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Photo Forum / Film Photography / Darkroom / February 2004First contact prints done. Problem with light uniformity.
I have finally done my first contact prints... and many questions arose from that. Much more than after the development of 1st film!! Here is the first one. The light coming from the enlarger is NOT constant all over the lighted area. I have noticed that after beeing suggested to pay attention to the visibility of the sprocket holes for reference. If in the center of the sheet are not visible they are at the borders. I am assuming that there is at least 1/2 or even 1 stop difference. Considering that I have an Durst M601 with Componon 50mm f2.8 is this normal? Corrective actions?? Ciao, Fabio BERETTA Lecco - Italy Fabio BERETTA <beretfab**NOSPAM**@tin.it> wrote in news:bRbWb.217746 $VW.8895216@news3.tin.it: > Considering that I have an Durst M601 with Componon 50mm f2.8 is this > normal? Corrective actions?? > > Ciao, > Fabio BERETTA > Lecco - Italy Light falloff at the edges. You need to use a smaller aperature, like f/8 or f/11. Bob Sounds to me like he needs to install the correct condensors/mixer for the lens... denny > Fabio BERETTA <beretfab**NOSPAM**@tin.it> wrote in news:bRbWb.217746 > $VW.8895216@news3.tin.it: [quoted text clipped - 10 lines] > > Bob or perhaps put in the correct mask in the carrier since the 50mm will not cover the entire area of the 6x6 glass -- darkroommike ---------- > Sounds to me like he needs to install the correct condensors/mixer for the > lens... [quoted text clipped - 13 lines] > > > > Bob > Sounds to me like he needs to install the correct condensors/mixer for the > lens... > denny yep... you sound like you've got two Sivocon 80's in it. Are both condensors identical? I just tried a 50mm lens with the two '80s and there's definite light fall off. With a Sivocon 50 and one '80 (the 35mm setup) it looks quite even, which I'd expect since I've never had to edge burn my prints. FYI, the '50 condensor has a lot more curviture to it than the '80. Nige. I have used f11! > Fabio BERETTA <beretfab**NOSPAM**@tin.it> wrote in news:bRbWb.217746 > $VW.8895216@news3.tin.it: [quoted text clipped - 10 lines] > > Bob I'm not familiar with the M601... Does it have a condenser head, or a light mixing box? Whichever it has, is the correct set for 35mm film/lens installed? If the correct set is installed for the lens you are using, did you have the 35mm negative carrier inserted during your white light exposure for the contact prints? While it is intuitive that the incorrect condenser or mixer box wiill cause light fall off problems, it is not as intuitive that leaving the correct negative carrier out of the light path will cause unevenness of the light - which it will... Other issues, such as the light bulb not being properly aligned, a wadded up paper or filter somewhere in the light path, dirty or hazy lens, etc., can be explored also... Good hunting... denny > I have finally done my first contact prints... and many questions arose > from that. Much more than after the development of 1st film!! [quoted text clipped - 3 lines] > The light coming from the enlarger is NOT constant all over the lighted > area. Lens was clean I bought the componon because I had proble with fungus with my previous lens. In the head there are: - light bulb - a mirror - two thick lenses simmetrically installed with the convex part in the middle - the 50mm lens attached to a flange I have tryied to adjust bulb height in order to maximize the light but it reaches the top of the head and cannot be adjusted more I let the negative carrier installed partly reducing the area with the moveable masks. > I'm not familiar with the M601... Does it have a condenser head, or a light > mixing box? Whichever it has, is the correct set for 35mm film/lens [quoted text clipped - 20 lines] >>The light coming from the enlarger is NOT constant all over the lighted >>area. > I have tryied to adjust bulb height in order to maximize the light but > it reaches the top of the head and cannot be adjusted more Is this the height of the bulb within the head, or the height of the head above the easel? The location of the bulb within the head is to maximize the evenness of the light, not the intensity.  SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. Height of the bulb within the head... that's probably the mistake!! Now is there any method to correctly estimate if evenness of the light has been reached? >>I have tryied to adjust bulb height in order to maximize the light but >>it reaches the top of the head and cannot be adjusted more [quoted text clipped - 4 lines] > The location of the bulb within the head is to maximize the evenness of > the light, not the intensity. > Height of the bulb within the head... that's probably the mistake!! > > Now is there any method to correctly estimate if evenness of the light > has been reached? The evenness of the contact sheet is a good indication... Seriously: o Eyeball it as best you can o Use a lightmeter with an incident disk attachment or an enlarging meter and see if reads the same in the corners as the center. Most light meters are not sufficiently sensitive and don't have enough resolution, though. o Check by installing a grade 5 polycontrast filter and making a neutral (18% - or so) grey exposure with no negative. See if is even enough to satisfy you. Tear off a corner and place it in the middle of the print to make the comparison. SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. Thanks. >>Height of the bulb within the head... that's probably the mistake!! >> [quoted text clipped - 16 lines] > if is even enough to satisfy you. Tear off a corner and place > it in the middle of the print to make the comparison. > I have finally done my first contact prints... and many questions arose > from that. Much more than after the development of 1st film!! [quoted text clipped - 14 lines] > Fabio BERETTA > Lecco - Italy Raise the enlarger head so that the light on the paper is bigger. This way you will only use the center of the light pattern and avoid the falloff near the corners. Just increase the exposure time to compensate. You should also use f8 or f11. SignatureRobert D Feinman robertdfeinman@netscape.net Landscapes, Cityscapes, Panoramas and Photoshop Tips http://robertdfeinman.com |
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