Friday, February 20, 2015

Film verses Digital



A comparison of fine grain black & white film and digital images.

Except for artistic reasons, when shooting film, most photographers are concerned about excess grain and try to eliminate it as much as possible.  Unfortunately, that cannot be achieved all the time.  It is an accepted fact of photographic life that faster films do display more grain than their slower counterparts.  Obviously, we have to match the films we choose to the lighting conditions under which we take photographs.

Grain is also very closely associated with sharpness and detail in a photograph.  A coarse grain film simply cannot show as much detail as a fine grain film.  Fine grain films are therefore inevitably sharper and for that reason more desirable.

The slowest black & white films on the market used to be Kodak Technical Pan, Agfapan APX 25, Efke KB 25 and Ilford Pan F.  The Kodak Agfa and Efke films had a standard rating of ISO 25, while the Ilford had a rating of ISO 50.  All three of them were outstanding examples of modern, fine grain films, and must be considered the best the market had to offer.

Kodak Technical Pan basically was a slow, high contrast film with extended red sensitivity, meant for copying of documents etc.  In the appropriate developers, the film would display extremely high contrast as is necessary for such work.  However, when developed in Kodak Technidol or similar developers, the film would display a continuous tonal range with near normal contrast.  If we go strictly by published specs, there is nothing comparable on the market.  Technical Pan had finer grain and a higher resolution than any other film readily available.  This should make it the undisputed leader in the fine grain film field.

Technical Pan could deliver negatives of incredible sharpness.  However, since the film was basically a very high contrast material, it did suffer from relatively high contrast, even when developed in Technidol.  When used in bright sunlight, the results were fairly contrasty, too much so for a lot of photographers. The film also had a low exposure latitude and required a very specific developing procedures to make it useful as a standard, pictorial film material.

While the performance potential of the film was unquestionably very high, it remained a special purpose film with considerable limitations.

The Ilford Pan F is certainly a tremendously capable film, but by virtue of its higher speed, it is not quite capable to deliver the performance of the Kodak Technical Pan or that of the Agfapan APX 25 and Efke KB 25.  The Ilford film therefore has to be considered to be on the bottom of this list.

As far as published specifications go, the Agfapan APX 25 and Efke KB25 are not quite as sharp and don’t have quite the fine grain of the Kodak Technical Pan.  On the other hand, the films easily allow adjustment of contrast by changes in exposure and development times.  In addition, they do not require special developers.  Any good black & white developer can do an outstanding job with these films.  One such developer is Agfa Rodinal.  Rodinal is not a particularly fine grain developer, but it displays a very high acutance, which yields extremely sharp negatives.  Agfapan APX 25 and Efke KB 25, developed in Rodinal, have proven to deliver negatives of exceptionally fine grain.  Enlargements of 15 times have proven to be virtually grainless, and even enlargements of 30 times are still quite acceptable.  Of course, this is also very much dependent on the quality of the camera equipment.

The question is often asked if APX 25 or Efke KB 25 couldn’t deliver even finer grain if a so called fine grain developer was used.  The answer is certainly “yes.”  But why?  If 15 or 20 times enlargements from these films, developed in Rodinal, show virtually no grain, why try to reduce grain size?  It wouldn’t make any visible difference.  However, the coarser grain structure of high acutance developers usually renders a greater apparent sharpness.  A finer grain developer therefore might have the effect of less apparent sharpness due to lower acutance.

Reduction of development times in Rodinal will lower the contrast of the negatives while an increase in development time will result in the opposite.  In addition, the film can quite successfully be pushed to a rating of 50 and still yield very good results.  The film can also be pull processed at a rating of 20 or 15, to yield even finer grain.  This will also result in a noticeable reduction of contrast.

It is this versatility which ultimately made the Agfapan APX 25 and Efke KB 25 more desirable films than Kodak Technical Pan.  Given the right lighting conditions, they are without question some of the best black & white films ever made.

 
This photograph shows approximately the entire negative area.
It was scanned from an enlargement which was carefully adjusted
during printing to render an exact 8X magnification.

 
This cropped section of the original negative was scanned
from an enlargement, adjusted during printing to be an
exact 16X enlargement

 
 A section of the same 16X enlargement, scanned from the original print.

 
This portion of the negative was scanned from a 35X enlargement.
The very fine eye lashes in the upper left corner have an approximate
Diameter of 0.007mm (0.00028 inch) on the negative which translates to a
resolution of over 140 lpm (lines per millimeter) on the enlargement
which means that the on-film resolution is even higher.

Unfortunately, the overwhelming popularity of digital photography has influenced the photography market to the extent that many films have been discontinued.  Of the fine grain black & white films, only the Ilford Pan F remains at the moment and therefore has to be considered one of the best currently available.

Of course this brings up the question if digital cameras are capable of delivering images of equal quality and the answer is; definitely, providing we are talking of camera equipment and especially lenses of equal quality.  As a matter of fact, given a sufficiently large sensor, especially full 35 mm frame sensors with sufficient resolution, the same lenses might deliver even higher quality images with a digital camera.

The limiting factor of maximum resolution on film besides grain size is the fact that light will scatter within the emulsion.  This definitely reduces overall resolution and it is the very reason why films will never be capable of delivering all the resolution, all the detail that a high quality lens is capable of.  In comparison, most digital sensors do not have this scatter effect, meaning that a less quality reduced image can be produced.  Of course the ability of the digital camera system to suppress noise and other image degrading phenomena are a factor also.

Following is a photograph taken with a digital camera that shows that comparisons to even the best 35 mm films present no problem.  I purposely chose the Leica Digilux 2 which has a modest resolution of only 5 megapixels.  However, it should be noted that compared to consumer cameras with similar resolution, the Leica Digilux 2 has a relatively large sensor that allows for larger individual pixels.  The result is a higher image quality, especially if the camera is used at lower exposure indices.  It is obvious that in spite of the relatively low resolution, the resulting images compare quite favorably with the above black & white images taken with exceptional camera equipment and exceptional film.

 
Image uncropped

   Image cropped from a 27 x 36 inch full frame image

The sharpness of the images shown is such, that some of the small detail is so fine that it wouldn’t show on an enlargement unless enlarged to approximately 16 x 20 inch.  This is for instance the case with the above black & white images.  On an 8x10 enlargement, the very fine lashes are invisible.

Technical Data
Black & White Images

Camera:                      Leica M3
Lens:                           50mm Dual Range Summicron f/2
Film:                            Agfapan APX 25
Light Source:               Broncolor Impact with 25” soft light reflector
Developer:                   Agfa Rodinal 1:100, 68ยบ F, 16 Minutes
Enlarger:                     Leitz Focomat V35 with Leitz Focotar, 40mm f/2.8 and color head module

Technical Data
Color Images

Camera                       Leica Digilux 2
Lens                            7-22.5 (28 – 90 equiv.) Leica DC Vario-Summicron f/2 – 2.4
Exposure Index            ISO 100
Light Source                Speedotron Brown Line D402 and D802 both at 200 ws with umbrella and reflector fill

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2 comments:

  1. I am amazed how well the Digilux 2 looks on these examples. After all, it is a relatively old digital camera. I would like to see the results of one of the current Leica cameras.

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  2. Nothing I couldn't do with a Holga or Diana camera. Seriously, these results are quite impressive

    ReplyDelete