Macro help with focus and DoF

[Just-Clayton]

Here you go Lawrence. I took 2 shots of my wife's flower. The first up close the second back a foot or so. Notice multiple parts in first are blurry, due to dof narrow. the second was cropped to simulate the closeness of the first. View attachment 141256View attachment 141255

 

[Lawrence]

Some more about the advantage of not shooting as close as possible.

At 1x with my current cam I'll have a DoF of about 0.5mm (a guess) around f/8. That ain't much. If I close down to f/32, I have some 2mm. That still ain't much if you look at the size of an average bee.

Now instead of closing down and neurotically trying to get into the end-zone of my magnification, I shuffle slightly back and shoot at 0.5x. At f/8 now my DoF is also 2mm but if during the first I was shooting at let's say 1/250s shutter, by now shooting slightly further, I can use the 4 aperture stops required for f/32 and invest those in shutter. Now I can take the same shots, albeit half the magnification, and shoot at 1/4000s.

I can shoot a sharp shot at 1/4000s when drunk. And while tumbling down the stairs.

Head first.

I understand most of this but never thought to get drunk to get it right. Anything is worth a try.

Seriously though - thanks. i do understand what you are saying and it all makes sense.

 

[Lawrence]

Here you go Lawrence. I took 2 shots of my wife's flower. The first up close the second back a foot or so. Notice multiple parts in first are blurry, due to dof narrow. the second was cropped to simulate the closeness of the first. View attachment 141256View attachment 141255

Thanks mate. There is alight flickering somewhere in my head

 

[J-see]

Here's an example. The shot is far from perfect and went the way of the Dodo long ago but it's what I had available on this PC.

The first is 3k*4k and I took a detail at 100% out of it. The second I doubled up in PS using bicubic smooth. I simulate crop/doubling. The shot is now 6k*8k. I didn't bother resharpening or adjusting anything else; I simply and quickly scaled it up.





Doubled:





There are limits to blowing up a shot and there are improvements to what I do here but it's just to show the initial size isn't always that important.


Edit: The detail shots are placed next to the wrong full. That well I noticed the difference myself at first sight.

 

[wornish]

Take the guesswork out of the DOF calculation.

Here is a great site.

You can load your camera and lens details and it shows you the DOF for each aperture setting and the effect of distance.

Depth of Field Table

 

[J-see]

Maybe I overlooked it but that's DoF for normal shooting.

In macro, DoF is calculated in relation to magnification and focal length is of no importance. I don't know if there is a DoF macro calculator out here.

 

[Lawrence]

[MENTION=31330]J-see[/MENTION] those images are pretty impressive. Once I get something in focus I want to learn how to do that.

 

[J-see]

@J-see those images are pretty impressive. Once I get something in focus I want to learn how to do that.

It's shot against the light which makes it look strange. Believe me, when zooming in, it's far from impressive.

For DoF I use a quick and rough formula.

At 1:1 your DoF at f/n is always a fixed size. That never changes for your cam even if you would add a longer macro lens. If you find the sharpest aperture on your lens, you only have to find out the DoF for that aperture at 1x.

Then it was something like: (f/n)/4 = DoF*4 = 1x/2 (0.5x)

For every four stops you close down, you increase that DoF by 200% which can also be gained by halving your magnification. Every two stops would roughly lead to a doubling which equals using one quarter less magnification.


Distances are hard in macro but it's fairly easy to guess the size of a bug. You also know your sensor size so while looking through the viewfinder, you can quickly estimate the magnification you are at and use that to adjust to the DoF you prefer.

My formula is a rough estimate but it's easy to remember once you have your starting number. For exact numbers, you'll have to check them for your cam. I need to recheck mine for this cam too.

 

[Lawrence]

It's shot against the light which makes it look strange. Believe me, when zooming in, it's far from impressive.

For DoF I use a quick and rough formula.

At 1:1 your DoF at f/n is always a fixed size. That never changes for your cam even if you would add a longer macro lens. If you find the sharpest aperture on your lens, you only have to find out the DoF for that aperture at 1x.

Then it was something like: (f/n)/4 = DoF*4 = 1x/2 (0.5x)

For every four stops you close down, you increase that DoF by 200% which can also be gained by halving your magnification. Every two stops would roughly lead to a doubling which equals using one quarter less magnification.


Distances are hard in macro but it's fairly easy to guess the size of a bug. You also know your sensor size so while looking through the viewfinder, you can quickly estimate the magnification you are at and use that to adjust to the DoF you prefer.

My formula is a rough estimate but it's easy to remember once you have your starting number. For exact numbers, you'll have to check them for your cam. I need to recheck mine for this cam too.

I'll need to look at this and try and make sense of it in the morning. What is f/n and what is x?

 

[J-see]

I'll need to look at this and try and make sense of it in the morning. What is f/n and what is x?

I realize I've been talking too much in my own language again.

F/n is simply your sharpest or most common used aperture when shooting macro. For me that was f/7.1. The x is for magnification. 1x is when you shoot at the max of your lens which is 1:1 (when the measurements of your subject equal the measurements on the sensor). A 10mm bug will be 10mm on your sensor.

For every two stops you open, you halve your DoF, for every two stops you close, you double it. Or you can adjust magnification to get the same result; 1/4th less magnification doubles DoF, 1/4th more halves it (when using 1:1 as a base).

 

[Eyelight]

The DOF calculators are not as useful in macro because the distance used in the calculation is from a point in the lens that is generally unknown.

There are some magnification based DOF calculators, but they don't seem very accurate. And DOF is somewhat subjective anyway.

My thinking is, since the aim is almost always to increase DOF to the max, there is not much reason to calculate. Just go small on aperture and if needed back up a little.

 

[J-see]

I am a bit the opposite (not a surprise I guess). DoF in macro is close to nothing so why would I invest more stops of light in more of that nothing?

I want my lens to shoot at its sharpest and that's it. I'll close down when there's nothing else left to put those stops into and light forces me.

 

[Eyelight]

......For every four stops you close down, you increase that DoF by 200% which can also be gained by halving your magnification. Every two stops would roughly lead to a doubling which equals using one quarter less magnification.
.......

For every two stops you open, you halve your DoF, for every two stops you close, you double it. Or you can adjust magnification to get the same result; 1/4th less magnification doubles DoF, 1/4th more halves it (when using 1:1 as a base).

DoF in macro is close to nothing so why would I invest more stops of light in more of that nothing?......

Halving or doubling nothing would be nothing, so I suppose the earlier statements would still be accurate in light of the most recent.

 

[J-see]

Halving or doubling nothing would be nothing, so I suppose the earlier statements would still be accurate in light of the most recent.

I closed down like crazy when starting macro and my "ahum" formula is of those days but I step back now and crop. That does not come at the expense of sharpness or shutter.

But realising not many shoot like I do, I mention the pricy method too.