Discrepancy between focal point in EVF and recorded file when using adapted lens?

Noddemix said:

1. Noddemix wrote:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

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Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

Noddemix said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

Rob de Loe said:

Rob de Loe said:

1. Noddemix wrote:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

The FA version has an aperture ring. You can use the same adapter.

My understanding of the history of the lenses is that the optics are identical between A and FA on the 120. It comes down to how you like the focus ring on FA lenses.

Click to expand...

Rich42 said:

Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

It's a shame that there is apparently such variation in these lenses. When I bought mine, I already had quite a collection of Pentax lenses for my 645N, including 6x7 lenses and had no compunction about getting this one for "scanning" negs with my 100S. As far as I was concerned, Pentax didn't make any "iffy" gear.

Click to expand...

Rich42 said:

I jumped on the first one I saw on eBay (at a ridiculously low price) and have been very happy with it. I don't use it at all for general field work, but it performs beautifully in that range. It never leaves my enlarger/copy stand.

As long as you can return what you buy, I would continue to try obtain one that's working well. There are good copies, and they are worth the search for their 1:1 macro capabilities. For field work, my GF 110 keeps anything close to that focal length far, far away.

Click to expand...

Rich42 said:

Rich42 said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

Click to expand...

Noddemix said:

Rich42 said:

Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

It's a shame that there is apparently such variation in these lenses. When I bought mine, I already had quite a collection of Pentax lenses for my 645N, including 6x7 lenses and had no compunction about getting this one for "scanning" negs with my 100S. As far as I was concerned, Pentax didn't make any "iffy" gear.

Click to expand...

I'm not sure they do, but I guess we don't know what people have been doing with them the past few decades. Sometimes the roughest looking lenses are the best performing optically, and I have a theory that could be a pro using their gear heavily but also servicing/repairing when required.

Noddemix said:

I jumped on the first one I saw on eBay (at a ridiculously low price) and have been very happy with it. I don't use it at all for general field work, but it performs beautifully in that range. It never leaves my enlarger/copy stand.

As long as you can return what you buy, I would continue to try obtain one that's working well. There are good copies, and they are worth the search for their 1:1 macro capabilities. For field work, my GF 110 keeps anything close to that focal length far, far away.

Click to expand...

Same with my GF 120mm, brilliant for this short tele use case,

Click to expand...

Noddemix said:

but the Pentax being so off has me wondering if my copy should also be better on the copy stand.

Buying stuff from Japan can be a bit of a pain with customs, but needs must. I'm going to try an FA version I can source locally before I go looking on eBay again.

Noddemix said:

Noddemix said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

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Rich42 said:

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible.

Click to expand...

Rich42 said:

Who would have cared? That would not have influenced their use as they were intended.

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JimKasson said:

Rich42 said:

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible.

Click to expand...

I'm sure they were optimized for on-axis performance, as off-axis performance wouldn't have mattered in that usage.

JimKasson said:

Who would have cared? That would not have influenced their use as they were intended.

Click to expand...

Indeed.

Click to expand...

Rich42 said:

JimKasson said:

Rich42 said:

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible.

Click to expand...

I'm sure they were optimized for on-axis performance, as off-axis performance wouldn't have mattered in that usage.

Rich42 said:

Who would have cared? That would not have influenced their use as they were intended.

Click to expand...

Indeed.

Click to expand...

They were essentially, microscope objectives.

Click to expand...

JimKasson said:

Rich42 said:

JimKasson said:

Rich42 said:

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible.

Click to expand...

I'm sure they were optimized for on-axis performance, as off-axis performance wouldn't have mattered in that usage.

JimKasson said:

Who would have cared? That would not have influenced their use as they were intended.

Click to expand...

Indeed.

Click to expand...

They were essentially, microscope objectives.

Click to expand...

Then they probably did better off axis than the scanner application required.

Click to expand...

Rich42 said:

Noddemix said:

Rich42 said:

Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

It's a shame that there is apparently such variation in these lenses. When I bought mine, I already had quite a collection of Pentax lenses for my 645N, including 6x7 lenses and had no compunction about getting this one for "scanning" negs with my 100S. As far as I was concerned, Pentax didn't make any "iffy" gear.

Click to expand...

I'm not sure they do, but I guess we don't know what people have been doing with them the past few decades. Sometimes the roughest looking lenses are the best performing optically, and I have a theory that could be a pro using their gear heavily but also servicing/repairing when required.

Rich42 said:

I jumped on the first one I saw on eBay (at a ridiculously low price) and have been very happy with it. I don't use it at all for general field work, but it performs beautifully in that range. It never leaves my enlarger/copy stand.

As long as you can return what you buy, I would continue to try obtain one that's working well. There are good copies, and they are worth the search for their 1:1 macro capabilities. For field work, my GF 110 keeps anything close to that focal length far, far away.

Click to expand...

Same with my GF 120mm, brilliant for this short tele use case,

Click to expand...

Ah . . . Didn't realize you had the GF 120. Why then, even be concerned about the Pentax for distance?

Test the Pentax at 1:1, and if it meets your needs, that's the end of the story.

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible. Who would have cared? That would not have influenced their use as they were intended.

If you have a Pentax Macro that works well at macro range. Use it that way. Ignore every other characteristic of its performance.

Click to expand...

Rich42 said:

Rich42 said:

but the Pentax being so off has me wondering if my copy should also be better on the copy stand.

Buying stuff from Japan can be a bit of a pain with customs, but needs must. I'm going to try an FA version I can source locally before I go looking on eBay again.

Rich42 said:

Rich42 said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

Click to expand...

Click to expand...

--
Rich
"That's like, just your opinion, man." ;-)

Click to expand...

Noddemix said:

Rich42 said:

Noddemix said:

Rich42 said:

Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

It's a shame that there is apparently such variation in these lenses. When I bought mine, I already had quite a collection of Pentax lenses for my 645N, including 6x7 lenses and had no compunction about getting this one for "scanning" negs with my 100S. As far as I was concerned, Pentax didn't make any "iffy" gear.

Click to expand...

I'm not sure they do, but I guess we don't know what people have been doing with them the past few decades. Sometimes the roughest looking lenses are the best performing optically, and I have a theory that could be a pro using their gear heavily but also servicing/repairing when required.

Noddemix said:

I jumped on the first one I saw on eBay (at a ridiculously low price) and have been very happy with it. I don't use it at all for general field work, but it performs beautifully in that range. It never leaves my enlarger/copy stand.

As long as you can return what you buy, I would continue to try obtain one that's working well. There are good copies, and they are worth the search for their 1:1 macro capabilities. For field work, my GF 110 keeps anything close to that focal length far, far away.

Click to expand...

Same with my GF 120mm, brilliant for this short tele use case,

Click to expand...

Ah . . . Didn't realize you had the GF 120. Why then, even be concerned about the Pentax for distance?

Test the Pentax at 1:1, and if it meets your needs, that's the end of the story.

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible. Who would have cared? That would not have influenced their use as they were intended.

If you have a Pentax Macro that works well at macro range. Use it that way. Ignore every other characteristic of its performance.

Click to expand...

But I've no point of reference in terms of how good it is closer to MFD,

Click to expand...

Noddemix said:

and it's not anywhere near as good as the Sigma 105mm Art (E-mount) so naturally, I'm wondering if it could be better than I'm seeing since it has serious issues elsewhere. I also had an idea that I'd use it at distance if it was closer in optical performance to the GF 120mm, because I much prefer helicoid manual focusing over AF or the FBW implementation of the native lenses, but honestly that's moot because the focus throw does not lend itself to easy focusing at distance.

Noddemix said:

Noddemix said:

but the Pentax being so off has me wondering if my copy should also be better on the copy stand.

Buying stuff from Japan can be a bit of a pain with customs, but needs must. I'm going to try an FA version I can source locally before I go looking on eBay again.

Noddemix said:

Noddemix said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

Click to expand...

Click to expand...

Click to expand...

Click to expand...

Rich42 said:

JimKasson said:

Rich42 said:

JimKasson said:

Rich42 said:

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible.

Click to expand...

I'm sure they were optimized for on-axis performance, as off-axis performance wouldn't have mattered in that usage.

Rich42 said:

Who would have cared? That would not have influenced their use as they were intended.

Click to expand...

Indeed.

Click to expand...

They were essentially, microscope objectives.

Click to expand...

Then they probably did better off axis than the scanner application required.

Click to expand...

Hmmm . . .

Didn't mean they were standard, interchangeable, housed in the standard screw-on mounts available for clinical or scientific microscopes.

The "mounts" appeared quite proprietary to the scanner brands (Howtek, Heidelberg). I have no idea about the optics designs compared to standard ones, but they performed the same function in the same place in the typical optical path of a generic microscope.

Very small. Tiny.

(Did any of that make sense?)

Click to expand...

Rich42 said:

Noddemix said:

Rich42 said:

Noddemix said:

Rich42 said:

Noddemix said:

Thanks for your time Rob - I could definitely have picked a better scene as you can't really see how sharpness is distributed throughout the frame. I'll try again today using your post as a reference and see what I can come up with.

I've been reluctant to buy another as I've had bad luck sourcing a good copy of this lens. I bought one last year that was immaculate, looked like it had never been removed from the box, and yet it was completely de-centred, but at least in a way that made sense to me (unlike this one). I know Rich and I think left-eye(??) have both said their copies are superb, but I just haven't been able to find one yet.

Click to expand...

It's a shame that there is apparently such variation in these lenses. When I bought mine, I already had quite a collection of Pentax lenses for my 645N, including 6x7 lenses and had no compunction about getting this one for "scanning" negs with my 100S. As far as I was concerned, Pentax didn't make any "iffy" gear.

Click to expand...

I'm not sure they do, but I guess we don't know what people have been doing with them the past few decades. Sometimes the roughest looking lenses are the best performing optically, and I have a theory that could be a pro using their gear heavily but also servicing/repairing when required.

Rich42 said:

I jumped on the first one I saw on eBay (at a ridiculously low price) and have been very happy with it. I don't use it at all for general field work, but it performs beautifully in that range. It never leaves my enlarger/copy stand.

As long as you can return what you buy, I would continue to try obtain one that's working well. There are good copies, and they are worth the search for their 1:1 macro capabilities. For field work, my GF 110 keeps anything close to that focal length far, far away.

Click to expand...

Same with my GF 120mm, brilliant for this short tele use case,

Click to expand...

Ah . . . Didn't realize you had the GF 120. Why then, even be concerned about the Pentax for distance?

Test the Pentax at 1:1, and if it meets your needs, that's the end of the story.

The lenses in my drum scanners performed excellently at their fixed positions. I have no idea how they may have performed if they had been fitted for field work. (Who would have done that?) They probably would have been terrible. Who would have cared? That would not have influenced their use as they were intended.

If you have a Pentax Macro that works well at macro range. Use it that way. Ignore every other characteristic of its performance.

Click to expand...

But I've no point of reference in terms of how good it is closer to MFD,

Click to expand...

I'm not really clear why you say that.

My "frames of reference" have been comparison to my older drum scan results (the Pentax 120/100S system gives me equal or better results) and comparison to detail I can see examining slides and negs with a 10x/20x examination microscope.

Click to expand...

Rich42 said:

One of the frustrating things in the drum scanning game was occasionally dealing with customers who could see detail in slides that couldn't be retained in scans. Both detail and dynamic range.

It's always possible to see things "optically" that a scan of any kind can't hold.

You could use a microscope to give you a frame of reference.

Or you could buy a few drum scans (from one of the few services still extant) and compare with those.

Rich42 said:

and it's not anywhere near as good as the Sigma 105mm Art (E-mount) so naturally, I'm wondering if it could be better than I'm seeing since it has serious issues elsewhere. I also had an idea that I'd use it at distance if it was closer in optical performance to the GF 120mm, because I much prefer helicoid manual focusing over AF or the FBW implementation of the native lenses, but honestly that's moot because the focus throw does not lend itself to easy focusing at distance.

Rich42 said:

Rich42 said:

but the Pentax being so off has me wondering if my copy should also be better on the copy stand.

Buying stuff from Japan can be a bit of a pain with customs, but needs must. I'm going to try an FA version I can source locally before I go looking on eBay again.

Rich42 said:

Rich42 said:

I may try the Mamiya equivalent, or in fact there's a camera shop near me selling the -FA version of this. I have a Fotodiox adapter that I believe allows me to change the aperture on the FA lenses. Do you know if there's anything about the FA version that would mean it's not suitable for digitising negatives? I understand the A and FA are optically identical with the 7 group floating element design, but I wonder how the helicoid is compared to the A. It's rare that I hear people using the FA lenses on GFX

Click to expand...

Click to expand...

Click to expand...

Click to expand...

Click to expand...

--
Rich
"That's like, just your opinion, man." ;-)

Click to expand...

Noddemix said:

This strikes me as impossible, but is there any mechanism by which a Pentax 645 lens adapted to GFX can have an object in focus in the EVF, but the recorded file is slightly front focused?

I'm shooting wide open, using either full magnification or peaking (low) + magnification to focus on an object about 50m away, but when I open the file the sharpest area of the image is consistently a few meters in front of where I focus using the EVF.

The lens is stopped down to the taking aperture when focusing.

I'm not adjusting aperture or moving the camera in between focusing and taking.

The diopter is on the minimum setting and I have normal vision.

I'm not using my T/S adapter so there are no movements to worry about, and my understanding is that any issue with how the lens/adapter is interacting with the sensor would manifest in the EVF.

I've also been working on the assumption that the zone of acceptable focus is usually 1/3 in front of the focal point, 2/3 behind, which seems flipped around here.

What's going on? Could IBIS be playing a role? I haven't attempted to recreate with a tripod because I'm travelling without my tripods, perhaps should try again without IBIS.

Click to expand...

Alexander6x6 said:

Noddemix said:

This strikes me as impossible, but is there any mechanism by which a Pentax 645 lens adapted to GFX can have an object in focus in the EVF, but the recorded file is slightly front focused?

I'm shooting wide open, using either full magnification or peaking (low) + magnification to focus on an object about 50m away, but when I open the file the sharpest area of the image is consistently a few meters in front of where I focus using the EVF.

The lens is stopped down to the taking aperture when focusing.

I'm not adjusting aperture or moving the camera in between focusing and taking.

The diopter is on the minimum setting and I have normal vision.

I'm not using my T/S adapter so there are no movements to worry about, and my understanding is that any issue with how the lens/adapter is interacting with the sensor would manifest in the EVF.

I've also been working on the assumption that the zone of acceptable focus is usually 1/3 in front of the focal point, 2/3 behind, which seems flipped around here.

What's going on? Could IBIS be playing a role? I haven't attempted to recreate with a tripod because I'm travelling without my tripods, perhaps should try again without IBIS.

Click to expand...

Do you use the zooming tool for the pixel peaking focusing? If not, then the problem is solved.

Click to expand...

jhunna said:

Just curious is it standard to go this deep into problem solving an issue? I am new to the MF forum, and I think this level of depth is unique to this forum. Not a judgement, just an observation.

Click to expand...

jhunna said:

Just curious is it standard to go this deep into problem solving an issue? I am new to the MF forum, and I think this level of depth is unique to this forum. Not a judgement, just an observation.

Click to expand...

jhunna said:

Just curious is it standard to go this deep into problem solving an issue? I am new to the MF forum, and I think this level of depth is unique to this forum. Not a judgement, just an observation.

Click to expand...