Focusing questions on the 645ProTL

[carrie_geddie]

<p>I recently got a 645 Pro TL with the 80 f/1.9. I also have the AE prism. Just got my first rolls back from the lab and many, but not all, of the images are out of focus. I previously had the RZ67 + prism and was able to focus that without a problem.</p>

<p>I focused by essentially lining up the top and bottom of the thing in the center of the prism (sorry I don't know the right term), then would recompose. Is this wrong? It seems that the distance I focus on should end up being what's in focus after I recompose... Can I get some tips and tricks from any veterans?</p>

<p>I also read that it's possible my film wasn't wound tight enough. For example, of the 3 rolls, one roll had only 14.5 frames (a 120 roll). The 15th frame was only half the image... so now I'm wondering if not loading it tight enough (or something else) was part of my problem. Any tips for getting the film totally snug on the insert?</p>

<p>And lastly, I have my lens set so the M is showing - I know it's supposed to be on M for manual focusing, but does that mean the M is showing or is covered?</p>

<p>Thanks in advance for helping out a newbie who's feeling like an idiot b/c I can't get my focus right. </p>

<p>Carrie</p>

[jim_peterson2]

<p>A couple of things to point out. First, about the last point you make; the M and A switch on the lens has nothing to do with manual focusing. This switch determines whether the aperture blades close as you stop down the aperture ring or whether they stay open until you actually release the shutter. You should always leave it on A unless you want to check DOF. That will allow you to compose and focus with the lens wide open and then it will close down when shooting. In M mode your view in the finder will get rather dark if you stop the lens down, making it difficult to focus so that could be part of your problem. If you are shooting with the metered prism finder in aperture priority mode you must have the lens set to A mode or your exposure will be wrong (unless you are shooting everything wide open)<br>

The second point is that if you are shooting that lens wide open, at f/1.9 or there abouts the DOF is extremely shallow, making accurate focusing very difficult. You can check any of the online DOF calculators to figure out exactly how shallow it is.</p>

[brendan_odonohue]

<p>Carrie, I also have the 80mm 1.9 on my Mamiya, and forgive me if I'm pointing out the obvious here, but with an aperture of 1.9 on a MF camera, the DOF is so shallow that when you do as you say you are doing, and focus with the center circle and then recompose, you are often going out of focus on your intended subject simply by recomposing.<br>

I tried to get used to focusing without using the center part of the prism, so that allowed me to compose as I wanted, and then attempt to get best possible focus on my subject with them in place. I have the 85mm 1.2 for my Canon, and I'd had to get used to the very same way of focusing with that lens when wide open.<br>

When you view the neg, does it show areas immediately in front or behind your intended focus target to have more accurate focus? If so, it might just be the recompose issue, if not it could well be film flatness if the entire image is OOF. (Unless of course it's camera shake which I doubt at 1.9!) <br>

Even when you don't focus/recompose, it's still a pretty difficuly lens to hit focus on all the time!<br>

Bren</p>

[ondebanks]

<p>I think that you're being caught out by the combination of the very slim DOF at f1.9 and the geometric focus shift that occurs when you recompose. If you want to focus on off-centre subjects, and shoot them at wide apertures, I would recommend avoiding the focus-recompose approach: instead use the matte/fresnel area of the screen directly on the subject where possible. Replacement all-matte (or all-matte + grid) screens are cheap and would make this even more accurate than the stock screen.</p>

<p>Re. film loading tips...do you have a user manual for the camera? You can find it on the Mamiya-Leaf website in their legacy products section.</p>

 

<blockquote>

<p>the thing in the center of the prism (sorry I don't know the right term)</p>

</blockquote>

<p>It's a split-image prism rangefinder.</p>

[jim_momary]

<p>See here for depth of field ...<br>

<a href="http://www.dofmaster.com/dofjs.html">http://www.dofmaster.com/dofjs.html</a><br>

Select 6x4.5 film, 80mm, and a distance.<br>

Let's presume 5.0 feet for the subject distance.<br>

F stop ----- DoF (inches)<br>

1.9 --------- 2.3 inches<br>

4 ----------- 4.9 inches<br>

8 ----------- 9.8 inches<br>

16 ---------- 20 inches<br>

The larger the film/sensor format, the shallower is the depth of field for a given aperture.<br>

That may be what bit you in conjunction with the recomposing as mentioned above.<br>

Jim</p>

 

[carrie_geddie]

<p>I cannot thank you all enough for this. It is so disheartening to not do something well, although I know medium format is a new experience and the whole point is about learning and challenging myself. But still, the learning curve is hard to take! :-)</p>

<p><strong>Jim</strong> - Okay, this is so incredibly helpful. I had read/been told to leave it on M, but this makes so much more sense. And I just made that change to A and could see the focusing screen get brighter, so that will definitely help! I was actually shooting with an external meter at the time, so I will remember to leave it on A for when I do use the metered prism.</p>

<p><strong>Brendan</strong> - yes, I knew in my head that I had no more than 2" to screw up focus and knew it would be tight, I think I didn't fully comprehend how the focus worked. I think the advice to focus with the entire focusing screen is going to be key for me. Coming from digital with a ton of focus points to choose from, I have some bad habits to break.</p>

<p><strong>Brendan & Ray</strong> - I did bookmark the manual online and read it for loading tips. Had everything lined up right and the spool taut but there is one image on one roll that was completely OOF. If it was just one image on the roll, do I assume it was my focusing issue and not slack in the roll? Also, the 15th images on two rolls were not an entire frame - ie, half the image is white - so I am clearly doing something wrong since I should expect to get 16 frames per roll, correct?</p>

<p><strong>Ray</strong> - great idea about a new (brighter) focusing screen. Do you have one you can recommend? KEH.com has "A Matte"and "A4 Checker" as two options..... </p>

<p>Again, thank you all SO much. Any other thoughts are, of course, appreciated!</p><div></div>

[carrie_geddie]

<p><strong>Ray</strong> - okay, the "checker" is the grid. I am ordering one now, ha ha!</p><div></div>

[ondebanks]

<p>That's a lovely shot.</p>

 

<blockquote>

<p><strong>Ray</strong> - okay, the "checker" is the grid. I am ordering one now, ha ha!</p>

</blockquote>

<p>Yes, that's the one I meant. The grid lines help with keeping the horizon level, architectural shots etc., so it's handy to have them. In every other respect it's the same as the plain matte screen.</p>

<blockquote>

<p>there is one image on one roll that was completely OOF. If it was just one image on the roll, do I assume it was my focusing issue and not slack in the roll?</p>

</blockquote>

<p>Hard to diagnose why you got only one image on one roll that was completely OOF. Slackness in the film would surely affect more than one frame. Was this when you were shooting with the lens set to "M" rather than "A"? Perhaps it was too dark (stopped down too much) to focus properly?</p>

<blockquote>

<p>the 15th images on two rolls were not an entire frame - ie, half the image is white - so I am clearly doing something wrong since I should expect to get 16 frames per roll, correct?</p>

</blockquote>

 

<p>You should get 15 images with a ProTL. (The later 645AF camera series give 16 frames per roll). But getting half of the 15th image white sounds to me like you unloaded the film before fully winding it on to completion, accidentally exposing part of the last frame to ambient light? There is a significant amount of black paper trailer to wind off after the 15th exposure. You can hear, and if you are winding by hand you can feel the tension change, when the film is truly finished i.e. the last bit of paper leaves the supply spool. Only open the back then, and keep the finished roll tightly wound as you removed it (I always give mine a twist by hand before sealing it with the gummed paper).</p>

 

[carrie_geddie]

<p><strong>Ray</strong> - Regarding the OOF image, unfortunately I can't remember whether the lens was set to M or A, but maybe I just just completely blew that one!</p>

<p>I will attach the 15th frame of the roll so you can see. Your description of the problem makes perfect sense, if I were winding by hand. But, I have the power grip winder. So, when the last frame is shot, it automatically rewinds. The roll feels pretty tight when I remove it and then I go ahead and lick the roll closed, but maybe I am exposing it. Man, that's rough! I shot 3 rolls and the last frame on two of the rolls did this. Got to be user error, sigh...</p>

<p>Thanks again, you guys are really making me feel like these are things I can correct and that with practice, I will get a much higher rate of "keepers" like I do with my 35mm!</p><div></div>

[philip_wilson]

It seems like Ray has got you on the right track. The only other thing you may want to ensure is that all the mechanical

interfaces are clean. The DOF of this (great) lens at F1.9 is very shallow so any slight displacement of the back, film

holder or focussing screen can cause a slight change in the focus. If your problems wide open persist check that the

focussing screen is seated correctly and that the back and insert are mounted spot on.

[carrie_geddie]

<p>Thanks <strong>Philip</strong>. I will double check all that and get a new (brighter) focusing screen, then try a few rolls again... At least I'm encouraged now! </p>

<p>Thanks to everyone for their feedback/help!</p>

[Mike Gammill]

<p>If it is possible to borrow another lens from a Mamiya 645 user or visit a shop that has some in stock you might try a few shots with other lenses (like the 80mm f2.8, 70mm LS, or maybe one of the short teles) just to make sure that there are no issues in the camera. I own two Mamiya 645E's and a 645 J (with waist level finder and microprism screen) and never have any focus problems.</p>