselblad anywhere. How do I tell if it's genuine? And how do you get it back in?! Having some trouble here, but I'm sure I'll figure it out in a sec..</p>

[tim_ludwig2]

<p>To be honest, Willy. I don't think there is a label on the screens except for two very reputable aftermarket ones, Brightscreen and Intenscreen. </p>

<p>Orientation is not important except to have top and bottom surfaces where they belong. You have two tabs, one on each side of the opening which have to be retracted for the screen to drop in. Once it is in place, just slide the waist level or prism finder into place which automatically pushes the tabs back out and secures the screen in place.</p>

<p>If you don't have a manual, I think you can download one from www.butkus.com for a donation.</p>

[tim_ludwig2]

<p>Come to think of it, are you sure that the screen was in right side up to begin with? That would drastically effect focus at close up ranges but not be as apparent at infinity. The bottom will look more frosted or have a Fresnel lens of concentric rings.</p>

[willy_boots]

<p>Ok! Got it back in!</p>

[leighb]

<p>You mentioned a measuring tape. Where are you measuring from?</p>

<p>The distance marked on the lens is from the subject to the film plane, not to the front of the lens.</p>

<p>The film plane is designated by a small circle and line on the side of the magazine.</p>

<p>- Leigh</p>

 

[willy_boots]

<p>Leigh: sorry to be unclear. I mean that i was photographing along a measuring tape with a marker sitting beside the number on the measuring tape that I was focusing on. I had this little pointer aiming at 35, and instead of 35 being in focus, 36 is nice and sharp instead. I did this test a number of times with multiple lenses and multiple backs.</p>

<p>Thanks for the info about the lens scale refering to the film plane and not the end of the lens, though, that's some good info.</p>

 

[Ed_Ingold]

<p>It's possible that the screen height or mirror has been damaged or misadjusted. That wouldn't matter at infinity, because you rely solely on the focusing stop calibration of the lens. Calibration takes a special fixture and techniques. Consider it a "Mr. Goodwrench" project.</p>

<p>The virtual distance of your eye to the ground glass is about arm's length. If you relax your eye looking through the viewfinder, you will tend to look through the glass rather than at it's surface. This causes substantial focusing error. This effect is worse on Acute-Matte screens than the original 500cm screen, because they are brighter (and more transparent).</p>

<p>The trick is to concentrate on any grid markings or the faint image of the Fresnel lens while focusing. If this proves uncomfortable, get a different diopter for the eyepiece, or get a finder with a focusing eyepiece (like a chimney finder or the newest PM45 prism).</p>

[Aoresteen]

<p>Since you say infinity is ok we can assume that the film mags and flange distance is ok.<br>

If you can find a rear ground glass screen for a SWC you can use that to check the focus at the film plane. Put the the camera on a tripod, focus through the WLF then lock the camera open on B. Look at the image on the ground glass (using a magifier will help). The focus should be the same. If not either the screen or mirror is off.<br>

Send it to a repair shop that can put it on an optical bench and adjust the screen or mirror. David Odess should be able to do this.</p>

[rashed_s]

<p>I had most of my images not into sharp focus, with all, the 50MM, 80MM, 150MM and the 250MM hasslblad lenses, when used by me of course, it is another story when used by a friend of mine, now I have a focusing aid which attach to the finder of the camera and it slips in and out, that did help me with obtaining a better focus, I also do not recommend F4 for portraits, specially out door and when using a manual focusing camera, the DOF at that F stop is too shallow and with a slight movement of the camera or the model, you are out of focus, even if the movement is not there, the focusing range will be limited because of the model face structure and the clearances of the face different parts.<br>

All of my street portrait work done with providing enough clearances to obtain a nicely blurred background and at minimum of F5.6 with a mono pod used also.</p>

[photo5]

<p>I did research into the 500cm body focus issues. Apparently the mirror is mounted to the frame that holds it with some pads and adhesive, that over time will degrade causing the mirror to fall out of alignment slightly, causing an error in focus. You can easily test body focus using a newspaper. I did this with two 500cm bodies I had at the time, and both were slightly off at close range.<br>

I believe this problem can be fixed by a Hasselblad technician such as David Odess. He will do an overhaul to the body for a nominal fee.<br>

It is one more reason to purchase a newer Hasselblad body such as the 501c or 501cm.<br>

I have since sold all my Hasselblads as I prefer the twin lens Rolleiflex when I want to shoot the square. But I love Hasselblad and it is a superb photographic tool.</p>

[joseph_oxandale]

<p>Willy, I have had the exact same problem with the exact same camera. Did you find out conclusively what the problem was? I'd very much like to know.</p>