dof difference between canon 100macro/180macro

[johnr1]

What is the difference in the depth of field between the canon 100mm macro and the canon 180mm

macro, using the same aperature and magnification? Example: if I'm shooting a small flower at 1:1 at f22,

will the 180mm give me less depth of field? If so, how much more would I need to stop down the 180 to

attain the same depth of field at the same magnification that the 100mm produces? Thanks, John

[erik_loza]

It's not depth of field you're thinking of in this case, it's compression. All things being equal, if subject is composed identically through the viewfinder of a camera with a 100mm lens and a 200mm lens, you will see half the background in the longer lens, due to its narrower field of view. It doesn't have so much to do with working distance from the subject (though that also has it benefits), so much as being able to isolate the subject from background clutter that may not be what you want. I suppose that f16 on a 100mm lens might look a little different than f16 on a 200mm lens as I think about it, but that's not really much of an issue. Does this make sense?

[don_cooper]

Bob Atkins has a calculator here that might help - http://www.bobatkins.com/photography/technical/dofcalc.html

[dan_fromm2]

There is no difference.

[mendel_leisk]

There's a comparison here http://www.the-digital-picture.com/Reviews/Canon-EF-100mm-f-2.8-USM-Macro-Lens-Review.aspx

[jens_krause]

A 180mm macro lens will give the same depth of field (DOF) as a 100mm macro ? reproduction ratio, aperture, and sensor/film size being constant. For example, if you use a Canon 20D with both lenses at 1:1 reproduction ratio, and an f/8 aperture, depth of field is identical.

 

<p><a href="http://www.jckrause.com/">Jens</a>

[Two23]

All lenses have the same DOF at the same aperature.

 

--->DOF depends on (1) Image size (2) Aperature. NOT focal length.

 

 

Kent in SD

[Two23]

I forgot to add that if you start using aperatures like f22 and f32 on 35mm/digital lenses, the photo won't be as sharp as you might think. You start running smack into diffraction. But that's another topic.

 

 

Kent in SD

[johnr1]

So if I shoot an object that's 3" long and 1/2" diameter on a tabletop at 1:2 with both lenses,

there will not be anymore image fall off with the 180mm than the 100mm? They will look

equally in focus? The reason I'm asking is that I currently have the 100mm macro, and I

would like more room for lighting for tabletop macro panos, but not at the expense of the

subject losing apparent sharpness from the closest point to the farthest. I've been successful

attaining this effect with the 100mm. I'm using a 1ds mk2. Anyway, I'd like to be fairly certain

of the results before I purchase the 180mm. Thank all of you for your feedback. John

[g._armour_van_horn]

A 180mm lens will have shorter depth of focus at any given distance than a 100mm lens. All lenses have greater depth of focus the further from the camera you go. When the image is at the same size on the sensor, you've moved out with the 180 far enough that the depth of field at that distance is the same as it would have been with the 100 in closer.

 

Perhaps it would be clearer expressed this way. Say your 100 gives you two inches of depth of field at a range of 10 inches. Your 180 might give you 1.25" DOF at that range, but it will also give you a DOF of two inches at a range of 18 inches. By choosing the 180 you get exactly the same depth of field, but you get eight more inches of working distance and you narrow the angle of view so you have less background behind the subject.

 

When you get right down there, you might want to do some actual sharpness tests of different apertures. At some point the aperture (measured in diameter) causes diffraction which costs you sharpness. You could find that f/16 is sharper than f/22 at the sharpest point, although it will have less DOF. The longer lens will have a larger aperture diameter at any f-stop than the shorter lens, so if you find you are diffraction limited you will benefit again from the longer glass.

 

Van

[mendel_leisk]

Take a look at the comparisons in my above link. The focal length is a significant factor in the background appearance.

[johnr1]

Thanks everyone for your help , I understand. John

[Two23]

http://www.cybercollege.com/myths.htm

 

http://www.normankoren.com/Tutorials/MTF6.html

 

and best of all:

http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml

 

 

I've actually gone out and done the comparison shots myself twice. All lenses have the same DOF. By DOF, I mean the front to back distance of the area that is in sharp focus.

 

 

Kent in SD

[johnr1]

Great articles, Kent. I especially liked his definition of the circle of confusion. I bookmarked

the articles along with the info from Mendel and Don. You guys are great. Thanks again. John

[Hector Javkin]

If you have a serious problem with depth of field in macro photos (and who doesn't), and you're prepared to spend on a 180mm Canon macro, you might see if the adapter for Nikon lenses will work on the Nikon PC Micro 85mm f/2.8D, a tilt-shift lens. You can then use tilt to get much more of your image into focus. I know that Canon has some wonderful tilt-shift lenses, but I don't think they are designed for macro.

[michael_bradtke]

This is a nice little aplication that I have used for a few years. Works very well to figure out how your DOF is going to change when you change focal lengths.

Its free and it works very well. I first learned about this from a first AC that I was working with.

 

http://tangentsoft.net/fcalc/win32.html

 

To answer the question. Yes there is a difference between the 100 and the 180. It is not a lot but it will make a difference.

 

Michael

[johnr1]

Hi Hector, I have the canon 90ts-e and the 45ts-e lenses, and their minimum focusing

distances are about the same as the nikkor. The 45 is .4 meters, the 90 is.5 meters, the

nikkor is .39 meters. I do use these often when I want to control my plane of focus, with

remarkable results, but they don't fit this need. I designed and built a pano-macro table,

which allows me to shoot multiple images of small items, without parallex problems, stitch

them, and then make huge prints with no loss of detail, on my Epson 7800 pro. So I

usually shoot a single object, where the tilt function offers no advantage. I can only rely on

stopping down to increase my depth of field.

Michael: Thanks for the link, unfortunatly, none of the software will work on my Mac.

 

John

[michael_bradtke]

John

They do have a version for Mac

 

http://tangentsoft.net/fcalc/mac.html

 

A bunch of the AC's I work with have it on there Palm Pilots

 

Hope that this helps

[johnr1]

Hi Michael,

 

I tried installing the unix version earlier, and for some reason it won't install on my G5. The

other version is for an older operating system.

 

John

[bobatkins]

DOF will be the same, but distant background (and close foreground) blur will be different (more with the 180 macro at the same aperture).

 

DOF determines only what's in "acceptable focus" and says little about the out of focus areas.

 

See http://www.bobatkins.com/photography/technical/bokeh_background_blur.html for a calculator which will give you both DOF and background blur information.

 

For all practical purposes, DOF depends only on magnification and aperture when the subject distance is small compared to the hyperfocal distance. You may also need to take pupil magnification into account for significantly telephoto and retrofocus designs, but none of these considerations are usually very important when looking at "normal" macro lenses (50mm to 180mm in focal length).

 

The major effect of the focal length is the angle of view and so the width of the background that's included in the image.

[johnr1]

Thanks, Bob.

 

John