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Monday, 27 February 2012

Newton's rings.


This effect can happen when using medium format and larger negative carriers as they use glass to keep the negative flat. Most carriers today use a frosted piece of glass above the negative known as anti Newton glass. 
The rings occur in the areas where two clear smooth flat pieces of glass lie next to each other but do not quite touch. The interference happens because the light rays are refracted, this produces irregular shaped dark rings in the projected image. This will happen more readily if any of the surfaces are wet. You can get round this by using a paper mask with the negative in the carrier. This will block out the light in the places where there is a gap between the glass surfaces. You will need to check the projected image to see if they are still visible.

Saturday, 25 February 2012

Focusing. Soft prints why!



Ilford FP4+, Iso 125, developed in ID11
Printed on Ilford paper
There are reasons for your photographs to be out of focus. If we assume that the negative was sharp when it was exposed, it could be if you are using a glassless negative carrier that the negative may have popped and requires refocusing. Another cause is vibration, you need to make sure that you are not knocking the enlarger when you are exposing. If the enlarger is mounted on an uneven surface or rickety table this will not help nor will living near a main road with lots of heavy traffic.
If when looking at the photograph it looks  blurred, it has not been focused properly. You can cure this by using a focusing negative. To make one you need a negative of no value as you will have to scratch the emulsion in several places. It is simply a case of placing this negative in the enlarger and focusing until the scratches are razor sharp. Alternatively you can use a special focuser.

Wednesday, 22 February 2012

FP4+ developed in PMK Pyro method update


Zero camera, FP4+ developed
in PMK Pyro
The first permanent change is to go from two inversions every twenty seconds to one every fifteen seconds which is a reduction of two per minute. When I did this I wasn't sure if this would make the density of the negative less, as it turns out it has increased it, making for better toned prints. My conclusion is by decreasing the time between each inversion the developer in contact with the film surface is fresher for longer hence the increase in density. 

Zero Camera  FP4+ developed in PMK Pyro
Phelham bridge road Lincoln

I have also used an after-bath  (only with 120 FP4+) which does change the colour of the film base and seems to make them easier to print and at a softer grade. It has been suggested that the bath can reduce the sharpness of the negatives. Is this reduction noticeable? That's an answer you will have to find for yourselves as  I have only been using it so far with the film that's been exposed with the Zero pinhole camera, which is not known for it's ultra-sharp negative production. I will not be introducing it across the range of other makes of film I develop in PMK. I'm happy with the fine toned negatives it produces and see no reason to add the bath. 

Zero Camera FP4+ developed in PMK Pyro
Those of us who like to go against the mainstream will use it for creative or pictorial purposes but you need to be sure that the grain is sharp across the negative, it may add that extra something you are looking for to the final photograph.







Related posts:

PMK Pyro after-bath
PMK Pyro developer part B
PMK Pyro working solution

Monday, 20 February 2012

Deliberate distortion.

The enlarger is not there just to correct distortion but to add it as a compositional tool, in some cases to comic effect. The most obvious way of producing this is to bend the paper by clamping it between two blocks in a convex or concave shape. Double curves are possible. Remember the effect  aperture has on the depth of field and allow for it by using a larger F number to compensate and don't lose sight of the fact you will need to use dodgers to adjust the relative exposure.
This is Johnny from Fifth gear doing his piece to camera
about the re-launch of the Larda 4x4.

Agfa APX, iso 100, developed in PMK Pyro,
printed on Ilford paper 

Wednesday, 15 February 2012

Schaimpflug's rule.


This is the rule on tilting the easel and carries on from my last post.  The most accurate way of correcting distortion is to use Scheimpflug's principle: This states that you should tilt the negative as well as the baseboard and that they need to be canted over in opposite directions to each other. Additionally the incline should be such that the plane of the negative and the plane of the baseboard should meet in the plane of the aperture to give maximum sharpness over the whole image. 

You will find that the more expensive enlargers allow the plane of the negative to be tilted, add a tilting easel to the mix and the results produced can be remarkable.

Related posts:

Tilting the easel.

Saturday, 11 February 2012

Tilting the easel


Is mainly used for correcting those converging verticals in pictures of buildings. The reason you get sloping upright lines is because the camera has not been held vertical to the view.  View cameras (large format) are the only cameras that can keep the film plane vertical and look slightly upwards at the same time with out this distortion. You can buy a shift lens which has the same ability or do it in Photoshop.

When enlarging you negative you can correct this by using a tiling easel.  Simply lift the easel by the appropriate amount and rest it on a block. Remember that you need to lift the easel on the side that has the converging lines. When doing this you should set the smallest possible aperture providing the greatest depth of field. When making the enlargement, part of the picture may be lost, it is just a case of cropping the picture to make it square. After processing the exposure may be different between the top and bottom this can be corrected by dodging to even up the overall exposure.

Related posts:

Scheimpflug's rule.

Sunday, 5 February 2012

Mirror -image reversal


This is where the film is placed in the negative carrier with the emulsion side upper most obtaining a left right inversion, a mirror image. Negatives suited to this treatment cannot have any writing in them otherwise it gives the game away.

Which one of these images has been reversed?