Your take makes good sense. I have heard that using a fixed lens prosumer camera at F/14 (their maximum) is like having an f stop of f/64 on an SLR (for depth of field), but with the advantage of F/14 for light gathering and definition.
One option (us "unfortunate" SLR users can try) is to take the photo from further away at optimum F-Stop (F/8 - F/14), and then to crop the part of your image you want to keep. Thereby you effectively use a smaller "immage sensor" (like using a prosumer digicam, but possibly with fewer megapixels), but have a much higher DOF (due to taking the shot from further away.
There is so much experimenting one can do, and options one can try, to try to optimise macro shots. All in all, one may find that using a bit of each method may all help when used together.
Hallo Bryan I think it all depends on the specific lense and may even differ slightly within the same model (as cars do). Every lense has its sweet spot where definition is optimal. You need to experiment with yours to find the optimal fstop. Personally, I am using the Nikkor 105mm Micro, which according to some tests I've read, looses definition quickly beyond F8/F11. If you look at my portfolio you will see that most of my macros were taken at fstops of f28 or f32 - Judge for yourselve about the definition. I think the overall improvement through increased DoF works in favour of the f32. We dont look at images pixel by pixel the way some technical tests are done, our minds take in the whole image. Depending on the subject, I would prefer 60% of the image at a definition factor of 90% against 5% of the image at a 99% definition factor if you follow my reasoning. In the end is all about your objective - what do you want to convey with the image. If its only the eye or the stamen gofor the higher definition/larger f stop, if you want to show detail of the whole subject, go for the smaller fstop (compare my two recent uploads of the Gazania flower)
Regarding the extention tube - you will loose light but not definition. You will get closer to the subject and therefore, restrict your DoF even more, requiring a smaller fstop to get more of the subject in focus.
By contrast, using a close-up filter, you will loose no light but you will loose definition due to often inferior glass used for the filter. Again, because you get closer, you will loose DoF.
By using a 1.5x or 2x converter you will gain distance from the subject and improved DoF, but you will loose about an fstop in light as well as definition due to the addage of several lense elements.
Thanks, Joggie. Your advice is well valued and I will be inclined to follow it at the next opportunity.
Just wondering if you also experience a noticeable softening of focus (from diffraction) when using very small appertures (eg F/32). I notice it very slightly, but can't decide if its detraction outweighs the gain you get with DOF.
I also heard that an extenton tube decreases the amount of light reaching the sensor by about one stop, and was wondering if this decrease has the same characteristics as using a smaller apperture (ie getting better DOF) without experiencing the diffraction issues. Just something to mull over...
Great detail in the in-focus areas Bryan. I feel you could stop down to f28 or 32 which would make a huge difference in the level of detail. Nice work. Joggie
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