[Anvh]

Yet another strategy: use a compact. Ricoh says that the GRD IV at 1cm will capture an area approx 26mm x 19mm. Now this is the same area as APS-C at 1:1 but, given the size of the compact sensor, is more like 1:3. For a given magnification, DOF is independent of focal length (it's simply working distance that changes) and 1:3 gives you lots more DOF than 1:1.

I get what you're saying, you don't need to focus so close because of the smaller sensor if you're looking at the "frame" didn't thinking of looking at it that way.

the 1:1 and 1:3 you're using isn't correct though.
These values are interdependent of the sensor size, it simply looks at the size ratio of an object and how much the lens magnify that.

So 1 centimeter in real life is displayed by the lens as 1cm as well on the film plane at 1:1
At 1:3 an 3cm object is displayed like 1cm

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Last edited by Anvh; 05-08-2013 at 02:51 AM.

[scratchpaddy]

Smaller sensor actually makes the DOF smaller.

Circle of confusion, indeed. I'm thorougly confused. Okay, jatrax says I shouldn't do this, but... how can that possibly be true? You said earlier that magnification is all that matters. My point is that, to enlarge a subject to the point that would be 1:1 on APS-C, you'd need considerably less than 1:1 magnification on a smaller sensor. That's more DOF, right? If not, shooting further out and cropping like top-quark said would also be an invalid strategy. A small sensor is just an automatic crop.

Edit: nevermind, forgot to refresh before posting. We're on the same page now, right?

[Anvh]

I think we are but i'm going to write it down anyway for the completion.

What matters
- Magnification (lens) - How much the lens magnify the subject (and nothing more is to it)
- Aperture (lens) - lens opening
- pupil magnification (lens) - this one only really matters with close focusing. it's hard to explain but it's a kind of magnification that happens inside the lens itself. With normal lenses this value is 1 but with telephoto lenses, so lenses that are smaller in size then their focal length this value is smaller and with retro-focus lenses (wide angle) this value is larger. With wide angle you can really see the effect, you've this huge front element but the rear element is normal in size.
- Circle of Confusion (sensor size) - an image is made out of points, think about those highlight points you sometimes see in the background blur, your image is build up with them. CoC is the maximum size these can be to make it appear sharp at typical print and viewing distance. These points the lens make on an FF sensor or APS-C are the same size BUT you if you for example print the photo on poster size the those points need to be enlarged more with the APS-C sensor and as such the size of the points need to be smaller to appear acceptable sharp at that print compared to FF.

I hope i explained that good enough.

Now what top-quark is saying is to match the "print size" of the subject.
When you think about it, APS-C is enlarged more then FF, 1.5 times if my math is correct.
So that means you can lower the magnification of the lens as well. So if you need 1:2 with FF then you can use 1:3 for APS-C and that would increase the DOF with quite a bit


ps. Guus als je de uitleg in het Nederlands wil hebben is dat geen probleem. Hoe wel dit wel een technische verhaal is inplaats van praktische.

[ruggiex]

@Anvh thanks for clearing that up. I def had misunderstood some parts before.

[top-quark]

Adding my own clarification.

Yes, I was talking about what you get in the frame rather than drawing any equivalences between expensive macro lenses for big cameras and the diddy little things on compacts. GRD IV at closest focus should show pretty much the same image in the frame as, say, the DFA 100mm at closest focus. And because the actual magnification is lower with the compact you should have more DOF.

To use the example of the GRD IV again, you will, of course lose some absolute resolution (10MPx vs. 16MPx or whatever), but you should gain apparent detail by having more in focus. But then you might lose some by having a lower F-stop threshold where diffraction starts destroying detail (an APS-C camera should be, what, two or three stops better here?). Regardless, do a web search for "GRD IV macro" - there are some very impressive images out there. I've also heard that the GRD IV autofocuses well at closest distance, whereas with a dedicated macro lens on a larger camera you'll be manually focusing.

Question for those who've used such a thing: can a Raynox close-up lens or the like give you more DOF for more macro shots? Typically, you'd use one to get more magnification but you can you also use it to give you the same magnification from further away?

[BrianR]

Try f/16 or f/22 or even f/32. Don't be afraid of diffraction until you've gone there yourself, you may find the overall loss of sharpness from diffraction to be worth the extra depth of field and convenience over focus stacking.

You can also keep more in focus by recomposing so the important bits of the subject are in the focal plane or as close to it as possible. For example, in the bug you posted, you could keep the tip of the tail to the head in focus if your camera sensor was parallel to the body of the bug. Shooting down from a good angle could keep it's back left legs in focus as well. This isn't all or nothing, it's a gradual trade off between your desired composition and getting more in focus and is worth keeping in mind.

[Digitalis]

Also using off camera flash can help - skilful use of lighting on the subject can make DOF appear larger than it actually is.

[Anvh]

Question for those who've used such a thing: can a Raynox close-up lens or the like give you more DOF for more macro shots? Typically, you'd use one to get more magnification but you can you also use it to give you the same magnification from further away?

From what i understand it magnifies and since DOF depends on the magnification and aperture, so if you end up with the same values then the DOF would be the same.
At least that makes sense to me unless the filter does something different.

[desertscape]

Since light rays enter the lens for macro work in a diverging manner, the image is in focus behind the focal plane. Tubes solve this by allowing the lens to be used at a longer focal length and therefore the focal ratio also changes. The idea of using a positive element (or sometimes an achromat) in front of your lens, is that it bends those diverging macro rays so that they are close to parallel, as when shooting at infinity and so can form a usable image at the focal plane without tubes. The focal ratio does not change and I don't believe the DOF would either.

[hangman43]

I uploaded a maco yesterday (https://www.pentaxforums.com/forums/post-your-photos/224040-macro-we-one.html#post2376841), which demonstrated my problem with macro's. I cannot get my close-ups sharp from back to front. And I wonder how is it done? The above picture was made with a smc pentax 100mm macro, which should be good enough.
I could solve the problem by focussing differently in different photo's, but that might be awkward in live-shooting insects.
What could I be overlooking ?

Try to get the insect where the head and tail are the same distance from the lens and is in the middle of the area in focus this insect was larger than your Midge picture and I got most of it in focus this was shot at F/16 at 1:1 magnification




This Mosquito was shot at F/16 with 105mm Macro with 65mm of Ext Tubes




Notice how I shot it more head on so not as much in focus but you can see the line that is in focus if I would have shot from more of the side of it would have got more in focus

[guus giesbergen]

them are 2 very nice macro's Hangman43, and I hope to be able to get such quality. What camera and what glass did you use ? I have a K5 and 100mm pentax 2.8, that should be good enought, I guess.

[hangman43]

them are 2 very nice macro's Hangman43, and I hope to be able to get such quality. What camera and what glass did you use ? I have a K5 and 100mm pentax 2.8, that should be good enought, I guess.

I use a K-5 with a 105mm Lester A.Dine F/2.8 Macro

[MSL]

Also using off camera flash can help - skilful use of lighting on the subject can make DOF appear larger than it actually is.

Can you clarify by what you mean by this? For off camera flash are you talking something like a ring flash or an extension hood for a standard flash or are you talking wayyyyy off camera? In what way is it enhancing the DOF (and feel free to use the image you posted to elaborate)?

[Digitalis]

are you talking wayyyyy off camera? In what way is it enhancing the DOF

I'm talking about moving the flash off camera with the light striking the subject at an acute angle, doing this enhances contrast - this boost in contrast makes it appear that the DOF is larger than it really is.

[JimJohnson]

Trailing Arbutus...
I didn't bring my macro gear with me this weekend. The best I had was my F35-70 with its so-called macro mode (actually just close focus) and my Sigma flash. Digitalis is right on with his comment about acute angle. Trailing Arbutus is a small fragrant blossom found only in the wild, close to the ground and typically in deep shade. I found a white plastic chair nearby and flipped it over on its back to use the bottom as a reflector about 30-40 degree offset from my lens. I put the flash on camera and swiveled the head to bounce off the chair bottom. It was about the only way I could light the white blossoms and retain the texture without blowing out the highs. Folks were waiting, so this was the best I could do in about 10 minutes time.