Red filter in enlarger throwing off sharpness

Tom Kershaw · May 7, 2010

PE,

I may have missed something as I've not read through the entire thread but I never use a red filter in the path of the enlarger lens. Focus is checked before insertion of paper.

Tom

David A. Goldfarb · May 7, 2010

Posted wirelessly..

My current enlarger doesn't have a red filter, but when I've had one, I've used it to recheck alignment if I thought I bumped the easel and to position dodging and burning tools for multi-part exposures.

Photo Engineer · May 7, 2010

Tom Kershaw said:
PE,

I may have missed something as I've not read through the entire thread but I never use a red filter in the path of the enlarger lens. Focus is checked before insertion of paper.

Tom

Tom;

Read the OP again.

PE

RalphLambrecht · May 7, 2010

Photo Engineer said:
Tom;

Read the OP again.

PE

PE

This thread matured form the original question into questioning the necessity of placing a piece of paper under the focus finder. Now, Steve is trying to clarify if focus finder manufacturers have already assumed an average paper thickness, or if the bottom plane of the focus finder represents the paper surface, which I'm advocating.

Photo Engineer · May 7, 2010

RalphLambrecht said:
PE

This thread matured form the original question into questioning the necessity of placing a piece of paper under the focus finder. Now, Steve is trying to clarify if focus finder manufacturers have already assumed an average paper thickness, or if the bottom plane of the focus finder represents the paper surface, which I'm advocating.

Ralph;

Yes, I also commented on that in my post as well.

I have been told over and over again that there were two kinds of focus aid, but have never seen but one type which I have checked out several times. I have two and we had many at work. They all required that paper be placed under them before focusing.

I did not explicitly state the entire thing above, but there may be two types in spite of a lack of seeing the other variety.

Kind of like Bigfoot.

PE

RalphLambrecht · May 7, 2010

Photo Engineer said:
Ralph;

Yes, I also commented on that in my post as well.

I have been told over and over again that there were two kinds of focus aid, but have never seen but one type which I have checked out several times. I have two and we had many at work. They all required that paper be placed under them before focusing.

I did not explicitly state the entire thing above, but there may be two types in spite of a lack of seeing the other variety.

Kind of like Bigfoot.

PE

My Peak-I focus finder came with instructions which clearly show that no assumption about paper thickness is being made. The focus plane (paper surface) is at the bottom of the focus finder. I've never seen any other kind, and I'm glad about that. I hope they do not exist.

Photo Engineer · May 7, 2010

Interesting. None of the ones at work came with instructions as they were in use there for years. The box and instructions probably wore out in the days before Mees. I merely took advice on use and checked the advice.

My personal ones are quite old as well and were second hand gifts so I was in the same position.

I never would trust them on many of the easels I have due to the rail type paper holders which cause any object to be rather tippy or askew on the bare easel. This observation, empirical as it is, helped persuade me as to use. Of course, in my lifetime I have also seen focus aids with adjustable focal plane. You then calibrate them (with great difficulty) and have to continue to worry about keeping them calibrated. I never liked, nor used that type.

PE

RalphLambrecht · May 7, 2010

Photo Engineer said:
Interesting. None of the ones at work came with instructions as they were in use there for years...

The instructions of my Peak include a picture very similar to the one I included in post #41. An extract of the text is in post #60.

Photo Engineer · May 7, 2010

Well, it appears that neither of us have seen one that is used on the easel itself without paper.

I have a Burke and James unit, and one other that I have in storage. The B&J passes more light and as I get older I moved to it and put the other one away.

PE

Loren Sattler · May 7, 2010

Focus shift?

I never use the red filter, took it off the enlarger a long time ago. I also stopped using a sheet of paper under my grain magnifier long ago, could not see the difference one way vs. the other.

I have always been curious however, about focus shift. I focus wide open and typically print at 1-2 stops closed down from wide open. Occasionally, after working on one negative for a while, I will check the focus stopped down to see if the negative popped or the focus changed for other reasons. I usually end up refocusing then with the lens stopped down, so I don't change the exposure slightly from an aperture shift when resetting aperture. I know that better lenses yield less focus shift when stopped down, but how much shift is a little vs. at lot? Do all lenses regardless of quality have focus shift?

fschifano · May 8, 2010

I see this happening too. I always recheck the focus for each print. I know that in my case the negative isn't popping. It just doesn't get anywhere near hot enough with the dichro head on one enlarger. The heat absorbing glass on the my other, condenser enlarger does a good job of preventing the negative stage from getting too warm too. What does happen is that the enlarger head will creep down the column just a little bit if I forget to lock it in place.

Steve Smith · May 10, 2010

A reply from Tohkai

I have receiverd a reply from Mike Suzuki at Tohkai, manufacturer of the Peak focuser:

At first, it is not necessary for you to place a piece of paper under the focuser, but at the same time this is not compensated for in the desing. Because we conshider that the differnce from the thickness of a paper is the tolerance. In face, we have never heard from our customers about any inconvenience from that tolerance.

At the same time, we often hear that some users put a plate as thin as a paper under the focuser when using it. However we do not prepare such a plate formally, because every user has different papers from many companies, it means it depends on his condition.

I think the bit about the tolerance is interesting. What he is effectively saying is that although it is designed to be x in length, it could end up being x + or - the paper thickness as a manufacturing tolerance. This means that using a piece of paper would make some product better and others worse but equally not using a piece of paper would make some worse and some better depending upon which end of the tolerance band they were manufactured to.

The other manufacturers will also have the same tolerance issues.

I think then that the concensus of opinion is that these devices are designed such that the plane of focus is on the base and if you want to put a piece of paper under it you can but it doesn't really make any difference.

I think we need to concentrate our efforts where things actually do make a difference such as the flatness of the negative and the alignment of the negative carrier and lens carrier.

Steve.

Tom Kershaw · May 10, 2010

Steve Smith said:
I think we need to concentrate our efforts where things actually do make a difference such as the flatness of the negative and the alignment of the negative carrier and lens carrier.

Steve.

A good point, and in my experience different film stocks exhibit varying degrees of flatness in the negative carrier.

Tom

RalphLambrecht · May 10, 2010

Steve

Thanks for the effort. I'm glad it's official now.

Red filter in enlarger throwing off sharpness

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