Enlarging len which aperture?

The quality of your enlarging lens will lead to better and sharper results at greater magnification. The aperture ( low number = large opening, high number = small opening) you set not only affects the amount of light it lets through but the depth of field as well. A good average aperture is F/5.6 in most cases. If the exposure times are to short a larger F number is needed, this will give you a chance to hold back shadow areas that may become to dark to show any detail. But don't get carried away and close down the lens by too  many F numbers as this may over heat the negative causing it to buckle, making the picture loose sharpness.

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.