Quote Originally Posted by noseoil
Donald, is the 1,000w bulb a conventional long-tube type, similar to a work lamp bulb? Did you design a parabolic refelctor, or were you able to adapt a readily available refelector to suit your needs? How did you deal with the heat output from this light source? Seems like you could fry an egg on the housing after a while with 1,000 watts flowing through the lamp.

How does the "point light" source differ from a conventional condenser enlarger? I have no background in physics, so a layman's explanation would be helpful.

Finally, could you take an image and enlarge it using the various methods at your disposal by way of an example? I still use an old D5-XL with a color head, but would be interested in anything which makes for a sharper print. Thanks, tim
Hi Tim,

Thanks for your response. You pose very good questions. I will try to answer your questions in the order that you posed them

No, This is a bipin type lamp and not a long tube double ended lamp. The reflector design is not parabolic since a parabola would tend to do the opposite of what is needed in this case. I was not able to utilize an existing reflector. The reflector that I ended up using is a shape that incorporates both convex and concave forms in the design. I designed the shape and then built the reflector.

To deal with the heat, I utilize a blower to cool the lamp house. I have measured the lamphouse internal temperatures using a highly accurate digital thermometer. The maximum temperatures that I have recorded have been 135 degrees after one minute and thirty seconds of exposure time. This is a very unlikely exposure scenario since a typical print exposure would be twenty seconds at F16 for a 16X20 print from a 4X5 negative. Typical 8X10 enlargemens from a 4X5 negative are 8 seconds at F22. Needless to say, this is very fast when compared to the 250 watt lamp that I had used to this point.

By contrast without using a blower, I have cracked and melted glass with this lamp since it operates at 500 degrees celcius.

I will now try to explain the difference that a point light source provides. I will illustrate this by saying that the smaller the source of light in relation to the object that it is lighting, the higher the contrast between shadow and highlight of the lit object. To illustrate, if we take the sun in relation to the earth on a clear sunlit day, we notice that we have very distinctly formed shadows. However conversely if we examine a day when we have a cloud cover, the shadows are not well formed or distinct. The reason is that the clouds have had the effect of transforming the relative small light source (the sun) into a larger light source (the backlit clouds). A point light source more closely replicates the effect of the sun in the example above. All other light sources are some form of the cloud covered sky in vary degrees of thickness of cloud cover. The most diffuse would be the cold light source or the diffusion light source used in varible contrast enlargers or color enlargers. The less diffuse would be the condenser enlarger using a frosted lamp such as the Thorn lamp that had been commonly used in the Durst enlarger that I have.

All point light sources would be used with condenser enlargers since the desired effect is obtained by using a small light source with an optic system that serves to collimate and focus the light at the nodal point of the enlarging lens.

In regards to providing images, I am sorry that I don't own a digital camera and my scanner is on the blitz right now. I will say that images would probably not provide help to you since each manufactures lamp house would entail different and specific design criteria.

I hope that this answers your questions. If I have failed to explain myself completely please feel free to ask followup questions.