Sharpness with digital back/technical camera combos

[ThierryH]

Rather than the problem of focussing wide-angles being due to the camera/back accuracy, especially when the same set-up works well with longer lenses, isn't it simply due to the fact that wides have a shallower depth of focus than do longer lenses, and as a result, you are either in focus or out of it much more rapidly if you make a mistake with your eye when using wides with groundglass screens?

More a problem of the operator than the optic?

Rob C

For what it is worth, I can only suggest to do as suggested by others: make a shot and check sharpness. If out, simply re-focus very very slightly forward or backward, by a fraction of a millimeter. That is where precise cameras are necessary, to allow those very fine and precise focus differences.
Why is it so difficult to have the right focus with short focal length lenses? Simply because even full open the DoF is already quiet important and it is difficult to really set the focus point right. If e.g one has already focus when full open from e.g. a few tens of meters to infinity, the it is easy to be wrong when the point to focus lies for example between this existing DoF when full open. But with time and the experience, this can be easily overcome.

Best regards,
Thierry

[Dick Roadnight]

Hi Edmund,

Set up and do a groundglass focus and take an exposure(the exposure is correct) check the focus in the 100% window. If it is not as sharp as you think it should be, do the following. Do NOT open the lens or refocus using the groundglass. Simply take your focusing knob on whatever standard you use and make a micro-adjustment, either forward or back, the standard should just barely move(I have a sinar p and do not have to lock focusing knobs ever). Advance the shutter and take a second exposure, watch the 100% ....

I use a 150mm Apo-Sironar(a film lens) on a sinar p, with a leaf valeo 17wi to photograph jewelry, so that the jewelry is reproduced at lifesize(100%) or larger on the page. I use this all the time to fine tune the focus on diamond rings, etc.


Good luck,
Brian Woolf

As suggested above, Live view helps, and in IMO it is what makes Medium Format Digital View Camera (MFDVC) photography viable with short lenses.

You will probably have to check the focus in several areas of the picture if you are using tilt, or if your tilt/yaw is not accurately set to zero.

¿Anyone using a Hasselblad back with live view on a MFDVC?

I am still waiting for live view for my system (below).

Why not get a Schneider apo-digitar macro for jewellery? (I was luck enough to pick one up on e-Bay.)

[Edmund Sumner]

As suggested above, Live view helps, and in IMO it is what makes Medium Format Digital View Camera (MFDVC) photography viable with short lenses.

You will probably have to check the focus in several areas of the picture if you are using tilt, or if your tilt/yaw is not accurately set to zero.

¿Anyone using a Hasselblad back with live view on a MFDVC?

I am still waiting for live view for my system (below).

Why not get a Schneider apo-digitar macro for jewellery? (I was luck enough to pick one up on e-Bay.)

are there any issues with stitching on digital lenses, the one good thing about film lenses is the images circle size

I guess I need 15-20 mm of movement all ways ?

also on an old post someone talked about reversing the rear standard of arca 6/9 to make it easier focus for wides and also using a Hasselblad RMfx - Viewfinder for focus

has anyone heard of this ?

many many thanks this is all super useful for me  

edmund
www.edmundsumner.co.uk

[Dick Roadnight]

are there any issues with stitching on digital lenses, the one good thing about film lenses is the images circle size

I guess I need 15-20 mm of movement all ways ?

also on an old post someone talked about reversing the rear standard of arca 6/9 to make it easier focus for wides and also using a Hasselblad RMfx - Viewfinder for focus

has anyone heard of this ?

many many thanks this is all super useful for me  

edmund
www.edmundsumner.co.uk

6 * 9 is a good size (e.g. sinar P3), and most Schneider apo-digitars (over 47mm) cover it... you can cover 6 * 9 with 3 of four shots, with camera movements or a sliding back.

Shift (or slide) and stitch is much better than pan and stitch.

[JdeV]

are there any issues with stitching on digital lenses, the one good thing about film lenses is the images circle size

I guess I need 15-20 mm of movement all ways ?

also on an old post someone talked about reversing the rear standard of arca 6/9 to make it easier focus for wides and also using a Hasselblad RMfx - Viewfinder for focus

has anyone heard of this ?

many many thanks this is all super useful for me  

edmund
www.edmundsumner.co.uk

There is no magic bullet with viewfinders etc. Focusing needs to be done in the manner suggested by several other contributors. Approximate with the ground glass, check on screen then make small movements of the focusing knob whilst checking with fresh exposures until accurate sharpness is achieved.

[JdeV]

Rather than the problem of focussing wide-angles being due to the camera/back accuracy, especially when the same set-up works well with longer lenses, isn't it simply due to the fact that wides have a shallower depth of focus than do longer lenses, and as a result, you are either in focus or out of it much more rapidly if you make a mistake with your eye when using wides with groundglass screens?

More a problem of the operator than the optic?

Rob C

Neither optic nor operator are at fault, the ground glass doesn't offer sufficient resolution to accurately place focus. Of course very shallow depth of focus compounds the issue.

[CBarrett]

Yes, you can reverse the standards on the F Line to focus the wide lenses, not necessary on the M Line or F Metric (as I recall).  Most of the 'Blad type viewers are much lower powered (3x or 4x maybe).

I use an 8x loupe and that gets me in the ballpark with a Maxwell Screen.

[jotloob]

also on an old post someone talked about reversing the rear standard of arca 6/9 to make it easier focus for wides and also using a Hasselblad RMfx - Viewfinder for focus
has anyone heard of this ?
edmund
www.edmundsumner.co.uk

Yes , it was me .
The one fold leather wide angle bellow for the ARCA did not have enough room for movements .
If you reverse the rear standard , then the bellow has enough room to move , when using wide angle lenses .

As I have two HASSELBLAD V-SYSTEM adaters for the ARCA 6x9 , I found it very useful to focus , using the groundglas adapter (normal or SWC) + the RMFx .

Jürgen