Infinity Focus on Hasselblad 500CM

[shane_mullins]

<p>Hi,<br>

I recently acquired an old Hasselblad 500cm with some lenses (all CF 80, 50 and 150mm). I've noted that when I set a lens onto the infinity setting and look through the viewfinder at a distant object, the focus is a slightly out. It requires me to focus back slightly to bring distant subjects into sharp focus. It that going to present me any problems? If a subject appears in sharp focus in the viewfinder is it actually in sharp focus? I have not processed any films from this camera as yet to scrutinise for any issues. </p>

<p>Thanks,<br>

Shane</p>

 

[mukul_dube]

<p>If this happens with all lenses, the optical system of the camera body may be out. The sharpness of pictures on film will depend on what is meant by "slightly".</p>

[Ed_Ingold]

<p>It's possible that the focusing screen is not aligned with the plane of focus. There are leveling screws for the screen, lacquered in position. Don't touch them until all other possibilities are exhausted, and leave them to a qualified technician.</p>

<p>Are you using an Hasselblad focusing screen? Is it upside down (the top side is shiny. All grids and lines are embossed on the bottom).</p>

<p>The most likely cause is your own eye. Some focusing screens are more transparent than others, for brighter viewing. You can look through them and focus on a virtual image if you're not careful. Take care to focus your eye on any grid markings, or the faint pattern of the Fresnel lens, before focusing the lens.</p>

<p>An adjustable finder is ideal if your eyes (like mine) are not as adaptable any more. A PM90, PM45 or chimney finder works well. You can also fit a waist level finder with a corrective lens. The waist level finder actually has the highest magnification (about 5x), but not as corrected as the finders mentioned above.</p>

<p>Hint: if the subject is far away, but the best focus is just short of the infinity stop, trust the lens stop not your eye.</p>

[shane_mullins]

<p>I have a split focusing screen and it comes into sharp just short of the infinity stop as you have said. I think I'll run some checks after developing some film and checking out the results then. I'll shoot a roll of portraits focusing on the eyes and see if they are sharp.<br>

Thanks for the tips so far...much appreciated. I'm also impressed with the quick replies in this forum.</p>

[Ed_Ingold]

<p>George Washington once said "You learn from experience. Unfortunately, you gain experience by making mistakes."</p>

[savagesax]

Well the above answers could solve your problems. It's also possible, but highly unlikely that the mirror hinges

are hanging up or out of adjustment, bent slightly if the mirror hung up and a past owner tried to force the

mirror back into position, but you would know this by every photo being out of focus and also having difficulty

focusing at any range. It's possible that part of the photo may be sharper than another part. Again, highly

unlikely, but possible.

 

My first thought when reading the post is Mukul's comments. Is this with all of the lenses? If so, my guess is

it's surely a problem with the CM body, including the focusing screen, not the lenses.

 

I've always liked bright screens, not the standard Hassy screens. So when getting a new/used camera body I

always changed out the screens. With the CM you simply drop the new bright screen in. No adjustments are

needed. This was a really great improvement from the 500 C bodies. With those C bodies you had to adjust all

4 corner screws. So knowing this perhaps a past owner of your camera messed around with these 4 screws?

 

When you do your portrait test try to use F11 on all of the lenses. With most lenses, not just Hasselblad lenses

F8 to F11 is often the sharpest settings of the lenses.

 

Keep us posted. This is an interesting issue.

[shane_mullins]

<p>After pulling the viewfinder off the camera I removed and replaced the focusing screen (it was already the right side up) put the viewfinder back on and now distant subjects are in focus. I will still run a film through the camera to confirm that I don't have any focussing issues. I really do appreciate you all engaging me on this matter and after what seems a very simple thing to do to apparently rectify this problem, I hope I have not wasted anyone's time in responding to me. </p>

[savagesax]

You surely don't have to worry about time wasted. I'm glad that it wasn't anything more serious! Have fun and

enjoy the great camera and the wonderful 3 lenses.

[pavel_l.]

<p>If you have some film left in your camera you can check front/back focusing by building a simple focusing set. Take a one foot wooden ruler and stick a needle on the middle. Place this ruler at ~30 degrees to horizon. Put your camera on tripod and position it at 5-8 ft from the needle (position of film is marked on magazine by "O" with vertical line) make sure scale on lens points to above (same) distance. Expose film under good light. Make sure the diaphragm is completely open. If you have exposed you test roll already, place camera 5-8 ft from target, adjust focus, than check the distance on the lens scale. My 2 cents.</p>