ewan70
newbie
Reged: 24/04/2008
Posts: 5
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I am using a Kaiser VP6005 b/w enlarger with a meopta anaret s 50mm lense. My problem is that it is not giving an even illumination across the easel and therefore affecting my prints at the edges, which are lighter. i am a relative novice but have a basic grasp of darkroom practise.
i have the analyser pro from rh designs and have been using the densitometer on it to measure the differences from centre to edge on film base+fog through the enlarger that i know has a uniform density and it is from 0.00 in the centre up to about 0.3/0.4 at the edges. that is about 3 Zones in zone system terms and cant be right.
i have checked everything possible, adjusted the lamp, tried different heights, with and without the lense but get nowhere.
i do not have the experience to be able to make an informed guess at the cause other than bad choice of enlarger and lense (the kaiser advertising bumph states how much work has gone into making the lighting even). i was in contact with the importers but they seem to have disappeared.
for snapshot prints its fine(contact prints are dark in the middle lighter at the edges) but if i want to progress into more serious photography it will be a major prob because i will never get accurate readings or tone reproduction.
what is the usual amount of fall-off that can be tolerated from enlargers and does it get smaller for better ones?
any advice would help, i have just bought a schneider componon lense which may or may not solve it but will at least be a good investment(i hope.
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ewan70
newbie
Reged: 24/04/2008
Posts: 5
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i have just sorted this prob out, so no point racking brain cells, thanks.
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taxor
Reged: 09/07/2004
Posts: 556
Loc: Lancaster, UK
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Glad you got it sorted. What was the prob? Anyway, one would normally expect a small amount of falloff from a condensor type enlarger. Is this the type of B+W enlarger you have? To be honest, it sounds OK to me. My Durst AC707 has a condenser head and at full aperture (using a Shneider Componon S - one of the best lenses there is) typically reads around 0.3~0.4 difference between the centre and corners, as measured with an RH designs Zonemaster 2. This improves as one stops the aperture down, which is what I'd expect in your case. Even when I used a colour enlarger (with a diffuse light source) there was a slight amount of falloff. Next time you make a print, just burn the edges in a little. I've rarely made a (big) print that didn't require some printing in at the edges. Hope this helps, Taxor.
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"I wanna hold your gland". Lemming & McCartney
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ewan70
newbie
Reged: 24/04/2008
Posts: 5
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i think the biggest problem was just that i had no idea whether it was normal and i was just digging too deep.
but anyway i slightly improved it by cropping a bit tighter and also putting a bit of diffuse material under the condensor, which i know makes it a kind of DIY diffuse enlarger but having seen the results i prefer the softer contrast with the material in, so i will find s'thing suitable to use permanently.
i've never been keen on high contrast anyway and wish i had bought a diffuse enlarger but thats life and my own fault.
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 4485
Loc: Really Here In Name Only
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Quote:
Anyway, one would normally expect a small amount of falloff from a condensor type enlarger.
It's not a bad characteristic, when it tends to counter the tendency to vignetting in the camera, which makes the negs thinner towards the corners and therefore requiring less light to get to the corners of the paper during enlargement.
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taxor
Reged: 09/07/2004
Posts: 556
Loc: Lancaster, UK
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I think I read somewhere that the Kaiser VP6005 was a hybrid diffuse/condensor light source, so it may be that your putting a piece of diffuse material in the lightpath is actually restoring it to its original spec! Beejaybee is also right about lenses to some degree causing a slight vignetting of the image. Generally speaking, the best lenses (i.e. better constructed, more elements etc) reduce vignetting and other optical maladies to a minimum. This makes them more expensive. This also applies to enlarging lenses. If you're going no bigger than 10x8 prints, a Meopta Anaret lens will do the job well, especially if you stop the lens down. Trouble is, if you're going bigger than that, you'll need all the light you can get to avoid excessively long exposure times. Opening up the aperture will show the vignetting again. This is when a good 6 element lens comes into its own. This is also why it is always best to buy the very best lens you can afford. Luckily, at the moment, there are lots of bargains to be had with enlarging lenses.
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"I wanna hold your gland". Lemming & McCartney
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Terrywoodenpic
A whiff of silicon...
Reged: 21/01/2006
Posts: 281
Loc: Saddleworth UK
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I do not know about this particular enlarger, but most condenser enlargers need the light source adjusted so that it is focused by the condensers through the lens. Properly adjusted it removes both uneven illumination and vignetting.
I have used several dozen enlargers from the 1940's to the late 80's and they all but one had this feature. and that was factory set.
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63 happy photo years from amateur to professional and back to amateur
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 4485
Loc: Really Here In Name Only
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Quote:
but most condenser enlargers need the light source adjusted so that it is focused by the condensers through the lens.
It has to be, if you change the bulb (and they do blow) the filament will be in a slightly different place, hence the need for adjustment.
Quote:
Properly adjusted it removes both uneven illumination and vignetting.
Removes?
If you'd used the word "minimizes" I would agree unconditionally.
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taxor
Reged: 09/07/2004
Posts: 556
Loc: Lancaster, UK
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There's not much adjustment you can make on some enlargers. I'm talking about the type that use a 'reflex' system a la Durst etc. You can only adjust the height and rotation of the bulb (I'm not sure if you can even do that on colour heads of the same design!), all other parts of the optical train being fixed. Looking at the OP's enlarger, it seems to be of this type.
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"I wanna hold your gland". Lemming & McCartney
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ewan70
newbie
Reged: 24/04/2008
Posts: 5
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out of interest ,this is the reply i had from the horses mouth, kaisers anyway.
it would be pretty helpful if thet put info like this on their advertising, it wouldnt be as glamorous or glitzy but would at least be honest.
quote..'The light distribution depends also on the quality of the opal lamp
itself. There are small differences in the inner coating of that bulb.
That can cause sometimes an uneven light distribution. Some very critical
users are testing bulbs of different manufacturer runs.
A better light distribution is given by a halogen construction. The
mulitgrade head and the color head contains that construction. It will
give a smoother light and a better distribution.
The disadvantage is a reduced brightness because of the integrated
diffusor plate.
I know, that is not the solution for your customer, but a head with an
opal bulb can never
give an absolutly even light distribution.' end quote.
thankyou for all your replies, i have learnt alot from this .
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mediaman
I can blubber for hours
Reged: 28/07/2008
Posts: 416
Loc: edinburgh
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use a lens covering a larger format....75 or 80mm should fix the problem of uneven light coverage. you will still get at least 10x12 prints. assuming you are enlarging 35mm negs.
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Kenny.
The tears of laughter were running down my legs.
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