DaveB wrote:ATJ wrote:DaveB wrote:Are you sure you took these images with exactly the same angle towards the tape measure?
Yes. Positive. I had the camera mounted on the tripod and did not change anything other than the lens.
But you must have changed the distance to the subject, no? Which bits of the setup moved?
Well, yes.
What I did was as follows...
* Set up the tripod so that the head was angled down at 45º
* Mount the camera on the tripod and the 60mm lens on the camera
* Set the 60mm lens to its closest focusing distance (21cm which gives 1:1)
* Adjust the height of the tripod using the centre column* so that the point of focus was as close as I could get to the centre of the lens
* Adjust the ruler so that the 10cm mark was at the centre and the ruler was straight
* Take a series of photographs from f/4 through to f/57
* Take the 60mm lens off the camera and put the 200mm lens on the camera
* Set the 200mm lens to its closest focusing distance (50cm which gives 1:1)
* Adjust the height of the tripod using the centre column* so that the point of focus was as close as I could get to the centre of the lens
* Adjust the ruler so that the 10cm mark was at the centre and the ruler was straight
* Take a series of photographs from f/4 through to f/45
I have taken another series of shots this time using 1mm graph paper. I went for a lower angle that 45º. The contrast in the images has been increased significantly to better show up the differences. These two shots were taken at f/11.
They appear to show little difference in DOF.
* Yes, I know it is not a good thing to raise the centre column but I was not after rock solid stability but simply consistency in the shots. Plus I was shooting with flash so it would freeze any camera movement.