Sharpness with digital back/technical camera combos

[Edmund Sumner]

Hello

I wonder if anyone else has sharpness issues with digital backs and technical cameras

I use a leaf aptus 75 with Arca swiss and a worrying amount of images seem to go soft, I focus over and over but it seems a reoccurring problems especially with the wides, is there an optimum f stop I should be using?

Maybe this is down to lenses (digital vs film) but it seems anything from 90-480 is pin sharp but 72-58-47-38 cause me problems

Are digital lenses really much sharper?

I shoot architecture and design worldwide and also find I need to stitch extensively

Finally I am looking for a recommendation to replace my 47xl with a digital lens, which is the best?

edmund
www.edmundsumner.co.uk

[adammork]

Hello

I wonder if anyone else has sharpness issues with digital backs and technical cameras

I use a leaf aptus 75 with Arca swiss and a worrying amount of images seem to go soft, I focus over and over but it seems a reoccurring problems especially with the wides, is there an optimum f stop I should be using?

Maybe this is down to lenses (digital vs film) but it seems anything from 90-480 is pin sharp but 72-58-47-38 cause me problems

Are digital lenses really much sharper?

I shoot architecture and design worldwide and also find I need to stitch extensively

Finally I am looking for a recommendation to replace my 47xl with a digital lens, which is the best?

edmund
www.edmundsumner.co.uk

when I switched from film to digital, I start using my Arca Monolith and Misura and discovered the same thing as you, I could not get consistent focus with the wides - the standards was not parallel enough, and the focus gearing not as fine as you could wish. The lensboards was not consistent in thickness as well, some sat firm others rattled quite a bit. All this gave no practical troubles when using film - but digital is a complete other storie when talking tolerances, I'm on Alpa's now.

I also started with film lenses but they are all digital versions now, they are sharper but more importen IMO is the lack of CA.

Give the Schneider Apo-Digitar 47mm xl a test - it's really sharp, practical free of CA and distortion and have a nice huge image circle that covers the full movements on the Alpa XY.

/adam

[Edmund Sumner]

when I switched from film to digital, I start using my Arca Monolith and Misura and discovered the same thing as you, I could not get consistent focus with the wides - the standards was not parallel enough, and the focus gearing not as fine as you could wish. The lensboards was not consistent in thickness as well, some sat firm others rattled quite a bit. All this gave no practical troubles when using film - but digital is a complete other storie when talking tolerances, I'm on Alpa's now.

I also started with film lenses but they are all digital versions now, they are sharper but more importen IMO is the lack of CA.

Give the Schneider Apo-Digitar 47mm xl a test - it's really sharp, practical free of CA and distortion and have a nice huge image circle that covers the full movements on the Alpa XY.

/adam

thanks adam

CA ?

problem with alpa is I like to use long lenses 480 etc

any ideas

[Edmund Sumner]

RODENSTOCK 35mm f4.5 APO SIRONAR DIGITAL

is the above lens any good ?

Edmund

[adammork]

thanks adam

CA ?

problem with alpa is I like to use long lenses 480 etc

any ideas

CA = chromatic aberration

I had a hard time getting sharp images with my 240 and 360mm lens as well, on the arca's with a digital back, due to shutter vibrations from the big shutters on those lenses...

[ced]

CA is Chromatic Aberration...

[rainer_v]

RODENSTOCK 35mm f4.5 APO SIRONAR DIGITAL

is the above lens any good ?

Edmund

Mediocre to say the best. No comparation to its 35mm HR counterpart.

[Edmund Sumner]

Mediocre to say the best. No comparation to its 35mm HR counterpart.

hello rainer

thats the schneider ? 35mm hr

[JdeV]

when I switched from film to digital, I start using my Arca Monolith and Misura and discovered the same thing as you, I could not get consistent focus with the wides - the standards was not parallel enough, and the focus gearing not as fine as you could wish. The lensboards was not consistent in thickness as well, some sat firm others rattled quite a bit. All this gave no practical troubles when using film - but digital is a complete other storie when talking tolerances, I'm on Alpa's now.

I also started with film lenses but they are all digital versions now, they are sharper but more importen IMO is the lack of CA.

Give the Schneider Apo-Digitar 47mm xl a test - it's really sharp, practical free of CA and distortion and have a nice huge image circle that covers the full movements on the Alpa XY.

/adam

I've been researching this intensively recently.
Last week I visited Alpa and Sinar in Zurich and today I just got back from Besancon where I saw Arca.
I will write a longer post in the next few days but I think it should be noted, prior to any discussion of engineering tolerances, that a ground glass does not resolve enough for critical focus with a high resolution medium format back. (I've been quoted 1-6 l.p.m at best).
A more powerful lupe will just get you more glass grain because there isn't more detail to be got. In this respect it doesn't matter how accurately machined your camera is. Of course wider lenses and apertures only make the problem more apparent.
Interestingly, Arca told me that they tested finer focus gearing with ground glass focusing but found that it made accuracy worse because the eye tires quickly and we become more inaccurate when it takes longer to go backwards and forwards around the focus point.

[CBarrett]

The HR line is Rodenstock's.

Rainer, you get any movement out of the 35HR?  I understood they had a much smaller image circle.  Then again, I can't shift my 35 more than 7mm before I get diffraction softness.

[ThierryH]

thats the schneider ? 35mm hr

That's the Rodenstock. HR is solely used by Rodenstock lenses.

Thierry

[adammork]

In this respect it doesn't matter how accurately machined your camera is.

The biggest challenged I had with the wide-angels on my Arca's, was to get even focus on the entire sensor plane - here do accurately machined camera matter a bit  

Just for the record, I loved my Arca's as long there was film in it - especially the Misura

[JdeV]

Hello

I wonder if anyone else has sharpness issues with digital backs and technical cameras

I use a leaf aptus 75 with Arca swiss and a worrying amount of images seem to go soft, I focus over and over but it seems a reoccurring problems especially with the wides, is there an optimum f stop I should be using?

Maybe this is down to lenses (digital vs film) but it seems anything from 90-480 is pin sharp but 72-58-47-38 cause me problems

Are digital lenses really much sharper?

I shoot architecture and design worldwide and also find I need to stitch extensively

Finally I am looking for a recommendation to replace my 47xl with a digital lens, which is the best?

edmund
www.edmundsumner.co.uk

This is a general problem, it isn't you.

Optimum aperture with your film lenses will be F11-F16. They will have been designed to shoot at F16-F22. Digital sensors are much smaller than the film you would formerly have shot on but they can resolve much more per square mm. However, to match or exceed the resolution of the larger film area they require higher resolution lenses.
Because diffraction limits even the best lenses at smaller apertures to resolutions less than the sensor is capable of resolving, one needs to shoot with lenses optimised for F5.6-F11 where the ceiling on sharpness is not diffraction but engineering/cost. Larger image circles are also more challenging to achieve with lenses at these higher resolutions.

To ensure focus you need to employ a focusing system that does not rely on the ground glass. So you need to measure distance then transfer it to the lens somehow or you need to use trial an error and keep checking with a laptop.

The Rodenstock 50mm HR W or the 40mm HR W are incredibly sharp lenses that may suit your needs. They are mild retrofocus designs which means that they are able to be used further away from the ground glass than traditional symmetrical lenses and are brighter and more even. They have 90mm image circles. Their downsides are cost and some increase in distortion. Schneider have a 45mm (or thereabouts) coming out with a 110mm image circle I believe. I understand it is a symmetrical design. Based on my experience and my limited knowledge of optical design this lens will be very sharp but not as sharp as the Rodenstocks. It will have less distortion, more light fall-off, will be at its optimum at F11 and will need to closer to the ground glass to achieve focus. It will also be cheaper but not remotely cheap.

[BrianWoolf]

Hi Edmund,

Would this be your problem, you might have taken your first photo and it is sharp, but then you are unable to get the second or third photo as sharp as the first, even though you might focus multiple times.

I have something that might help, simple to do, does not take much time.

I am assuming that since you have a Leaf back, you are using Leaf Capture 11. In my set up of LC11, I have a small 100% window in the bottom left.

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% window and as soon as the 2nd exposure has processed, it should be sharper or a little more out of focus. If it is sharper, you have probably hit the focus and another micro-adjustment in the same direction may not increase the focus. If the 2nd exposure is softer, you probably chose the wrong direction. Simple make two micro-adjustments in the opposite direction and take a 3rd exposure. Check the 100% window and hopefully it is sharper than the first exposure. If the first exposure is the sharpest, it might simply be your lens.

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.

This is a way to refine your focus and achieve critical focus, it is very difficult to use if your focus is way off.

I hope this is clear and understandable.

Good luck,
Brian Woolf

[rainer_v]

The HR line is Rodenstock's.

Rainer, you get any movement out of the 35HR?  I understood they had a much smaller image circle.  Then again, I can't shift my 35 more than 7mm before I get diffraction softness.

on a 36x48mm sensor you can move the 35HR 12mm horizontal up till vignetting appears.
the lens is tack sharp till the image circle edge even at f4 and does not need a center filter.

you can move the rodenstock digital 35mm as well as the schneider 35mm digitar way more, but sharpness decrease drastically if moved more than 10mm and both lenses need to be stopped down at least 2 stops, are softer at the edges and show more vignetting.

distortion is a bit better with the schneider 35 ( its perfect ) but with the 35HR its  still very good
and i dont remember a shot where i saw it necessary to correct it in the 35HR in post.
i had some time in my "mf-beginner-days"the 35 digital rodenstock, didnt liked it and exchanged it for the 35HR.

[CBarrett]

on a 36x48mm sensor you can move the 35HR 12mm horizontal up till vignetting appears.
the lens is tack sharp till the image circle edge even at f4 and does not need a center filter.

you can move the rodenstock digital 35mm as well as the schneider 35mm digitar way more, but sharpness decrease drastically if moved more than 10mm and both lenses need to be stopped down at least 2 stops, are softer at the edges and show more vignetting.

distortion is a bit better with the schneider 35 ( its perfect ) but with the 35HR its  still very good
and i dont remember a shot where i saw it necessary to correct it in the 35HR in post.
i had some time in my "mf-beginner-days"the 35 digital rodenstock, didnt liked it and exchanged it for the 35HR.

Thanks Rainer, I've been struggling with the Rodenstock Digital 35 for 3 years, never trusting it to more than 7mm of movement.  I think I'll swap it out for the 35HR, I use this focal length a LOT.

Brian, that's the exact same thing I do with my Arca, amazing what a difference half a millimeter on the rail can make!

Now back to working on files...

[MHFA]

I've been researching this intensively recently.
Last week I visited Alpa and Sinar in Zurich and today I just got back from Besancon where I saw Arca.
I will write a longer post in the next few days but I think it should be noted, prior to any discussion of engineering tolerances, that a ground glass does not resolve enough for critical focus with a high resolution medium format back. (I've been quoted 1-6 l.p.m at best).
A more powerful lupe will just get you more glass grain because there isn't more detail to be got. In this respect it doesn't matter how accurately machined your camera is. Of course wider lenses and apertures only make the problem more apparent.
Interestingly, Arca told me that they tested finer focus gearing with ground glass focusing but found that it made accuracy worse because the eye tires quickly and we become more inaccurate when it takes longer to go backwards and forwards around the focus point.

Focusing on the groundglass is in my opinion not good enough for focusing. I think ALPA and the Artec took the right way in not using groundglass. Critical focus via live view. After half a year I had no more problems than with film. For me the Arca Swiss R3D is to complicate and slow.
Next weeks I will test the new Linhof. An infinity stop like the technikas would be fine, but I don`t think it can be exactly. The Linhof technicans told me that in their opinion the focusing like the Artec is not as good as groundglass focusing. They tested a lot of new glasses and will have a very fine one.
We will see...




Edmund, don`t stitch, use a 23HR or 28HR, wonderful lenses...

Michael Heinrich

[Gary Ferguson]

The Rodenstock 50mm HR W or the 40mm HR W are incredibly sharp lenses that may suit your needs. They are mild retrofocus designs which means that they are able to be used further away from the ground glass than traditional symmetrical lenses and are brighter and more even. They have 90mm image circles. Their downsides are cost and some increase in distortion.

Agreed. I use one of the new Rodenstock 40mm Digaron W lenses with a P65+ and a Linhof M679cs. It's a fantastic lens, noticeably better than the Rodentock 35/45/55m Digital lenses I was using before. Furthermore, the 90mm image circle seems a bit conservative, I've been able to stitch with the sliding back.

[Rob C]

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

[Edmund Sumner]

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

Rob

Valid question but no I have been working in this manner for a very very long time and generally had no problems in this regard, its a common problem form what I have heard so am interested to hear others experience

best


E