We are encouraged to have projects - a specific idea, a goal to work towards. It might be in a specific location, or involve a limited subject but be in many locations, but in general we tend to think of it leading to ending up with a series of images which actually say something about a subject.
Often this is a requirement for publication or for contests, and is often recommended anyway as good for our souls.
A cohesive work tends to look better in a portfolio rather than the more common 'greatest hits' type of print collection most of us have hidden in paper boxes. I've written in the past that the ability to put together a portfolio on a single subject says a lot more about our skills as a photographer. One image on a subject might be luck, 20 is very likely skill.
So, you might wonder how you produce 20 distinct images on the same subject without repitition.
Let's pick a theme - say lighthouses. It would be very easy to produce a collection of light houses such that after the fourth picture, people start flipping through pretty darn fast, yeah, that's a light house all right, and another one, and another...
What we'd like to do is produce a portfolio which both hangs together from a certain degree of consistency, without looking so much the same that unless you were obcessed with lighthouses, the subtle differences would bore you.
We could photograph the lighthouses each with a different style, some contrasty, some light, some dark, some flat but this threatens the cohesiveness of the portfolio. It would be nice if the tonalities of the prints have some consistency while the compositions vary substantially. There could be a variety of weather and lighting, yet we'd like to be able to identify the prints as belonging together and coming from the same photographer.
It should be possible to include up close details of the lights, portraits of the lighthouse keepers (do they still have those?)as well as distant shots, possibly taken with a variety of focal lengths.
It's my opinion that the consistency should come from how the images are printed. There should be some consistency across the images in issues like highight and shadow handling, overall contrast. This may mean using similar lighting for the whole portfolio or you might have to copensate for high contrast situations with HDR techniques (a la Outbackphoto.com ).
This means that we may have to take this into consideration in selecting images for the portfolio and also in how we print them. We certainly need to compare the individual images with the others in the portfolio and may have to go back and reprint if one image stands out as looking like someone else made it.
It may mean that if we like a bit of variety in say, focal length, then we are best to really mix it up so focal length doesn't become an identifying feature of most of the images - eg. you can't expect cohesiveness if all the images but two use wide angles and the other two are strongly telephoto. A single pale image in an entire portfolio of dark images looks really out of place. If you are going to make substantial alterations to the images, best do it to all, not some.
Turns out making an attractive portfolio of images is harder than we might have thought but well worth the effort and I suspect that if you are submitting images, more likely to get the attention of editors, gallery owners and the like.