I have taken pictures of small things that, at the desired scale, took up to 11 MF frames to fit all of it in.
Something in there tells me i needed a larger format. For a small thing.
I see absolutely zero advantage for small format when doing macro. Zero.
Fine, but I do flowers, which generally do not fit into the 35mm frame ;)
Regarding the size of the equipment used, I'll just say that my rb and my cambo are very stable and allow me to use just about any lens for closeups well beyond 1:1, in fact, with the ability to tune magnification on the fly (no shuffling of extension tubes). And they use leaf shutters. Then there are the tilts that allow me to optimize DOF at wider apertures... All of which I consider to be very big bonuses.
Sure, when I am doing handheld macro shots of bugs, I'll use a 35mm. Incidentally, I am doing a fair amount of nonsense with a Mamiya 80/4 macro (for 645 format) mounted on a Nikon body. That lens is fabulous for macro, if you get sick of shuffling extension tubes (I do). Way more flexibility than a standard 35mm macro rig, and if there is any loss of sharpness, I am not seeing it (it's all a wash once you stop down anyway, how many 35mm macro shooters work at f/8? For a straight-down shot of a penny maybe...).
Bottom line, as usual, is that there are different tools for different tasks. My point was that there is no overriding reason why smaller formats are better for macro.
In the spirit of putting one's money where one's mouth is, I suppose I should end with an LF macro example. Shot on 5x7", with pushed hp5+. I do not think 35mm could have delivered the tonality I was after. Am I wrong? Really? If so then show me.
The reason your depth of field will be less is because you are focused CLOSER to the object (in terms of film format diagonals) with the large format camera. All else being equal (ie subject size, subject distance, final print size, absolute aperture 6mm or whatever, etc).
Indeed with pictoral subjects, the depth of field is nearly the same between large and small format cameras when absolute aperture diameter is the same. But once you move in close, the smaller format camera is always going to win in terms of depth of field. If you try to stop the larger format lens down to match the depth of field of the smaller camera, the smaller camera will win again, because its image will be sharper.
Here is a relevant thread: http://www.largeformatphotography.in...ad.php?t=38494
A bellows, extended, say, 130 mm. On it, a 16 mm Luminar, stopped down 2 stops. A 35 mm camera on the rear.
That produces a magnification of about 10 times, with the DOF and diffraction that comes with it.
Now that same setup, but with a 6x6 camera on the bellows, with the bellows extension reduced to 'compensate' for the longer camera body.
Result: same (!) magnification, same (!) DOF and diffraction.
But on a larger (!) format... ;)
That's the aformentioned 'magnification driven' approach.
But yes, if you want to fill the frame the same way, no matter what format is used, you need more magnification (= less DOF) using a larger format.
But for the reduced DOF you also get increased detail.
So it's not all bad at all with large(r) formats, even when using the "frame driven" approach. ;)
Now... would the absolute sharpest possible result be at f/8 or f/11 or so? Yes, sure. True of all formats. But for LF and some MF, that matters not one iota unless you are shooting res charts. The smoothness of the tonality and the focus transitions in medium and large formats matter a lot more (to me) than whether you can see some minor difference under a loupe.
Not to slam 35mm, which is wonderful for a great many things including some macro work, and which I also use happily, but... the transitions between in focus and OOF objects can be rather harsh in 35mm. You can see focus/defocus lines. With the larger formats, the transition from in- to out-of-focus portions is generally much smoother and more gradual.
Also, as I mentioned, a tiltable bellows gear can eke a lot more effective DOF from a wider aperture than a 35mm system with extension tubes. When I do macro with a view camera, I focus first of all with the lens wide open, then use tilts to bring as much into focus as I can, and then start stopping down, etc., if the DOF is insufficient.
I don't believe it has anything to do with diffraction, nor do i think the effective stop due to bellows factor is doing anything to create increased diffraction. I believe it is either the sharpness of the lens as a macro, or subject movement, or perhaps camera vibration. Could even be the developing (heavy metal agitator? :D), but I'm betting on some kind of movement or vibration with a 2s exp.