Author Topic: Advice on DOF? (Read 8139 times)

RaFaLe · « **on:** April 01, 2009, 04:07 »

Hi all,

I have a Canon EOS 450D.
I'm currently using a Sigma 18-200 f3.5 OS Lens, as well as a Sigma 105mm f2.8 EX DG Macro Lens.
I'm loving the Macro lens, however, I need a little advice on this?

I'm struggling with Depth of Field in general.
My focal points are very sharp, but seems anything a few mm before or after that focal point is blurred.

So, in an attempt to increase DOF, I've increased F-Stop values using Aperture Priority mode.
The problem with this is that, naturally, my Shutter Speed (I hate this term) or Exposure Time (ahh, much better) increases.
So that's ok. I usually have a tripod set up, however, for bugs that happen to be moving, this poses another problem.

Of course, since the 450D is not a full-frame DSLR, I tend to try steer away from sensitive ISO speeds.
I tend to normally shoot between 100 and 400 ISO in an attempt to avoid excessive noise.

I've taken pics of water droplets on a leaf in a garden using f-stop 29 (Av), 1/4 Tv, ISO 200 in good morning light.
The DOF of the leaf (which is probably about 6cm in size) is still fairly shallow.
The middle of the leaf, is perfectly in focus, but the front of the leaf (about 2.5cm nearer to lens) is very soft.
It's a lot better than the same image at f-stop 11, but still shallower than I'd like.

Even shooting a miniature orange (which is about 3 cm in diameter), still shows sharp focus on the front, but blurring on the edges, only possibly 1cm deeper than focal point, using Av of 14-19?

Am I doing something wrong?

Something else I can try for increased DOF?

sharpshot · « **Reply #1 on:** April 01, 2009, 04:19 »

Usually there just isn't much DOF with macro. Using a tiny aperture might help a bit but then the lens can produce softer looking photos. You could try focus stacking with non-moving objects. I tried combineZP, it is free and works quite well. For moving objects, a ring flash might help.

Sometimes shallow focus can look good but a few of the sites reject them, perhaps because the reviewers don't know enough about macro photography.

Danicek · « **Reply #2 on:** April 01, 2009, 04:23 »

I think the ~ 170 mm eq. you have has direct impact on your DOF, something bit shorter (around 100 mm) could be a better compromise between DOF and needed distance (to not make your bug run away).

RaFaLe · « **Reply #3 on:** April 01, 2009, 04:33 »

Quote from: sharpshot on April 01, 2009, 04:19

Usually there just isn't much DOF with macro. Using a tiny aperture might help a bit but then the lens can produce softer looking photos. You could try focus stacking with non-moving objects. I tried combineZP, it is free and works quite well. For moving objects, a ring flash might help.

Sometimes shallow focus can look good but a few of the sites reject them, perhaps because the reviewers don't know enough about macro photography.

Thanks, sharpshot,
I considered that possibility, that perhaps some reviewers don't know enough about Macro photography.
I guess I could try focus stacking for non-moving objects - not a bad idea at all.

Just a question though - how would a ring flash help with DOF on moving objects?

peep · « **Reply #4 on:** April 01, 2009, 04:37 »

I remember seeing advise somewhere in forums about not using smaller aperture than about F16 for stock photos but I cannot remember why. F29 seems really tiny. I can set F32 on my lens but I have never done it so far. What aperture do you usually use for macro and for some isolated small object you intend to upload to microstock?

RaFaLe · « **Reply #5 on:** April 01, 2009, 04:58 »

Quote from: peep on April 01, 2009, 04:37

I remember seeing advise somewhere in forums about not using smaller aperture than about F16 for stock photos but I cannot remember why. F29 seems really tiny. I can set F32 on my lens but I have never done it so far. What aperture do you usually use for macro and for some isolated small object you intend to upload to microstock?

I normally use an aperture of anywhere around f8- f20 depending on lighting, distance and size of the object.
For smaller objects, without too much gradient in depth, I would use between f8 and f20.
For objects with a bit more gradient, I would use between f14 and f20 I guess.
But even for something as small as a common garden snail moving toward the lens, f29 still doesn't work to capture the entire depth, or even half of the snail.

I think stacking may be my only option, provided of course, that the snail doesn't move too fast

sharpshot · « **Reply #6 on:** April 01, 2009, 04:59 »

Quote from: Chris.Alleaume on April 01, 2009, 04:33

Quote from: sharpshot on April 01, 2009, 04:19
Usually there just isn't much DOF with macro. Using a tiny aperture might help a bit but then the lens can produce softer looking photos. You could try focus stacking with non-moving objects. I tried combineZP, it is free and works quite well. For moving objects, a ring flash might help.

Sometimes shallow focus can look good but a few of the sites reject them, perhaps because the reviewers don't know enough about macro photography.

Thanks, sharpshot,
I considered that possibility, that perhaps some reviewers don't know enough about Macro photography.
I guess I could try focus stacking for non-moving objects - not a bad idea at all.

Just a question though - how would a ring flash help with DOF on moving objects?

It should give you more light, so you can use a faster shutter speed to freeze the movement and keep a small aperture to maximize DOF without having to use higher ISO. I haven't used one for about 10 years but I have read that insect photographers find them useful.

RaFaLe · « **Reply #7 on:** April 01, 2009, 05:18 »

Awesome! Thanks for that - I'm going to try find one and give it a try.
It actually makes good sense!

Chris

alias · « **Reply #8 on:** April 01, 2009, 05:50 »

Online depth of field calculators such as DOF Master are great for reminding us that depth of field gets shorter and shorter, the closer the point of focus such that reducing the size of the aperture will have very little effect other than to reduce sharpness.

For example:

Using a 1.6x crop camera focused at 100mm using a 90mm lens at f/2.8 the depth of field is (more or less) zero.

At f/8 the depth of field is still (more or less) negligible (appx zero).

At f/16 the depth of field is still (more or less) negligible (appx 0.1 mm according to the calculator)

MacphersonPhoto · « **Reply #9 on:** April 01, 2009, 06:21 »

Depth of field at 1:1 magnification (true macro) is tiny. As alias says, usually less than a 1mm. And the longer the focal length of the lens, the smaller depth of field is anyway (I don't know if this also applies to the virtual focal length created by the crop factor).
One way to improve it, where it is feasible to do it, is to shoot the subject at an angle that maximises the amount of the subject that is within the focal plane. i.e. if you shoot a flat leaf from above, with your camera parallel to the leaf surface, you will obviously have more in focus than if you shoot it at an angle to the camera. (This can be tricky with moving subjects, obviously! And with subjects that are not relatively flat, where you just have to choose what you want in focus.)

Are you using autofocus? With extreme close-ups it is usually better to focus manually, to make sure you get the focus where you want it. (Though that doesn't change the depth of field.

dirkr · « **Reply #10 on:** April 01, 2009, 06:34 »

One way to increase DOF would be to buy a T&S lens.
see http://en.wikipedia.org/wiki/Tilt-shift_photography

RT · « **Reply #11 on:** April 01, 2009, 06:35 »

Quote from: Chris.Alleaume on April 01, 2009, 04:07

Something else I can try for increased DOF?

Have a look at the Canon 90mm TS-E lens

RaFaLe · « **Reply #12 on:** April 01, 2009, 07:23 »

Quote from: MacphersonPhoto on April 01, 2009, 06:21

Depth of field at 1:1 magnification (true macro) is tiny. As alias says, usually less than a 1mm. And the longer the focal length of the lens, the smaller depth of field is anyway (I don't know if this also applies to the virtual focal length created by the crop factor).
One way to improve it, where it is feasible to do it, is to shoot the subject at an angle that maximises the amount of the subject that is within the focal plane. i.e. if you shoot a flat leaf from above, with your camera parallel to the leaf surface, you will obviously have more in focus than if you shoot it at an angle to the camera. (This can be tricky with moving subjects, obviously! And with subjects that are not relatively flat, where you just have to choose what you want in focus.)

Are you using autofocus? With extreme close-ups it is usually better to focus manually, to make sure you get the focus where you want it. (Though that doesn't change the depth of field.

I am using mostly manual focusing on macro shots. I find this to be a little more accurate, which also eliminates the slightest blur on recomposing.

rimglow · « **Reply #13 on:** April 01, 2009, 07:58 »

Well, I have a lot of experience shooting macro for stock images. I use the Canon 90mm TS-E lens, with my Canon Mark II 1Ds. I have shot most of the products, in my portfolio, at f.32, for years. You will find that you have to sharpen, somewhat, in post production, but it will give you maximum depth of field.
However, all that changed, with the latest version of Photoshop, CS4. Macro will never be the same, for static images, shot on a tripod. I now shoot at F.11 or f.16. I make 4 exposures. I first focus on the front of the subject, and make a mark on the side of the lens with a white pencil. Then I focus on the back, of the subject, and mark that, on the lens. Next, I make 2 marks, of equal distance between the first 2 marks. Go back to the first mark, and start shooting. One exposure, for each focusing mark. Open all 4 exposures, in Photoshop, and use the Auto Align, and Auto Blend features. Viola! Macro photography with sharp focus front to back.

PeterChigmaroff · « **Reply #14 on:** April 01, 2009, 12:35 »

One thing I know for sure is that micros, or those who act as reviewers for micros, don't understand selective focus. Or if they do understand it, they have a heavy dislike for it.

MatHayward · « **Reply #15 on:** April 01, 2009, 13:24 »

You've gotten some great advice here. I would also encourage you to experiment with a higher ISO. Try 800 or maybe even 1600 and run your file through noise reducing software like Noise Ninja or Neat Image. I use Neat Image personally and you would be surprised at the results you can achieve.

Good luck!

Mat

tan510jomast · « **Reply #16 on:** April 01, 2009, 16:11 »

Quote from: dirkr on April 01, 2009, 06:34

One way to increase DOF would be to buy a T&S lens.
see http://en.wikipedia.org/wiki/Tilt-shift_photography

ah yes, Scheimpflug principle. or used a camera like the Rolleiflex medium format that has bellows attachment so that you can move the lense while you keep the film plane parallel to the subject.
view camera theory 101

batman · « **Reply #17 on:** April 01, 2009, 16:24 »

Quote from: tan510jomast on April 01, 2009, 16:11

Quote from: dirkr on April 01, 2009, 06:34
One way to increase DOF would be to buy a T&S lens.
see http://en.wikipedia.org/wiki/Tilt-shift_photography

ah yes, Scheimpflug principle. or used a camera like the Rolleiflex medium format that has bellows attachment so that you can move the lense while you keep the film plane parallel to the subject.
view camera theory 101

also remember that the distance between focal plane and object plays a big part in DOF.ie. DOF shallows with proximity. so if you have a high MP camera, you could try shooting from farther back so you will have more play in DOF. then crop to get a usable image.
this is is cases where, like the moving snail, you cannot shoot several images
and layer them together .
of course you can try to oldest trick in the world, used by commercial macro photographers in the old days. ie. freeze the snail, as it moves slower when it's cold.
but that could be cruel if the poor snail dies .

RaFaLe · « **Reply #18 on:** April 02, 2009, 00:13 »

LOL!
No guys, I'm not going to be freezing anything

Thanks for the loads of excellent advice to all.
I'll be looking at my various options.

Turns out all of the hardware options are ridiculously expensive. Never thought a ring flash could cost as much as it does.
This is turning out to be a very expensive hobby...

Thanks again

RaFaLe · « **Reply #19 on:** April 03, 2009, 02:25 »

I gave this a bash yesterday.
I took about 10 frames of the same pictures.
Used Photoshop CS4 and uploaded the images into a stack.
Then used Auto-Merge to get the resulting in-focus image - it's absolutely AWESOME!

Thanks guys!!

Chris

tempura · « **Reply #20 on:** April 03, 2009, 06:48 »

Quote from: Chris.Alleaume on April 02, 2009, 00:13

LOL!

Turns out all of the hardware options are ridiculously expensive. Never thought a ring flash could cost as much as it does.
This is turning out to be a very expensive hobby...

Thanks again

http://www.flickr.com/groups/strobist/discuss/72157603473900857/?search=diy+ring+flash