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you need to be aware that a polarising filter is not the same as a neutral density(ND) filter. An ND filter will stop as much light as it is calibrated for across everything in the image. A polarising filter works differently and will stop differing amounts of light depending on the angle of...

I said that UV light is not good. I also said that sunlight has UV. I also said keep chemicals out of light when stored. Thats all. But you claimed that enlargers don't give out UV. Why? Oviously if developer is stored its not going to get exposure from enlarger. But no you wanted to argue the...

At higher altitudes the sky is a much deeper blue than at lower altitudes. And the air is colder at altitude and contains much less water vapour if any. The air is very dry at 12000ft. So I figure there would be much less need to use a grad compared to lower altitudes such as coastal shots over...

I think you missed the point of the link I provided or didn't read it. Its the temp of the filament which makes the difference and domestic tungsten/halogen bulbs are not much hotter than a standard light bulb. BUT projection bulbs as found in enlargers are much hotter and do emit more UV...

Usually it doesn't stay in the glass long enough to notice and I thought I was just seeing things becasue I'd had too much to drink.

see last section "Ultaviolet from Halogen Lamps" of following but the first section gives some background. Dead Link Removed

paper can only ever be as bright as it naturally is (unless it has added fluorescent which some papers do). Most papers are plenty bright enough. It will be something about your printing which is wrong. Either your filtration is wrong and/or you are over printing and/or your development is not...

I repeat, quality enlargers using tungsten bulbs have built in UV filters. Its no wonder you can't expose when using a paper which requires UV light. You would need to remove the UV filter or not use an enlarger and use bare bulb. But you are confirming what I said. A no light or low light...

They are a German company with some regional offices in Europe. Not sure about North America/Canada. Try emailing this address and ask for list of suppliers in your region. I'm guessing they they must have some dealers on your side of the pond as they say they are in 100 countries or have...

topic has been running for nearly six years and you're all still disucssing what a K factor really means. LOL.

tungsten bulbs give out UV which is why good enlargers using tungsten bulbs have built in UV filters. I thought UV is quite damaging. And sunlight gives out a lot of UV. Best keep checmicals out of light when stored.

another major thing to consider in keeping life of stock solutions is ambient temperature. If you have a dedicated darkroom then consider installing a fridge and keep stock solutions in it. The cold temp will make it keep for a lot longer. Storing chemicals where they will get warm will reduce...

No I don't think so. The exception is that glass is easier to clean than the plastic (PET) compression bottles and being clear you can see if there is any staining/residue left in glass bottles. And you can scrub inside bottles with a suitable flexible brush which isn't so easy with a black PET...

doesn't matter whether the storage container is clear plastic, black plastic, clear glass or brown glass providing you store them in a closed cupboard with no light in it. The chemicals are oblivious to what colour the container is. Light has a bad effect on chemicals over time. You just need...

The next and very big hurdle to overcome is being able to put the enlarger head at a height which won't cause the foot of the column to protude into the intended image size. This may require turning head horizontally but I would like to avoid that if at all possible. More calcs required and...

I thought so but that is becasue the recess is made in the knowledge that it will be using a narrower lens than the one I'm looking at using which is fatter. OK I have done some digging/unpacking and have managed to take some measurements and check lens measurements/design/specification...

anything you dilute with water will oxidize with time. Stock solution quite slowly if you keep air and light from it. But working strength developer very quickly. Off the shelf developers which come as syrup (which is usually glycol or TEA based solutions) keep a very long time. Products such...

MSDS for Tetenal STABINAL says it contains Polyethylene glycol octylphenyl ether potassium thiocyanate maybe some research on how to make those or just stock up on STABINAL which costs £7.32 for 20m2 of black and white paper protection. doesn't say it can be used for film but maybe it can...

I do have a photocopy of the manual which came with my enlarger and some durst brochures and also a couple of L1200 pdfs. None of them show a recessed board with an M50 thread size. I don't know if such a thing exists. I also don't know if the lens would work with the LAPLA 50 flat lens board. I...

but that is not an M50 X 0.75 thread size. I think that one is an M39 thread size. Most 50mm and 35mm lenses use an M39 thread size. The particular lens I'm thinking of has an M50 thread size but I think it will require it to be recessed.

Has anyone ever used a 40mm lens with an M50 X 0.75 thread size on a durst L1200 and which lens panel did you use? I have a LAPLA 50 lens panel which the lens will fit but I don't know if I will be able to focus that without a recessed lens panel. Enlarger is packed away at the moment pending...

This is an often made point. Technically if you make one image with say 100mm lens and and another image with 50mm lens from same position of exact same subject and then compare the same area of two prints they will look identical. However, if you move closer with the 50mm lens to get the same...

The standard lens focal length for each film format is approximately the diagonal of the film format. And note I said approximately. It has nothing to do with the eye or they eyes focal length or the eyes filed of view. Using the diagonal of the film format as the standard focal length will...

1 stop more exposure than you were using with 100 ISO. film ISO speeds are relative to one another in terms of exposure. Each doubling or halving of the ISO speed requires a 1 stop exposure adjustment. Halving ISO speed requires 1 stop more exposure. Doubling ISO speed requires 1 stop less...

he specifically said a 48in wide object size to fill a 4x5in image size. There is only one distance for his specific lens focal length hence all the calcs for it being given. And he said appoximate values are good enough as he can fine tune once he gets close to right focus.

if your grads are ND then I would take a reading of anything without the grad and then meter the same point through the grad at top to find the difference. i.e. how much the grad reduces the exposure at the top and then meter the same point through grad and bottom end of grad area. Then you know...

object angle is 75.818. Since I've been using this qioptiq software which is quite a lot of years, I've forgotten all the lens formula I used to know. Which only goes to show that automation and access to software makes you lazy.

for most lens calcs there is a free android app written by one of Rodenstocks lens designers. It will give you all the numbers you want for your lens extension and lens to subject distance. It can never be 100% accurate for what you are doing but you won't find anything more accurate unless you...

5x4 image area isn't 5 inches wide. I'll assume its 12cm wide or 4.72 inches which gives us a magnification of 4.72/48 = -0.0983X then using focal length of 147.7mm we get an object to film plane distance of 1812.01mm(71.34in) lens extension will be 162.22mm(6.39in) and lens to object will be...

Filter factors are either expressed as for example 2X where 2 means twice as much exposure. This would be calculated as 1/(60/2) = 1/30. You can open aperture instead to achieve the same. Or filter factor is expressed in log10 values with each .1 being a third of a stop. So instead of 2X it...