Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: douglevy on May 19, 2014, 08:50:17 pm
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So I've been shooting with the h1 since January, and can't seem to consistently nail focus. I'm shooting with a tripod for most of it (now) and seem to struggle anytime I'm wider than f/8. I'm using mostly the 50 and 80. Tips? Or just more practice? Thanks!
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You may already be doing this but...
Set the Camera to Manual focus. Set the user button to "AF Drive". Frame for focus (i.e. put the focus brackets on the eyes) and press the user button, then re-compose and shoot. Once you get used to it the AF is very good (granted it is only single point).
There is a margin of error when doing this depending on degree of movement, focal length, technique etc. These issues are mostly corrected by Hasselblad's True Focus system (which you don't get on an H1 alas).
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Thanks, and yes, I do that, holdover from shooting that way on my Nikons. There may be a h4x in my future, but I'm kinda hoping for an h6x with even 10-15 focus points.
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You might want to get that checked out. I use an H3DII (no True Focus, as with your H1), and I find the focus to be very good. Even with only one central focus point, even with focusing and recomposing.
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I´ve been shooting Contax 645 with mfdb for a couple of years either on a tripod with cable release or on a monopod and still have more trouble nailing focus than I ever did with any DSLR... for many reasons one of which is what is out of focus is much easier to pixel peep on an mfdb file, and another is to be rich enough to play with mfdb rather than dslr I had to wait until I was old enough my eyes don´t work so good... though your problem more likely can be blamed on the camera and buying a more expensive one with gizmos like true focus is sure to fix it.
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I'm not sure I follow your point. I'm conceding the problem is likely user error, not the camera.
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Hi,
Checking out if your AF works correctly is a good idea. The lens align target would be good for that.
Best regards
Erik
So I've been shooting with the h1 since January, and can't seem to consistently nail focus. I'm shooting with a tripod for most of it (now) and seem to struggle anytime I'm wider than f/8. I'm using mostly the 50 and 80. Tips? Or just more practice? Thanks!
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Thanks, and yes, I do that, holdover from shooting that way on my Nikons. There may be a h4x in my future, but I'm kinda hoping for an h6x with even 10-15 focus points.
I use H4 and H5 and would certainly not want that! TF works like a charm. Just concentrate on 1 focuspoin, focus and recompose to the desired composition. Sharpness is almost always where I want it. This works much more precise than any system that has even a lot of focus points. These points always seem to be in the wrong place for me no matter how many points I have.
If you get the hang of using TF you realize that having more than 1 focus point kind of defeats the purpose.
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Interesting. Thanks! I did some more testing, I really think it's just user error. I need to shoot slower, maybe at faster shutter speeds than I'm used to, and really slow my process down.
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I've found with the much larger viewfinder that I can usually spot focus problems in camera. If you're shooting at really shallow DOF though, I would definitely tell you to slow down and have your subject slow down in there too.
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Hey Doug,
Check and test your diopter adjustment. You might find like I have that a plus diopter adjustment will help you focus the lens more accurately.
Good luck,
Giorgio
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What Giorgio said. Adjust the diopter until the LCDs in the viewfinder are sharpest.
Also consider experimenting with the mirror delay as you might be seeing vibration induced softness?
Nick-T
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Hmmm. Did some more testing. Did some more testing. I think it might actually be the camera (very frustrating). 40+ photos of one of my dogs sitting still, ISO 50 and 100. When I look at them in C1 with focus mask turned on, it's consistently front focusing. (See attached screen shot with focus mask turned on). These are all at 2.8, yes, but I'm reactivating focus each time, and she's not moving. True, I was shooting handheld, but with 1/500 (80mm lens), I'd think these should be sharp. My technique isn't THAT bad. This is even more annoying because the camera was cleaned and checked by a local Hassy authorized repair place in February.
Thoughts? Thanks for the continued help.
-Doug
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Hi Doug
I'm not a C! user but seems to me the sharp bits are in line with the dog's eyes?
I would set up a controlled test. Camera on tripod, decent shutter speed and point 45 degrees down at a ruler and see if it's focussing where you think it is. This will confirm if the camera is front focussing. You could also test various mirror delay settings.
HTH
Nick-T
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I think 50ms mirror delay is the default. I have always set that to 100ms. As Nick suggested, try a controlled setup to find out whether your HB is front or back focussing. A matter of deduction, if the body is not front or back focussing, it might be user error.
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Definitely up that mirror delay to at least 100ms. The mirror packs a hell of a whallop.
The Hasselblad always seemed a bit poor at getting correct focus when you have to recompose. The H4 with True Focus though, mindblowing.
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Thanks everyone, will do a test here shortly. How does true focus work if you do more than focus and recompose, but change the distance to the subject slightly? Seem inevitable? Maybe a different topic, but just wondering.
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That's a good point Doug and yes if you move when re-composing then you are going to effect the plain of focus. I was a beta tester for True Focus and we looked at this, in my case and for whatever reason I don't move back and forth much when re-composing but this probably varies with the individual.
As others have said True Focus works very well.
Nick-T
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Well now I'm just as confused as before. The shot of my wife, focus point on her eye, is definitely out, the shot of the colorchecker/ruler looks in (focus point was put on the 6). Both shot from tripod, shot of Jes sis at F/4 and still looks out.
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(focus point was put on the 6).
Looks focussed in front of the 6 (@ 5.5) no?
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my point is I have found nailing focus with legacy mfdb is harder than dslr and concluded there may be no technical solution
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Probably. It's tough ton tell but it seems or be consistently front focusing. Focus in shots of Jess is on her hair.
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That's the thing. It's a brand new credo40. Old h1.
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The H1/H3 focus can be extremely accurate, but is not perfect. There are two things that bug me about it:
- it is a bit slower than it appears. Often, it first locks but not quite on the spot and, if you wait a few tenths of second longer, will then adjust a bit. If you don't wait these tenths of second, your focus will be a bit off.
- indeed sometimes it simply front focus a little bit and stays there. This happens more often in poorer light or when the patch of subject has less contrast or has some extension in depth.
Fortunately, the viewfinder on the H line is gorgeous. When I pay attention to the focus on the ground glass or focus manually, I can catch the occasional front focus error.
Then, if your camera consistently front focusses, the back may be at the wrong distance. The back resides on 4 metal patches around the sensor area. These surfaces are machined at a very precise height. You may want to clean them and mount/unmount your back a few times to make sure it is correctly set.
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Focus looks to be on 5.5 (as Nick said) and not on the 6. If 6 was what you were aiming for than the combination is definitely front focussing. Your image of the face seems to confirm that. It looks like the eyebrows are in focus and not the eyes.
If you can get hold of another body to try, it would be good to find out if this issue is in the body or back.
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I emailed hasselblad service yesterday and they recommended updating my firmware, I wonder if old fw/new back could be it. Will also try cleaning contacts. Thanks!
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It seems if your focusing is consistent in the same amount in front with 40 shots of your dogs, and you do get sharp shots, then you can rule out mirror shake, diopters, eyesight, and all that stuff and concentrate on a camera adjustment issue. Reading that you have a new Credo on an H1, I'd be looking at the sensor spacing as the culprit. A small difference in the sensor placement will cause this kind of consistent error. If your shots are consistently front focusing then the sensor spacing is too big - too far away from the camera. Ideally you'd get your sensor spacing adjusted by Leaf via your dealer, but its also possible to fix this issue by adjusting your camera - focusing screen and whatever tuning is required for the HB autofocus. And its also possible that your camera focus screen is out of adjustment. To rule that out you could check the following - see if your autofocus consistently focuses to the same spot your eye does, and also shoot some film with a film back to see if the focus manually by eye is accurate on film.
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Actually, good idea, I have an older back, will do a few more tests.
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I did a few calculation to find out what error would be necessary on the back adjustment to get the kind of error you seem to have. Let us say that you have a 100 mm lens, focus 2 m away and get a front focus of 2 cm. Using Descartes formula ( 1/p+1/p'=1/f ), I find that the back is 50 µm too far. That is about half the size of a human hair.
If you talk to a machinist, you will find that milling the contact surfaces between your camera and the back with a precision of 10 µm is an achievement and that temperature drift will probably mean your surfaces are not at the 10 µm position that is necessary. Maybe the camera AF electronics take temperature drift into account, I don't know.
Anyway, the message here is that AF accuracy is dependent on the four shining metal squares around the sensor on your back and on your camera are positioned with an accuracy of 10 µm or better. Obviously, any dirt on these pads will have some thickness, move your back away from where it should be and cause some front focus error. You don't need much dirt to be 10-20 µm thick, 10 µm is a tenth of a human hair size.
If everything is clean and you have mounted and dismounted your back a few times to insure that these 4 surfaces are correctly mated and you still get front focus, I would ask the back manufacturer, since you said that your camera has been adjusted recently. In the back, there are positioning screws to move the sensor a tiny bit forward. With the right equipment, this is a trivial adjustment.
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Same setup as last night, P25+. Tack sharp. Looks like a back issue.
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She looks pretty focussed to me...
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That's my point. I shot that with the p25+ not the new credo that is apparently chasing the issues. Going to capture integration tmrw.
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Thanks for all the help everyone. Spent the morning with Louis and Dave at Capture Integration and the camera's going to Hasseblad for repair.
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Update, camera went off to Hasselblad to fix, $600 in repairs.
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Update, camera went off to Hasselblad to fix, $600 in repairs.
Thank you, but what was the issue? Autofocus or the spacing studs?
Sounds more serious than either as fixed price autofocus calibration is £162 UK pds +VAT + carriage, contact pins (? spacers or electrical) £203, here in he UK, well not here exactly when done in Sweden ;)
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All new lens mounts, new focusing screen, new mirror, full cleaning, firmware update
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All new lens mounts, new focusing screen, new mirror, full cleaning, firmware update
A wonder it was working ;D
Appreciated.
I have just sent a H1 off for focus check, no issues but is early firmware as well and only a film back available. Cheaper to send to Sweden than rent a back for a day. Hoping they don't come back with that kind of bill.