The affect of F stop on DOF with a 100mm macro

Stan

I am trying to understand the EF100mm non USM macro lens, so I have been shooting at 1:1, the closest focal point and closing the apperture down to see the change in DOF these were all shot at iso 400

f/2.8

the pin has a curve across the top and a line on the bottom of the frame which are in focus.

As the f/ stop icreases, so the DOF increases only by far less than I had anticipated

f/4


f/5.6


f/8


f/11


f/16


f/20


The lens is as I hope I have shown stunning, but it will take a while to understand fully.

If anyone has any more input I would be interested to hear

Thanks
Stan

gus

Nice show stan

wxwax

Stan, how far away was the lens?

Stan

wxwax wrote:

Stan, how far away was the lens?

The lens says 1.007 ft, so that's from the sensor, the end of the lens is about 3 1/2 inches away In English that's 0.307m and about 85mm

wxwax

Stan wrote:

The lens says 1.007 ft, so that's from the sensor, the end of the lens is about 3 1/2 inches away In English that's 0.307m and about 85mm

Thanks.

DJ-S1

Stan, what's the diameter of the top of the pin? Looks tiny.

Stan

wxwax wrote:

Thanks.

Sorry Wxwax, I'm rushing, its lunch time.

here is a link to the original f/22 shot, cut down to Jpeg 1.8mb
http://stan.smugmug.com/photos/20033620-O.jpg

DJ-S1: about 1cm, or 10 mm or 3/8ths of an inch

pathfinder

Stan wrote:

Sorry Wxwax, I'm rushing, its lunch time.

here is a link to the original f/22 shot, cut down to Jpeg 1.8mb
http://stan.smugmug.com/photos/20033620-O.jpg

DJ-S1: about 1cm, or 10 mm or 3/8ths of an inch

10mm DOF at 1:1 - I'd say that is pretty good. Might get more DOF with a 50mm macro as the focal length is shorter.

Stan

pathfinder wrote:

10mm DOF at 1:1 - I'd say that is pretty good. Might get more DOF with a 50mm macro as the focal length is shorter.

tonight's lesson is DOF at say, f/8 or f/11, with local length between 1:1 and 1:4
maybe I'll never understand the lens fully but it is fun trying

wxwax

My only contrubition is to note that distance from lens to subject will have an impact on depth of field.

Stan

wxwax wrote:

My only contrubition is to note that distance from lens to subject will have an impact on depth of field.

Yes but how much, I have 2 calibration formulas, one excel format, the other a palm programme, but until i work on it for myself the theory is not as clear as the worked example

Khaos

When you are that close, forget about formulas. Use the smallest aperture you can. You've just answered all the questions you asked by posting this. You set up an environment and took pictures using various apertures. Use it for the future.

Lucky Hack

wxwax wrote:

My only contrubition is to note that distance from lens to subject will have an impact on depth of field.

Will it have more DOF when further away or the other way around?

Stan

Lucky Hack wrote:

Will it have more DOF when further away or the other way around?

Hi lucky, yes it has a greater DOF the longer the focal point, what I was not ready for was how much increase in DOF was possible by moving back a very short distance

Lucky Hack

Stan wrote:

Hi lucky, yes it has a greater DOF the longer the focal point, what I was not ready for was how much increase in DOF was possible by moving back a very short distance

Cool, Hey I forgot to mention, Great Series! Really cool, it's so rare that you see this kind of breakdown. We can talk about DOF and fstop & exposure and EV until blue in the face but to see a shot by shot comparison is really great! thanks again.

hoping this message finds you well -Ian

Stan

Lucky Hack wrote:

Cool, Hey I forgot to mention, Great Series! Really cool, it's so rare that you see this kind of breakdown. We can talk about DOF and fstop & exposure and EV until blue in the face but to see a shot by shot comparison is really great! thanks again.

hoping this message finds you well -Ian

Thanks, seeing is believing, everything else is theory. I was going to post the results but spent last night putting together the shots of the cheese grater... there are 8 focal points in the shot and not one is as sharp as I would like...

OH and because the front element moves, the frame changes too I think the USM has a fixed lens length, but am not sure.

I will post a selection of the 1:1 - 1:4 either here or on sumgmug soon

would you rather see a ruler (mm and old English) or the drawing pin?

PS If you are looking for info on the ability of the 100mm macro lens, don't look at me... this lens is awesome, in the reviews I have read, the USM is only as good in image (better in speed, noise etc) all I was interested in was getting to understand the mechanics of this lens. The F/stop is only a very small part of the options. The focus distance allows so much more DOF and increased sharpness, I am enjoying learning such a different dciscipline

stan

Lucky Hack

Stan wrote:

I will post a selection of the 1:1 - 1:4 either here or on sumgmug soon

would you rather see a ruler (mm and old English) or the drawing pin?

I know beggars can't be choosers, but how about both in the same shot?
If not, I'd prefer the drawing pin. Thanks

hoping this message finds you well -Ian

Stan

Lucky Hack wrote:

I know beggars can't be choosers, but how about both in the same shot?
If not, I'd prefer the drawing pin. Thanks

hoping this message finds you well -Ian

Ok interesting, given that the drawing pin is in the air and the tape is on the surface, and the point of origin of the focal point is the camera not the end of the lens. This will give two focus points in the DOF, in a full frame image, as with the first set of shots the DOF increased from the bottom of the shot.

This given, I will need to calibrate the shot with the tape to give the DOF from the sensor, unless I lay a measure down just to give the dof in the shot rather than giving the distance to the object....

Lucky Hack

Stan wrote:

Ok interesting, given that the drawing pin is in the air and the tape is on the surface, and the point of origin of the focal point is the camera not the end of the lens. This will give two focus points in the DOF, in a full frame image, as with the first set of shots the DOF increased from the bottom of the shot.

This given, I will need to calibrate the shot with the tape to give the DOF from the sensor, unless I lay a measure down just to give the dof in the shot rather than giving the distance to the object....

I can only bow in awe to your superior understanding of the subject matter.

hoping this message finds you well -Ian

ginger_55

I assume there is a preview thing on the 20D. Does it work well?

I will look for it, I mean look in the manual and try using it. When I shot film I used it all the time those many years ago. Now I just wing it. If I have to have a shutter speed, to take the shot, I have to have it. If I want a small DOF, I use small numbers, on my lenses that is 5.6, 8, stuff like that. If I want a large DOF, I have to worry about the shutter speed, but I take the numbers as high as I can and still not worry about shake, or put it on a tripod (not me, but someone else might).

Or like the other day, I get everything else right and totally forget the DOF and screw up the shutter speed in 50 shots or the DOF in another 10 shots. I am getting there, though. On my checkpoint list, that might be the last thing I am on as far as remembering to check it out. Or I may never remember it all. I did get it all right on more shots than I got one thing wrong.

Find out if you have a preview button, it is not that good, but better than nothing, if I remember correctly. Like with that macro, I would bracket or something, there is no leeway there.

g

tmlphoto

The preview button can be helpful, but you must learn to see the focus in a much darker viewfinder. I have been reading about nature macro some lately. Much of the 1:1 work is done at f/11 - f/16. The larger apertures don't give enough DOF (unless your going for the very limited DOF look) and the smaller apertures, while increasing DOF can start to introduce artifacts to the image related to the very small size of the aperture causing some diffraction of light under those conditions.

Ric Grupe

Stan...
...after reading your post, I happened on this article at Digital Outback Photo:

http://www.outbackphoto.com/workflow/wf_72/essay.html

I thought you might be interested.

ginger_55

Along with the other lenses I wish I had, that 100 macro is another one. I don't have a macro lens, so I am dealing with larger distances, usually kids, dogs, birds, etc.

That was interesting Thomas about the artifacts, that I did not know, is that also true of say birds, big birds, dogs, kids and things further away than macro?
Fence posts or trees would be a good example of something I would play with the depth of field on. I looked at that article. I don't think I really want macro bad enough to study it, use tripods, etc.


ginger

Stan

Ric Grupe wrote:

...after reading your post, I happened on this article at Digital Outback Photo:

http://www.outbackphoto.com/workflow/wf_72/essay.html

I thought you might be interested.

Thanks Ric

tmlphoto wrote:

The larger apertures don't give enough DOF

This is 1:1 @f/2.8 the focal length is 0.307m 1.007 ft

Stan

and 1:1 @f/11

tmlphoto

ginger_55 wrote:

Along with the other lenses I wish I had, that 100 macro is another one. I don't have a macro lens, so I am dealing with larger distances, usually kids, dogs, birds, etc.

That was interesting Thomas about the artifacts, that I did not know, is that also true of say birds, big birds, dogs, kids and things further away than macro?
Fence posts or trees would be a good example of something I would play with the depth of field on. I looked at that article. I don't think I really want macro bad enough to study it, use tripods, etc.


ginger

Ginger, the 100mm macro is a great lens. Not too expensive either. I use it for macro and for portraits. Its nice and light weight as well. I'm not sure about the artifacts at very small apertures for normal working distances. I think that they are present, but not to the degree seen with extream closeup work.

tmlphoto

Stan wrote:

and 1:1 @f/11

Stan, thats a couple of great demonstration shots. The DOF at f/11 is still pretty limited.

tmlphoto

Here is one of my early shots with the 100mm macro. Not too good. Talk about limited DOF. I'm not sure what f/stop , but it obviously wasn't enough. I have seen some nice photos that exploited an extream limited DOF to good advantage. Unfortunately, this is not one of them:): . f/3.5 1/60 ISO 800


This one turned out a little better. f/2.8 1/90 ISO 400


These show how much more DOF you get by backing up a little. They also show the difficuly of natural light macro with active subjects. I was on the edge of everything (shutter speed, ISO, f/stop) I'm ready to invest in a macro flash soon.

Stan

tmlphoto wrote:

Here is one of my early shots with the 100mm macro. Not too good. Talk about limited DOF. I'm not sure what f/stop , but it obviously wasn't enough. I have seen some nice photos that exploited an extream limited DOF to good advantage. Unfortunately, this is not one of them:): .

This one turned out a little better. f/2.8 1/90 ISO 400


These show how much more DOF you get by backing up a little. They also show the difficuly of natural light macro with active subjects. I was on the edge of everything (shutter speed, ISO, f/stop) I'm ready to invest in a macro flash soon.

Wow that's nice, EXiF does not record the focal length, but the DOF has increased dramatically even at f/2.8 by sepping back a little.

1:4 magnification is only 1.877ft (0.572m) focal lenght so it is not even a step back