Tag Archives: math

Figuring Out F-Stops – Olympus Trip MD

Like the Konica Tomato/Pop-10, the brightest f-stop is the only one given in the manufacturer’s literature. Unlike the Tomato, I couldn’t find information on line so I had to do it myself.

If you don’t care how I arrived at these values and trust a random web page, here’s a table:

ISO Flash F-Stop
100 yes 4
100 no 8
200 yes 5.6
200 no 11
400 yes 8
400 no 16
1000 yes 11
1000 no 22

These values are rounded to the nearest whole stop. YMMV. Not responsible for ruined shots, hives, divorce, or any negative outcome resulting from the use of this information.

The camera is dark gray or black but the LED lights made it look blue.

Trusting that 35mm really is the focal length and f/4 really is the brightest f-stop:
35mm / 4 = 8.75mm diameter with the lens wide open.

You only get F4 at ISO 100 and the flash popped up.

You only get F4 at ISO 100 and the flash popped up.

The area is what’s important for exposure. Focal length/diameter=f-stop only holds for circular apertures. For most, I treated the shapes like diamonds and used (b x h)/2 for the area. To keep things simple, I cropped in to the edge of the lens and then resized to 875 pixels so 100 pixels is one millimeter. Once I had an approximate area, I used the equivalent circle area to get a diameter. SensorsOne has a great calculator so I could just plug in the area instead of using a calculator and working backwards from area=π r² every time.

ISO 200 with the flash came out to about f5 so I rounded it to the nearest full stop at f5.6

ISO 200 with the flash came out to about f5 so I rounded it to the nearest full stop at f5.6


ISO 100 w/o flash & ISO 400 with flash are ~ f8 (7.2 calc'd).

ISO 100 w/o flash & ISO 400 with flash are ~ f8 (7.2 calc’d).


ISO 200 w/o flash & ISO 1000 with flash are ~ f11 (10.3 calc'd).

ISO 200 w/o flash & ISO 1000 with flash are ~ f11 (10.3 calc’d).


The last one was still approximated to a diamond but I had to be more accurate as the apertures got smaller.
At ISO 400 & no flash, the shape got less diamond-like so 2 circles and 2 squares give f14.

At ISO 400 & no flash, the shape got less diamond-like so 2 circles and 2 squares give f14.


ISO 1000 w/o flash is a pill shape so a circle cut in 1/2 and a small rectangle approximate the area for f18.

ISO 1000 w/o flash is a pill shape so a circle cut in 1/2 and a small rectangle approximate the area for f18.