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  1. #1

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    How to adjust a grain focuser?

    I picked up a second grain focuser (by Thomas Instrument) recently and compared it to my old Accura model that I have used for years. See photo. I discovered they do not agree, the Thomas Instrument is more accurate when enlarging at full aperture (2-1/4 sq negative at 11 x 14 print size, Nikor lens at f5.6). The print is noticeably sharper.

    Are these focusers adjustable? How?

    Thanks in advance.
    Attached Thumbnails Attached Thumbnails IMG_0840.jpg  

  2. #2
    Newt_on_Swings's Avatar
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    the one on the right is not adjustable, the one on the left should be be adjustable. easiest way is to load up a negative into the enlarger, make it unfocused, and put your eye up to the reticle, inside you should be able to see a line, or box, adjust your eyepice by rotating it until that line or box is sharp. Then you can focus your image as normal, but use an area that close to the line, or place the grain inside the box for best results. Move the grain finders around the image as well, and also check corners.

  3. #3

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    The previous post answers your question almost completely.

    I would just like to add something perhaps very subjective, but nevertheless from years of experience: when I place the grain finder (Peak in my case) in the middle of the image it is easy to see everything, but in the final print the grain in the corners may not always be as sharp as in the middle of the image. When I place the grain finder in a corner it is a little harder to see the grain, but in the final print both corners and the middle of the image have perfectly sharp grain.

    So, I always place the grain finder in a corner.

    I think the reasons for this are in the lenses. With my Focomats 1C and 2C came first-version lenses. I could only get the grain sharp doing what is described before. Later on I got later-version lenses (Focotar-2 50mm and 100mm) and with these it seems easier to almost always get sharp grain from corner to corner, even when not stopping down.

  4. #4

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    I don't know about the adjustability of either, but an option to keep in mind is that you can raise the focus tool. If this is the right direction to "correct" the tool, just write the needed correction on the bottom. Back at a time when I was crudely prototyping equipment, I often used pads of Post-it notes for shims; this would be a convenient way to raise a focus tool by some arbitrary amount.

  5. #5
    Seele's Avatar
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    I always use mine with the lens set at working aperture, it should take care of the possibility of focus-shift. I mainly use Paterson's but also use a Bausch & Lomb parallax focusser.

  6. #6

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    What brought this to light is I recently started using some Fomatone MG warm tone paper which is a very slow chlorobromide paper. To reduce exposure times to under 20 seconds I have made a number of 5 x 7 prints at full aperture (f5.6 for med format and F4.0 for 35mm). I noticed the enlargements have not been as sharp as I am accustomed to, so I tried the Thomas Instrument unit on a bigger enlargement. The test print was significantly sharper than a test print made wide open with my old (Accura) grain focuser. In the past I have rarely made prints wide open, usually two to three stops closed from wide open. Obviously I have gotten by because of the depth of field provided with these narrower apertures.

    I am going to need to find a smaller grain focuser since the Thomas Instruments unit is physically too large to work with 5 x 7 prints. It is too tall to fit under the lens stage.

    Thanks to all for the responses.

    Looking at the Peak units, there are three models (1,2, and 3) available ranging in price from about $60. to $350. Any comments on the merits of the three models?

  7. #7
    Newt_on_Swings's Avatar
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    I use the peak 1, its my go to grain focuser. It has the largest mirror of the three, and the adjustable angle eyepiece lets me get an image from any corner of the print easily. It is built very well, and the stand looks as if it was machined out of a solid block of metal. Blue filter makes focusing easier but thats a whole other bag of worms. (You can search about it, and its debated)

    They dont come up for sale used that often, i mostly see the smaller 2 or 3 pop up, i guess its a testament to how much people like them.

    You may be able to get by with a magnifying pair of reading glasses, or a handheld magnifier at an enlargement of only 5x7. Its probably the cheapest way.


    Sent from my iPhone using Tapatalk

  8. #8

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    Peak grain finders are great. One just sees much more easily with them. I don't have the cheapest model, but do have the middle and the top model. Both are better than anything else I ever used and the top model is still worth the extra cost. Sorry, but I am always confused about their model numbers. I think you can find the most expensive model for less than $130. A tip: the mirror is two sided, you can turn it around if one side is scratched !

    I would reconsider trying to reduce your enlarging times. I print up to 20X24 on fiber papers and exposure times of 60 seconds and more are very normal. All my lights go off while exposing, I think that is a must. But stopping down the enlarging lenses is essential, with all respect.

  9. #9

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    BTW when focusing, be sure to use a piece of the same paper under your focuser.
    Height makes a difference.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  10. #10

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    Quote Originally Posted by paul ron View Post
    BTW when focusing, be sure to use a piece of the same paper under your focuser.
    Height makes a difference.
    I have seen a lot of posts backed by experiments carried out by the posters that have concluded that this is a myth.It is to do with the DoF which gives a range of focus that well exceeds the thickness of the paper

    OP, do a search of posts on APUG and then decide for yourself

    pentaxuser

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