The Mirror slap is a topic of importance for me, because I tend to do a lot of close up work with ambient light or light bulbs instead of flashes. SLR Cameras without mirror lockup tend to show a certain degree of vibration blur between 1/30 and 1 second exposures due to mirror slap. This is most prominent when using long lenses.

I wanted to use my F90x for my close up photography, but I was concerned about the effect of mirror slap, because the F90 x doesn’t have a mirror lock up and I usually expose at times which are exactly in this critical area.

To determine the effect of mirror slap on this camera, i made a series of pictures with a 135mm macro setup. The focusing distance was at around one meter. the aperture stayed at 1:5,6 and the lens and the target weren’t touched throughout the test.

I used 20 second delay time release and made sure there are absolute no vibrations until the exposure was made. I took every shot two times. The light difference was made by an artificial light source, which was moved away from the target accordingly to create the same exposure on every shot. The shutter speed ranged from 1/60 to ¼ in full stop increments. I used Agfa APX 100 film in this test, I exposed it for ISO 80, and developed it in Rodinal in a 1+100 dilution over 10 minutes with moderate agitation.

The results can be seen here. The visible crop of this picture covers a surface of approximately 3 by 3 mm on the negative. 3 mm are 0.118 inch.

1/60 of a second,

Again 1/60 of a second,

1/30 of a second,

Again 1/30 of a second,

1/15 of a second,

Again 1/15 of a second,

1/8 of a second,

Again 1/8 of a second,

1/4 of a second,

Again 1/4 of a second,

1/2 of a second,

Again 1/2 of a second

I looked very carefully at these enlargements, but I couldn’t really identify any blur or some sort of difference between the exposure other than the usual variations you can expect from analog material. What do you think?

It seems to me, that under the circumstances I take pictures and with the material I use, mirror slap is not reproduceable. And therefore, nonexistent in this camera for me. This is really impressive, because the D700 which has Mirror Lockup produces quite hefty mirror slap blur in the critical exposure times without mirror lockup engaged. Maybe if other film material and other setups are used it may be visible, but for me it is an nonissue.