Adam Monk Photo Tours & Images Gallery

DOF

Depth of Field (DOF) confuses many people, especially in relation to medium format cameras Vs 35mm format cameras.  Why do lenses that give essentially the same view on their respective format, say and 80mm on medium format and a 50mm on 35mm format,  exhibit dramatically different DOF, even at the same f-stop?

Firstly, what is Depth of Field?

The focal point of a lens is in fact a focal plane, a flat 2 dimensional field out in front of the lens where everything is actually and truly sharp (assuming a good quality lens), that is, a point in our subject focuses to a point on our film or sensor.  This plane shifts forwards and backwards as we move the focusing ring of the lens and is usually parallel with the film or sensor plane of the camera.  The DOF is the range fore and aft of this focal plane that appears to be sharp in our final image.  It is not actually sharp, in the strict definition of the word, but each point (from our subject) forms a circle of confusion on our sensor that is sufficiently small as to appear as a point in the final image, thus it looks sharp. This Depth of Field, also known as the range of acceptable sharpness,  is effected by 5 primary factors…

1. The focal length of the lens:  The shorter the  focal length, (wide angle lenses), the greater the inherent DOF at all relative apertures.
2. The aperture used:  The smaller the aperture, the smaller the Circles of Confusion will be.  Rendering more of the image with the appearance of being sharp… up to a point.  Beyond that point (this will differ for each lens), diffraction through the lens will start to have a significant effect, this will soften the overall focus regardless of the DOF increase.  Once the aperture declines below a point where the DOF blur is smaller than the diffraction blur, the image will begin to increase in sharpness again.  So some lenses with a big aperture range  can actually become sharper  at the extreme end of their  scale (such as f45 or f64).  Many large format lenses, particularly those made for landscape photography, are actually optimised for maximum f-stop use, and can be rather soft when used with less than this extreme aperture.
3. The subject distance:  The closer the subject is to the lens the less is the apparent DOF, especially when taken to extremes in macro photography, when DOF can be measured in fractions of a millimetre.
4. The format of the camera used:  The larger the format of sensor or film used the higher its resolving power, and the greater the level of detail it can record.  To create a print of the same size the medium format image requires far less enlargement, thus the larger the Circle of Confusion size can be and still appear sharp (in the same size final print).  Thus, for the same focal length, at the same subject distance, the same f stop, the greater the apparent DOF in the final print for the medium format sensor over the smaller format for the same size print.
5. The enlargement of the image:  The more an image is enlarged the less DOF it will exhibit.  The circles of confusion that appear sharp in smaller prints (or screen enlargements) will become more obviously soft, both forward and behind the actual focal plane, effectively narrowing the DOF.

Depth of Field and Medium format cameras

If the same image is taken with two different format cameras, say a 35mm camera and a medium format camera, at the same subject distance, the same f-stop, with the same focal length lens  and the resulting images are printed  to the same size, the medium format image will have greater apparent DOF.

An 80mm lens is an 80mm lens  whichever camera its on, the focal length at infinity is 80mm and its DOF is a constant factor of the f-stop used.  What changes is how much of the image projection is included in the frame,  the angle of view.  A 35mm camera has a film area (or sensor) of 36mm x 24mm, whereas a medium format camera has a much larger area of film or sensor, usually between 60mm x 45mm to 60mm x 70mm. This is a considerably bigger area so the sensor “sees” a much wider view of  the image the lens is projecting, which changes the perspective to a wider field of view.

So effectively, the same focal length lens can be a telephoto with one format, but a wide angle in another, as illustrated in the example below.  This is an image shot on a 6×17 format camera with a 105mm lens.  It gives a very wide field of view, and a 105mm is considered a wide angle lens on this format camera.

The cut out outlined in black is a 35mm film format size.  What you would get if you shot the same scene, from exactly the same place with a 105mm lens (with the same exposure settings) on a 35mm camera, and you can clearly see it is a medium telephoto field of view.  Obviously both will have the same DOF.  This is a real example, it’s actually what you would get if you stood in the same place with the two cameras and took the same shot on both with the 105mm lens… Or, you could simply take it on the 6×17 camera, develop the film, and take a pair of scissors and cut out a 24x36mm rectangle, and get exactly the same result.

A 35mm perspective size cutout, in a shot taken with a 105mm lens on a 6x17cm large format camera

 Large Depth of Field

What seems to be the difficult part for people to understand here is the field of view, and how the DOF relates to it… in short, it doesn’t relate at all.  Although a 50mm lens on a 35mm format camera and an 80mm lens on a Medium format camera give you a similar field of view, they will not give you the same DOF for a given aperture.   It’s an easy mistake to make, to assume because your angle of view looks the same, your DOF will be the same too… But DOF is dependent on Focal length, not field of view, so the 80 mm lens on the medium format in fact has the same DOF as an 80mm lens on 35mm format (for the same aperture).

The Way it was

Back in the good old days (I’m showing my age here) when photographers shot on a variety of formats it was no problem.  We all understood that how wide a lens’s field of view is, is determined by the format of the camera its used on.  We also understood that DOF was not determined by this field of view, but by the actual focal length of the lens (and the f stop used).  So you would just shift gears with each change in camera format, and understand that, for example, a 90mm lens on a 5″x4″ (12 x 10cm) camera was a really wide lens, whereas on a 6x6cm medium format it was a slight telephoto, but the DOF at the same aperture would be the same (excluding the enlargement factor).

The new Issue

Since the ascendence of the 35mm film or sensor format they have become the benchmark and since most people never use other formats they never see the possible variance.  Thus a normal lens is 50mm, a 100mm is a telephoto and a 35mm is a wide angle… all the time.  While everyone is shooting the same 35mm film format that is fine, but then the camera companies started coming up with APS c sensors, micro 4/3 sensors and all the other tiny sensors in smaller point and shoot cameras and phones.

My Fuji point and shoot camera has a zoom lens that they have very kindly converted to 35mm speak as 28-112mm, which is about what it looks like on the screen at the back.  The 28mm end of the scale looks nice and wide and pretty much how you would expect a 28mm lens field of view to look, and the 112mm end of the zoom gets up nice and close like a small zoom should…

But then I read the fine print in the manual and the lens is in fact a 7.1-28.4mm zoom… so what?  Well, what it means is that at full zoom, at what looks like 112mm (in 35mm speak), I get the DOF of a 28mm lens, which has just about everything looking sharp, even with the aperture wide open, which is almost never what you want with a telephoto lens.  So you see now we have the opposite problem to previously, now people are getting far more DOF than they expect and our images are looking flat…

More news for the Kimberley Photographic Tour for May 2011, I have been talking to Ben from Team Digital about these fantastic F-Stop camera bag they are now stocking.  I love the bag so much (and i paid for mine!), that i think everyone who loves hiking and photography should have one.

I’m also talking to Team Digital about borrowing a medium format digital for the duration of the tours for participants to try out, probably a Phase One camera or the new Pentax.  We already have a Gigapan to play with, a medium format digital would be a great addition.  I’ll tell you more about this in the next few days too, stay tuned.

Kimberley Photographic Tour

Speaking of the Kimberley, my 7 day Photographic tour of the Kimberley and the 7 day  photographic tour of the  Bungle Bungles, are rapidly approaching, May the 16th and then May 24th.  Both of these tours are currently more than half full, so there are only a few places left.  To help us get all our booking done early we have decided to offer a discount of $250 for each tour for everyone who books and pays in full by Feb 28th.

Both these tours are a great opportunity to see the real Kimberley with 2 experienced professional photographers who love the Kimberley and have been there many times.  You can read more about the 7 day Kimberley adventure tour  here, and you can read more about the 7 day Bungles adventure tour here. Or you can download the information and booking pdf.

On May the 16th we will be leaving Broome and headed out onto the Gibb River Rd for 7 days of awesome photography, hands on masterclasses, hanging out in magical wild places, swimming in beautiful waterholes and watching the sunset in the Kimberley sky.  Then on May the 24th, we will leave Kununurra for the beginning of the second Kimberley Photographic adventure tour, 7 days camping in Purnululu National Park of exploring and photographing the Bungle Bungles.

Both of these photographic tours have a maximum of 8 participants with 2 professional Landscape Photographers.  We are travelling in Air-conditioned comfort in serious 4WD vehicles.  All meals provided and cooked for you, all camping gear is provided.  We will be at the most beautiful locations, at the best time of day.  The helicopter flight over El Questro station is included in the Kimberley tour, no extra cost.  The helicopter flight over the Bungles is included in the Bungle Bungles tour, no extra cost.

If you would like to see more shots from the Kimberley Region, click here. For all the latest Photographic Tours and Photographic workshops with Adam Monk click HERE>

The Kimberley Marine Parks the  West Australian Government have proposed in the far North Kimberley region of Camden Sound are part of   the worlds largest Humpback Whale nurseries.  They are doing this as an attempt to distract the Australian people from the real issue of industrialising the Kimberley, beginning with the enormous James Price Point Kimberley gas project. They are trying to buy us off.  How the two are connected beats me, instead of saying the Kimberley is unique and we will protect it all (as should be the case)  they have said, the Kimberley is unique, so we’ll put aside a bit of it before we set about ruining the rest.  Obviously these words are mine, but if you read the documents you’ll see that my paraphrasing is correct.

The Far North Kimberley Coast, Western Australia

The Marine Sanctuaries as they are proposed are woefully inadequate with only 13% of it offering any real protection from commercial fishing and other industrial activities, which of course defeats its own purpose.  It becomes a Sanctuary in name only until our pro multinational government decides to sell it off to the highest bidder.

Until the 1st of February you get to have a say on what you think of the  proposal, so go to this link, have a read of the letter, do some research, look at some maps and if you agree, submit it.

Low tide at Dawn on the Kimberley Coast

I have been up to the Kimberley many times, and 2 years ago i had the opportunity to go on a boat trip through the Far north and see a lot of this isolated and beautiful coast that you can only get to from a boat.  It really is like nowhere else on Earth,  a unique place that should  be preserved.  The only reason this government  can get away with selling off the Kimberley is that few people have seen it and so most don’t know how special it is and  what we would be giving up.

I want to be able to show my Grandchildren the Kimberley, the wild untamed Kimberley, not a barren industrial dump that it will become if these greedy and unthinking men get their way.  Do yourself a favour, if you’ve not been to the Kimberley, go.  it will get into your blood and touch your soul the way few places can, and then you too  will know why this is one place we cant let the greedy bastards ruin.

Early morning light reflected off the King Leopold sandstone cliffs

This magical little spot was just a short walk from the room we rented just outside of Nas on the Greek Island of Ikaria.  It is a small pool in the Chalares Gorge which cut right through the landscape below the balcony of the room and ended at the beach shown in the previous post. This spot is cool, shady and tranquil, perfect spot to lean on a tree and read a book or just do nothing…

Tranquil Reflecting Pool. Chalares Canyon, Ikaria

Shot on the Canon 5D Mk2 with the 16-35mm f2.8L lens at 16mm.  10 images stitched with PT Gui on a Mac (of course!)