Increasing depth of field (DOF)

Hyperfocal distance is not something that trips off the tongue in this modern age of auto focus. In fact digital camera lenses do not have the facility to take advantage of this compositional tool. You just have to compare today’s lens with yesterdays they don't have aperture settings and therefore you can not play with hyperfocal distance settings.

So what is Hyperfocal distance?

When a lens is set to infinity, the depth of field (D.O.F) closest to the camera is known as the Hyperfocal distance for that aperture. If you have an older lens its barrel will be marked with these distances.

How to change the Hyperfocal distance.

Set the lens focus to infinity, and then read the lower mark for whatever aperture you have set. If you then refocus the lens to the lower mark known as the optimum distance you will increase your depth of field by fifty per cent of the optimum.

For example:

This was made using a
 telephoto lens at close distance.
 The use of hyperfocal distance has
 pulled the area of sharp focus
to the front of the ball.

I have used an old 50mm Nikon lens (pictured) to show how it works. I have set the focus to infinity and the aperture to F16. The good thing about this lens is that it shows the upper and lower limits of each aperture with lines on the lens barrel. Looking to the right (marked A) you can see that the last line on the lens barrel is opposite the five meter mark (about fifteen feet). By resetting the focus to optimum in this case five (A). Then look at the lower limit (marked B) for F16, it is about two and a half meters (eight and half feet). The resetting will extend the overall sharpness of the picture by an extra two and a half meters which is 50 percent of the optimum.

The longer the lens the greater the increase is. For argument, an 80 mm lens with an aperture of F22 set, would have a depth of field from 2.8 meters all the way to infinity when optimum focus is used. Instead of 5.6 meters to infinity.

If  hyperfocal distance had been
used with this picture the
 front post would be sharp.
 

In some cases where you do not have aperture lines on the barrel of the lens some cameras and lenses have a shut down button. This allows you to see before you press the shutter where the hyperfocal distance ends. So you can adjust it if needs be.

Being able to increase the depth of field (D.O.F) can be very useful when using medium and long telephoto lenses for subjects close to the lens, allowing narrow fields of sharpness to be moved. This makes sure the front of the item is in focus.

Cropping your photograhs

Print of the whole negative

When it come to cropping your prints there are two schools of thought. Those that believe that once the view has been carefully framed in the camera, you should print the whole negative and in some cases include the rebate as well to prove it. The alternative view is that each image is unique and should be judged as such irrespective of its format.

My stance tends to follow the latter view or what best emphasis the composition whole frame or part of. It does not always follow that what your pre visualized view at the time translates to the baseboard when it comes to printing. 

It is important to consider how you're going to frame the image at the beginning of the printing process. The start of which is the contact print once produced time should be taken to consider what is best for each picture. In some cases it is an automatic decision how the picture is going to look. In others it is not quite so clear as to what is right. In these situations it maybe better to print the whole negative and use a crop tool to ensure what framing brings the best out of the image. 

Cropped for impact

Setting hard and fast rules when it comes to producing your pictures will prove detrimental in conveying the vision. It is better to keep an open mind and be bold in the way you frame your pictures. Sometimes it is good to seek other peoples opinions they may offer an idea that you have not considered, but remember these are suggestions that should not be followed blindly. You should only do what others indicate if you truly believe that it is the best for the composition and coincides with your vision for the picture.

I crop photo's for a number of reasons some listed below:

• 

  change story

  To remove unwanted items from the picture that sometimes get missed in the making process from around the edges.
• To correct a bad holding angel.
• To remove processing faults, dust hair etc.
• To change the balance and or emphasis of elements in the picture.
• To change the format of the picture.
• To remove dead areas from pictures tightening the composition.
• To create a better sense of intimacy.
• To improve composition.
• To tell a different story. If you are doing this then you should give serious consideration to the facts of the situation before changing the emphasis especially from a photojournalists perspective.

Crop tool.

You can use a crop tool which was mentioned earlier. It can help to improve how you compose images at the making stage. It is a way of training your eye.

Crop tool made from

They are simple to make as described below:

You can make a crop tool out of two bits of cardboard it needs to be 50 to 75mm (2” to 3”) wide and 500 x 400mm (20” x 16”) long or bigger than the largest print you are likely to make. If you do not want to make it completely from scratch then you can use a pre cut mount frame cut to make two L shapes. This allows the framing of the picture to be infinite.

This simple idea allows you to try out those more radical ideas along with the more prosaic to see if they work. It may surprise you in the process.

Split grade printing the next step dodging and burning .

Top grade Zero
Bottom grade five

The use of split grade printing has changed the way I work in the darkroom. Yes it takes a little bit longer having to produce two test prints, but in the long run it cuts down the amount of dodging and burning needed to achieve a finely toned photograph. I have also noticed a luminosity that has been missing from my graded prints. It has also shown me that it is an advantage and not a waste of paper to make full or half page test strips. You get a better understanding of how much more light is needed for the high lights, so you can build this into the first full print of the scene. This saves time and paper having to reprint it again and again to get it right.

I find that my more contrasty negatives are more easily printed using the split grade method, giving more control of not just the tones but also the contrast. Burning or dodging my prints has been reduced considerably, allowing me to add more detail at the extremes. 

So at what point should you be burning in or dodging? The grade zero exposure being the most important one is also the stage at which you should be making your adjustments. If possible you should be including them for the grade five test strip. By doing this you will have a better understanding of how the contrast affects the corrections and make allowances for them in the final print.

Some of you reading this will be thinking it's all to complicated and not for you, Dodging and burning is about having confidence in your ability, once you have done it and seen how it changes your pictures for the better, you will be wanting to do it every time. I enjoy this part of the picture making process, it always reminds me of a composer on the rostrum encouraging certain section of the orchestra to bring out his interpretation. Only you are using light to enhance what you had in your minds eye.

Burning in graduation times

OK I'm going to keep this simple just to give you the idea of what to do. I have only used grades 0 and 5 but in certain cases other grades maybe more appropriate but that is for another time.

Producing the prints:

I produced a soft toned (grade 0) test print at five second intervals. When it was dry I compared the segments to determine which would give the best overall toned exposure and how much extra light would be needed for the sky. I chose seven seconds for the whole picture, this allowed the street scene shadow to keep its detail without it blocking out. A further twenty one seconds would be added to the sky. With the main exposure done the sky was burned in. For this I used two black pieces of card held together to form a V shape. The trick with dodging (holding back the light) or burning (adding light) is to keep the mask moving otherwise a hard line will be left. I gently moved the card backwards and forwards lingering in places to give the sky a graduated look. The times on the picture are there as a guide.

Now I placed some black card over the masking frame to protect the picture from any stray light, while I adjust the enlarger to grade 5 for the contrast exposure. The first segment was covered and then exposed at two second intervals there after. Again when dry I chose 3 seconds.

Final print

With the all the times combined a full print was made. There are some short comings; firstly the build on the left could do with a bit more burning in to bring out the texture of the wall and if I wanted to be really picky the sky could do with masking in more precisely which would mean cutting a mask that mirrored the buildings outline.

 

The idea was to keep it simple and to show what could be achieved with the most rudimentary of masking off.

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.

 

Dodging and burning.

A selection of dodgers 

They are darkroom tools to help bring out all the detail from your negatives when printing. 



Holding back

No matter how well you expose and develop your negatives, when it comes to making a positive you will need to equalize the exposure by holding back and burning in to keep the detail in the highlights and shadow areas. In a lot of cases it is not possible to alter the overall exposure time to take these deficiency's in to account. In these cases dodgers as the name implies will help you get round this problem. You can use your hands, fingers, pieces of card, a length of wire with a cut out of  card stuck to it and cards with holes in them. 

Burnning in

Dodgers work by casting a shadow over the area that needs less exposure than the rest of the picture. Likewise dodgers with holes in them are used for burning in areas that require more light than the rest of the photograph. This is also a type of holding back as it stops the correctly exposed picture from becoming over exposed. When using a dodger you must keep it moving otherwise it will produce a hard outline to the area you are trying to correct. It can be moved from side to side or up and down to stop this happening. The amount of time you use your dodger for will depend on what your test strip shows.  If you have not got a test strip then it will be trial and error taking a number of prints before you get it right. With experience the amount of error will diminish. 

Dodgers are not just for correcting problems, they are there also for creative purposes for example to bring out some extra drama in the scene, add a shaft of light where there was none or to bring two pictures together where one maybe lacking any sky detail.