Another 4x5 newbie with focus problems

[Gimenosaiz]

Hello!

I've read this thread:
(there was a url link here which no longer exists)

... but I decided to open a new one because I've a different camera and our problems could be different as well.

I own a Pacemaker Speed Graphic with Graflok back. I mainly intended using the camera with an Aero Ektar 178/2.5.
I focus with the ground glass. By the way, thickness measures:
- Ground glass: 1'54mm
- Fresnel: 1,78mm -> Between the gg and the lens

I've spent a lot of film just to achive four or five focused pictures (two of them in the gallery). So, I think I've a problem.
This two photographs should have the focus on the red circle ... but, as you can see the focus is on the blue one.

1.


2.



What do you think?

Thank you !!

Best regards
Antonio

 

[removed account4]

hi antonio

first of all, nice photographs !
are you focusing wth the lens wide open or are you
stopping down a little bit to focus ?
i can't really speak for your problem is it is a hardware-issue ( strange / obscure equipment related issue )
but if it is a learning curve / focusing with a fast lens issue i have a trick for you
( well, its not really a trick, it was included in the instructions for a portrait veritar i have )
wollensak used to suggest to stop the lens down a stop or stop+1/2 to make it easier to focus
i have done that with other fast lenses, and it seems to help a little bit. with fast lenses, ( 4x5 )
the focus is such a "sliver" ( narrow ) that it it isn't easy to see what is in focus ...
maybe stopping down a little will help ?

looking forward to seeing more beautiful portraits !

good luck !
john

 

[gzinsel]

It could be that your film plane is at a difference distance than the GG. Have you measured This with calipers?

 

[Neal]

Dear Antonio,

It is also possible you have one or the other of the ground glass and freznel turned the wrong way. You should visit Graflex.org.

Good luck,

Neal Wydra

 

[shutterfinger]

The correct order of assembly is Fresnel with the ribbed side facing the rear of the camera then the ground glass with the ground side facing the fresnel/camera lens.
Is the Fresnel the factory one?

 

[Sirius Glass]

Dear Antonio,

It is also possible you have one or the other of the ground glass and freznel turned the wrong way. You should visit Graflex.org.

Good luck,

Neal Wydra

The correct order of assembly is Fresnel with the ribbed side facing the rear of the camera then the ground glass with the ground side facing the fresnel/camera lens.
Is the Fresnel the factory one?

Both of these are important. Use www.graflex.org for the archived articles and http://www.graflex.org/helpboard/ for the forum.

 

[couldabin]

Hi Antonio,

If the actual point of focus is further away than the point on the ground glass, the ground glass is too far from the lens (or, more precisely, further from the lens than the film). If the geometry of that camera assumes the ground glass is on the lens side but is installed the opposite way, that would create this effect.

duane

Hello!

I
This two photographs should have the focus on the red circle ... but, as you can see the focus is on the blue one.

 

[Dan Fromm]

Couldabin, Pacemaker Graphics delivered with fresnel lenses were designed to have the fresnel between the lens and the GG. The likely but not absolutely certain problem is that the GG is in backwards, with the ground (matte) side facing the photographer, not facing the lens as it should be. This is easy to check for.

Film holders are pretty well standardized and were/are industrial products made fairly well. Every time a question like this one comes up people suggest that the film holder is not to specification. I don't recall an instance that didn't involve an early MPP camera -- these beasties required non-standard film holders -- where a film holder that didn't match the specifications was the problem.

 

[ic-racer]

If the film focuses behind your GG image (as in your example) the film is too close to the lens. The film either is buckling in the film holder or the ground glass needs to be moved closer to the lens.

You can use the thin lens equation to see how far off you are. Without doing the math it looks like about 0.3mm to just less than 1 mm (assuming 150mm lens).

 

[Gimenosaiz]

Hello, everybody.
Sorry for the delay. I've got problems with my internet connection.

hi antonio

first of all, nice photographs !
are you focusing wth the lens wide open or are you
stopping down a little bit to focus ?
i can't really speak for your problem is it is a hardware-issue ( strange / obscure equipment related issue )
but if it is a learning curve / focusing with a fast lens issue i have a trick for you
( well, its not really a trick, it was included in the instructions for a portrait veritar i have )
wollensak used to suggest to stop the lens down a stop or stop+1/2 to make it easier to focus
i have done that with other fast lenses, and it seems to help a little bit. with fast lenses, ( 4x5 )
the focus is such a "sliver" ( narrow ) that it it isn't easy to see what is in focus ...
maybe stopping down a little will help ?

looking forward to seeing more beautiful portraits !

good luck !
john

Hello, John.

Thank you for your kind words.
I've done what you suggested ... But, no way.

Thank you, regards.
Antonio

It could be that your film plane is at a difference distance than the GG. Have you measured This with calipers?

Hello. Maybe, I've to measured this ...
Thank you !
Regards.

Dear Antonio,

It is also possible you have one or the other of the ground glass and freznel turned the wrong way. You should visit Graflex.org.

Good luck,

Neal Wydra

Dear Neal.
I think this could be the most probable cause … I’m not sure how to check it. Both sides are so similar! I'll check it ;-)
Thank you !

The correct order of assembly is Fresnel with the ribbed side facing the rear of the camera then the ground glass with the ground side facing the fresnel/camera lens.
Is the Fresnel the factory one?

Hello!
I'm not sure if the fresnel is the factory one. I guess is not.

Thank you!

Hi Antonio,

If the actual point of focus is further away than the point on the ground glass, the ground glass is too far from the lens (or, more precisely, further from the lens than the film). If the geometry of that camera assumes the ground glass is on the lens side but is installed the opposite way, that would create this effect.

duane

Couldabin, Pacemaker Graphics delivered with fresnel lenses were designed to have the fresnel between the lens and the GG. The likely but not absolutely certain problem is that the GG is in backwards, with the ground (matte) side facing the photographer, not facing the lens as it should be. This is easy to check for.

Film holders are pretty well standardized and were/are industrial products made fairly well. Every time a question like this one comes up people suggest that the film holder is not to specification. I don't recall an instance that didn't involve an early MPP camera -- these beasties required non-standard film holders -- where a film holder that didn't match the specifications was the problem.

Hello!
Couldabin, as Dan has said, the fresnel of my back is between the lens and the GG.
Dan, I’ve to check if the GG is backwards …
Thank you!!!

If the film focuses behind your GG image (as in your example) the film is too close to the lens. The film either is buckling in the film holder or the ground glass needs to be moved closer to the lens.

You can use the thin lens equation to see how far off you are. Without doing the math it looks like about 0.3mm to just less than 1 mm (assuming 150mm lens).

Hello!
I’ll look for that equation.
“the ground glass needs to be moved closer to the lens” -> What happened if the GG were backwards?
Thank you!!
Regards

 

[shutterfinger]

Run the back side/edge of a finger nail across the outside surface of both the ground glass and fresnel. They should be smooth, any roughness is a reversed panel.
The back is the same on a Top Rangefinder and Side/no Rangefinder model.
http://www.southbristolviews.com/pics/Graphic/manual-pdf/servicemanual.pdf
A factory fresnel has very fine grooves.

 

[removed account4]

Hello, everybody.
Sorry for the delay. I've got problems with my internet connection.




Hello, John.

Thank you for your kind words.
I've done what you suggested ... But, no way.

Thank you, regards.
Antonio

bummer, sorry my suggestion was no help ..

have you tried your camera with a different lens ....
( even a 150 or 135mm enlarging lens would work if you didn't have another "large format" lens handy )
... and had the same difficulty focusing ?

using a different lens would rule-out "camera issues" if the camera works as designed without issue ...

i have a few lenses that are impossible to focus ...
EVEN if i use them as an enlarging lenses with a grain focuser, they are not easy to focus at all ...

good luck !
john

 

[couldabin]

Reversing the orientation of the GG will move the apparent focus distance by the thickness of the GG -- closer or further, depending on its initial orientation.

What happened if the GG were backwards?

 

[Gimenosaiz]

Hello!
I reversed the ground glass ... and the problem seems to be solved !

Violeta helped me to do the test ;-)


1.

Graflex_Fo400_Hc_58_133 by Antonio Test, en Flickr

2. I inserted the film incorrectly in this one:

Graflex_Fo400_Hc_58_129 by Antonio Test, en Flickr

¡Abrazos!
Antonio

 

[Sirius Glass]

Great now you got your money's worth from APUG.