To be sharp or not, how is the question.

Fg 1.
Film FP4+ developed in ID11 printed
on Ilford MG RC gloss.

A subject that is talked about by all photographers. No matter how you like to label it DOF or boken I am surprised that depth of field can be expressed by some in the terms of good and bad. Surely it is subjective and down to the person who has composed the picture.

So what is depth of field and how does it work?

Depth of field relates to the area of the image that is sharp. So the subject  you focus on in the view finder will be in the middle of the sharpness. How much this extends in front of or behind it, is dictated by the aperture you use. Small F number (large opening) very shallow, large F number (small opening) very wide. The other factor to have a bearing is the focal length of the lens used.  For example, with a wide angle 28 mm lens you would not require the focus to be exact because the depth of field would be quite considerable in front of and behind the point of focus even at small f numbers (large apertures). But with a Telephoto lens of 200 mm the point of focus needs to be precise as the depth of field is quite narrow even at large f numbers (small apertures).

Fg 2.
Kodak colour plus negative. scanned
 from print.

In understanding the way depth of field works you need to know that when you focus on the subject it is at that point the reflected light arrives at the focal plan as fine points of light (sharp). The subjects closer to the lens do not resolve as sharp until they are beyond this point and those further away reach pin sharp before they arrive, because of this they arrive as discs known as circles  of confusion. The larger the circles the softer the images appearance. By making the aperture smaller (large F number) you reduce the circles of confusion giving the picture the appearance of full depth of field. (sharp from front to back). The eye considers points of light as large as 0.25 mm diameter as sharp. The same applies to the dot pitch of a computer screen. When it come to the manufacturer of lenses for 35mm format cameras this figure is much smaller 0.08, this is because the maker has worked out  that on average a 35 mm negative will be enlarged by twenty times (a print size of 10 x 8.)

The good thing about using a film camera is that  you can check on how heavy the points of confusion will be by pressing the depth of field preview button. The advantage I have is I know what to expect from my lenses at particular apertures. This allows me to compose the picture with the amount of soft focus  I think will enhance it.

For example the three pictures included with this post.

•         Fg. 1 The main reason for the cats paw being out of focus is to add depth and a sense of being very close.

Fg 3.
FP4+ developed in ID11 printed on
Iford MG RC gloss

•         Fg. 2 The main reason for blurring the background is to exclude a large group of people walking towards me. They did not add anything to the picture I had in mind. By adjusting the aperture to a lager one (small F number) they have been removed making for a much better shot.

•         Fg. 3 The depth of field in this picture is very narrow. It took a bit of time in making sure that the whole of the ball was sharp and nothing else.

When taking a picture I consider the 'out of focus' as important as the area to be sharp.

 

The perfect print; possible?

It is still one of the most talked about subjects Visit any forum to do with photography digital or traditional and you will find threads relating to the perfect negative or capture. What developer to use, how to manipulate the raw file, what does a well exposed negative or histogram look like and so on. But this post is not about our digital friend or for that matter the negative it is to do with the photograph - the positive end of the process. I cannot get there without some negative chat first though!

After the recent deluge it is nice to be sitting back in the garden office writing this post and enjoying the late afternoon sun with my friend the cat. It is quite surprising how peaceful it can be in such a built up area. Not as negative as you thought but I digress.

It was Ansel Adams and Fred R. Archer that gave us a proven method of producing a properly exposed negative every time with the zone system. They divided the black and white negative up into eleven sections if you include zero from pure white to full black. Adams then said that really there are only nine zones if you are in pursuit of the perfect negative and then only seven of those will give texture. This is all well and good if you are using a plate camera but most of us don't. We use cassette and or roll film where all our carefully exposed negatives get a one time fits all development. In a round about way Mr Adams is saying that film sees the world in a more limited way to us. So we have all engineered ways of finding our perfect negative. What do I look for? A negative that has detail from high light to shadow and a good density above base clear in other words defined rectangles of tones the length of the film.



The day was very bright that the light
meter read a six stop difference
between the house wall in the background
and the shadow cast by the barn. I
over exposed the negative by two and a
half stops.

We all strive to produce the perfect negative but it was not until recently that it dawned on me that it does not necessarily translate to the perfect print. So what is the perfect print? One that is easy to print but what do they mean by easy to print? One that does not require a lot of dodging and burning. A single exposure success wouldn't that be the perfect print! With the way the negative sees the scene in front of it and all the variables in its path is it not inevitable that you will have to manipulate the image projected onto the base board of the enlarger to produce the perfect print? 

 

Recently I came close to my interpretation of the perfect print, one that does not require a lot of manipulation. By placing the test strip in such a way that the area that needed burning in was exposed to several different timed exposure segments this allowed me to add the extra time for that area to the first print. With experience the hit or miss aspect of the test strip process is lessened. It still doesn't take away that bit of a buzz when it all falls into place. Something I've never had with digital.