Depth of Field Help

DDR

Hi,
This is my first post so be gentle.
I am using a 10d and a 28-70 L.
I am taking photos that are off plain most of the time to get the effect I want.
The depth of field changes as the photo angle changes.
Is there a cure for the out of focus towards the back of the picture?
Here is an example..
As you can see the center is focused and the ends are not.
I think I took this at f16 100 iso with my mono flash set up.

GREAPER

It could just be me, but it doesn't look tack sharp anywhere to me.

To get the depth of feild deeper, you need a wider aperature, but f/16 is pretty wide already. Try a longer lens and step back a bit, this may help, just an idea.

DDR

Longer lens like?

fish

GREAPER wrote:

It could just be me, but it doesn't look tack sharp anywhere to me.

To get the depth of feild deeper, you need a wider aperature, but f/16 is pretty wide already. Try a longer lens and step back a bit, this may help, just an idea.

good advice. the 70mm is probably long enough. don't try to shoot a macro with it...step back.

DDR

fish wrote:

good advice. the 70mm is probably long enough. don't try to shoot a macro with it...step back.

Ok Ill do that for now with what I have.

What lens will allow me to take the shots like I want macro up close like the posted pic and get good results on long subjects at an angle?

wxwax

Are you sure that was shot at f16? I can see the foreground being blurry because your lens might be too close to the object. But at f16, the back end ought to be in focus.

How far was your lens from the object? And was this definitely shot at f16?

And I'll go the oppositie direction of the others: I reckon a wider angle lens might be what you need. You can get everything you want in the frame, no need to crop, and depth of field won't be a problem.

DDR

wxwax wrote:

Are you sure that was shot at f16? I can see the foreground being blurry because your lens might be too close to the object. But at f16, the back end ought to be in focus.

How far was your lens from the object? And was this definitely shot at f16?

And I'll go the oppositie direction of the others: I reckon a wider angle lens might be what you need. You can get everything you want in the frame, no
need to crop, and depth of field won't be a problem.

Sid, Thanks for the good ideas.
I was very close. (my fault) I am backing up more but not getting the effect i want.

After looking around I found some info on off plane shooting. The angle should be 20 - 24 degrees max. I was hoping there was a way to shoot at more of an angle and still retain focus on both ends.
What would happen with a wide angle lens?

Also I keep hearing view camera come up.

They dont make these digital do they?

wxwax

Now you're talking $$$$$

A wide angle lens would let you get the whole thing in the frame. But depending upon how wide you get, there might be some bending of the object. A tilt/shift lens would cure that, I believe. But again, we're talking $$$.

The other folks are suggesting you use a longer focal length and stand further back. That will work, but I suspect you'll also have a lot of empty too space to either crop or live with.

Shay Stephens

Like wxwax mentioned a tilt/shift lens would help. But if you are looking to do this with the tools at hand, then you will have to resort to some darkroom techniques. Focus blending, where you take at least two shots with different focus points and blend the sharpest portions of each photo into one should get you what you need.

So for example, take three shots from a tripod. The only thing that changes from shot to shot is the focus point. First shot with the closest portion in focus, the second photo with the middle in focus, nd the last focus on the rear of the subject.

Take those three shots and put them in layers. Erase or mask out the blurry portions of the top two layers. Once you flatten the image, you will have one photo with a wider DOF than you could get otherwise.

Something to try anyway ;-)

DDR wrote:

Sid, Thanks for the good ideas.
I was very close. (my fault) I am backing up more but not getting the effect i want.

After looking around I found some info on off plane shooting. The angle should be 20 - 24 degrees max. I was hoping there was a way to shoot at more of an angle and still retain focus on both ends.
What would happen with a wide angle lens?

Also I keep hearing view camera come up.

They dont make these digital do they?

wxwax

Shay, help me out here: is there a reason why the same effect couldn't be achieved using a super-small aperature? e.g. f22?

Shay Stephens

Doh! I had some really nice response going and I closed my browser by accident. So now I have try and remember what I was saying.
There are three things that have a big impact on the DOF of a shot. Focal length, distance from camera to subject, and aperture.

The smaller the focal length, the greater the DOF for the same focus distance. For example, if you are focused 10 feet away, a wide angle lens (28mm) will have a wider DOF than the same photo taken with a 200mm lens.

The farther away you focus, the greater the DOF.

The smaller the aperture, the larger the DOF. Using f/22 will give you greater DOF than using f/2.8

You can mix and match those variables to dial in what you want your photo to look like.

This is an example showing two of those variables changing (Focus distance and aperture)


In the first photo I am using the Canon 100mm f/2.8 macro lens. A side point, a good macro lens allows you to get farther away from the subject, not closer. So back to the first image, the camera lens was about 6 inches away (the 1:1 magnification distance) from the tape measure and you can see that the DOF is about an inch deep.

Now in the second photo, the only thing that has changed is the focus distance. It is farther away, and look at the increase in the DOF.

By contrast, with everything else being the same, the aperture is changed from f/22 to f/2.8 and you can see that the DOF shrinks again to about an inch. With this lens I could go down to f/32 if I wanted.

That being said, if all else fails and one just can't get the DOF the way they need it, focus blending is always an option to consider. Though I would consider it the last option to consider.

wxwax wrote:

Shay, help me out here: is there a reason why the same effect couldn't be achieved using a super-small aperature? e.g. f22?

wxwax

What a great post! Thanks for taking the time to shoot and write it. I hadn't really considered the impact of distance to subject wrt depth-of-field.

fish

wxwax wrote:

What a great post! Thanks for taking the time to shoot and write it. I hadn't really considered the impact of distance to subject wrt depth-of-field.

Shay, we're extremely fortunate to you as a resource on dgrin. Your contributions have not been insignificant, and I'm sure I'm not alone when expressing my gratitude for sharing your extensive knowledge.

You rock.

DoctorIt

Nice one Shay!

I've tried to take a run of sample shots showing DOF differences... I can't believe it never occured to me to do it with a tape measure!!! I'm an engineer, really!

:uhoh

Shay Stephens

hehehehe, I know what you mean DoctorIt.

Fish and wxwax, thank you

DoctorIt wrote:

Nice one Shay!

I've tried to take a run of sample shots showing DOF differences... I can't believe it never occured to me to do it with a tape measure!!! I'm an engineer, really!

:uhoh

DDR

Shay,

Thanks for the great educational demo.

Ok I am using a 28-70 mm 2.8 L lens.

The size of my subjects are 8-16 inches long.

What Lens would allow me to fantastic close up and very clean full shots of these SHINY objects. The problems is that I have found that stop settings for these objects are best at f13-f19 So I cannot stop the lens down more. If I try to shoot with more light I get burn spots.

I can stop the lights up and down but it just seems the higher the stop the more light bounce and burn spots I have to contend with.

Shay Stephens

Assuming f/16 and a 16 inch subject.

At 24mm you are about 16 inches away and calculated DOF is 2.5".
At 70mm you are about 5 feet away and calculated DOF is 4 inches.

However, the calculations don't tell the whole story. I set the camera up at 5 feet and 70mm lens so that a 16" object would be visible in the frame. I set a tape measure to show one foot in front and one foot behind the focus point. At f/16, the whole thing looks plenty sharp to me (this is a resized crop):




And a reminder to those who don't know it, but when shooting shiny objects, you are not shooting the object, but the reflections. Adjust your lighting and surroundings so that those reflections look good "in the mirror".

DDR wrote:

Ok I am using a 28-70 mm 2.8 L lens.

The size of my subjects are 8-16 inches long.

What Lens would allow me to fantastic close up and very clean full shots of these SHINY objects. The problems is that I have found that stop settings for these objects are best at f13-f19 So I cannot stop the lens down more. If I try to shoot with more light I get burn spots.

I can stop the lights up and down but it just seems the higher the stop the more light bounce and burn spots I have to contend with.

Shay Stephens

I just did a test comparing the 16-35mm f/2.8 lens, the 100mm f/2.8 macro, and the 70-200mm f/2.8 lens. The best results were from the 100 mm macro. It gave the best working distance (2'2") and image size. If you are doing a lot of product work you would do well to include the lens in your kit.

Here is a shot similar to the one you posted. I focused on the center of the knife and used f/16 with the 100mm macro from 2'2" away. Resized to 550 wide and sharpened with unsharp mask (100%, .5, 0):



If I zoom in 100% the ends of the knife start to loose sharpness. I could get a wider DOF, up to f/32 on the 100mm macro. If critical focus at f/16 were important, I would do focus blending. I would take two more photos, one focused on the close end and one on the far end. Then take those photos and stack them into layers and align them, then mask out the blurry parts like this:



And this is the resulting photo resized to 550 wide and unsharp mask (100%, .5, 0)



Not a huge difference in sharpness on screen or the typical print, but if you intend on printing very large, every little bit may help. It's not a cure-all, but good to know how to do in a pinch.

wxwax

I see a big difference, esp. in the handle. Great stuff, Shay.

DDR

Shay,

Nice shot!

You have done this before I'll bet. The 100 mm looks very clean. Thanks for the lesson on blending also.

I read something about plane angle to the work piece somewhere. they said 20-24 degree max .

Is that a good number?

Shay Stephens

I don't know the numbers for that, but the closer you can get the piece to perpendicular to the lens axis the better for sharpness. 20-24 degrees sounds like it would be a good number.

As far as product photography, I don't advertise for it anymore, but I still do some for local artists and other businesses. Going to be doing some food shots this month.

This is a post card a local furniture maker is using that has my work.

DDR wrote:

Shay,

Nice shot!

You have done this before I'll bet. The 100 mm looks very clean. Thanks for the lesson on blending also.

I read something about plane angle to the work piece somewhere. they said 20-24 degree max .

Is that a good number?

Jekyll & Hyde

DDR wrote:

The problems is that I have found that stop settings for these objects are best at f13-f19 So I cannot stop the lens down more. If I try to shoot with more light I get burn spots.

I can stop the lights up and down but it just seems the higher the stop the more light bounce and burn spots I have to contend with.

J: I'll leave the aperture and DOF lesson to Shay (BTW really nice demonstration).

H: But if you happen to win the Lottery, or triple your knife quota this year, look into getting one of these:
http://www.novoflex.com/english/html/fr_ema5.htm

J: The T/S with the ProShift+ Adapter would be right up your alley. Increase your DOF, increase your effective resolution, and decrease perspective induced distortion, all in one fell swoop.

H: I used to use Nikon's macro bellows back in the old film SLR days, and after using tilt/shift for a shoot, you'll ask yourself "how did I ever get along without it?"

J: As for lighting, I'd recommend using hot lights. I know it's not as sexy as flash, but your images will really show a lot of improvement as you can make minute adjustments to the lighting strength, angle, and coverage and see the effect immediately.

H: To help attenuate those hot spots, use a polarizer and a large diffuser. Also, one of the problems you are having as you increase the light intensity, is that you are in effect increasing the dynamic range of the lighting (basically the light ratio). Because it's such a reflective object, some of the surfaces will reflect 100% of the light to the camera (no matter the intensity setting), and others will always reflect almost zero.

J: The key is to find the minimum light intensity that will still give you the full dynamic range you desire in the shot. I think you've come to this conclusion already, so I just include it for the benefit of all.

H: Hope this helps some, and hope you sell tons of knives.
J&H

wxwax

Good stuff, Hyde, much better than Jeckyll's rot.

nzmacro

With smaller objects we can take 2-3 shots at varying focus points and then combine them with software. Old trick that still works well IMO.


Danny.