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DPChallenge Forums >> Tips, Tricks, and Q&A >> DOF and supplementary lenses
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06/21/2002 05:35:19 AM · #1
There's been some discussion here and there on these forums about depth of field (DOF). Basically a lot of digital cameras have a problem limiting DOF - pretty well everything from the subject to infinity is in focus. I've seen this spoil some great shots in the challenges because you end up with a cluttered background when blurry would look better. The "classic" way to deal with this is to Gaussian Blur the background but, as we all know, that's not allowed here.
It occurs to me that if you use a supplementary lens (like a magnifying glass or slide loupe (or a dedicated close up lens)) it should dramatically reduce the DOF since the camera can no longer focus on infinity. I know this has been suggested for macros but has anyone tried it for regular shots to limit the DOF?
06/21/2002 08:33:30 AM · #2
I have not tried that, per se. But since you did mention slide loupes, I took an interesting picture with a large 5x loupe yesterday. check it out, lol .. I had never in my life seen a slide loupe that big, but then i saw one of the interns using it to examine nitrate negatives, got all excited.
06/21/2002 09:50:36 AM · #3
In reality, the ONLY thing that affects the depth of field of an image is the aperture size. The depth of field may be distorted with a lens attachment but the actual depth of field is not changed by any additional lens attachments.

I thought that I could increase the depth of field on my F707 by stopping down with a neutral density filter... I found out rather quickly that this wasn't the case... :)
06/21/2002 11:37:17 AM · #4
Depth of field is affected by f/stop, focal length, and focal distances. The closer that focal point is to a camera, the less the DOF (think about macro shots). Also, a longer lens with have less DOF at a given f/stop than a shorter lens (one reason why those dramatic landscapes with foreground and background in focus are shot with wide-agnle lenses). That is the problem with digital cameras. the LCD is so samll, that the lens' focal lenght is tiny. giving much greater DOF than 35mm.

Contax is the only camera maker I have heard of that uses a full 24x36mm LCD. This should have all the same lens characteristics as a 35mm film camera. Unfortunately it is $7000
06/21/2002 11:40:47 AM · #5
Originally posted by Zeissman:
Depth of field is affected by f/stop, focal length, and focal distances. The closer that focal point is to a camera, the less the DOF (think about macro shots). Also, a longer lens with have less DOF at a given f/stop than a shorter lens (one reason why those dramatic landscapes with foreground and background in focus are shot with wide-agnle lenses). That is the problem with digital cameras. the LCD is so samll, that the lens' focal lenght is tiny. giving much greater DOF than 35mm.


Contax is the only camera maker I have heard of that uses a full 24x36mm LCD. This should have all the same lens characteristics as a 35mm film camera. Unfortunately it is $7000


This is interesting... I can't get nearly the depth of field with my F707 that I can with my Nikon N60. I *would* agree that F4 on a digital camera gives more depth of field than F4 on a film camera though.. I am limited to F8 on my F707 which seems to be approximately equivalent to F12 or so on my Nikon. The catch is that I can stop down to F22 with both of my lenses on the film camera and I can't get anywhere near that with the digital... :)
06/21/2002 12:05:10 PM · #6
nevermind

* This message has been edited by the author on 6/21/2002 12:15:15 PM.
06/21/2002 12:13:20 PM · #7
Originally posted by Zeissman:
I do not know the specs on the N60, but I would guess it has a smaller CCD than the F707. Check the multiplication factor between actual lens size, and 35mm equivilant. The F707 is about 3.9x. Some of the Nikon cool pics are 6.5x. The larger the multiplier, the smaller the CCD or CMOS sensor.


The image sensor on the N60 is 24 X 36mm ;))
06/21/2002 12:14:38 PM · #8
N60 is a film camera? I have never bothered with Nikons

Originally posted by Jonniboy:
Originally posted by Zeissman:
[i]I do not know the specs on the N60, but I would guess it has a smaller CCD than the F707. Check the multiplication factor between actual lens size, and 35mm equivilant. The F707 is about 3.9x. Some of the Nikon cool pics are 6.5x. The larger the multiplier, the smaller the CCD or CMOS sensor.


The image sensor on the N60 is 24 X 36mm ;))
[/i]


06/21/2002 12:33:13 PM · #9
The N60 is a 35mm SLR film camera...
06/21/2002 12:35:05 PM · #10
Originally posted by Jonniboy:

The image sensor on the N60 is 24 X 36mm ;))


Problem is you have to use a new sensor for each shot. Good thing they come in convenient 24-packs.

-Terry
06/21/2002 12:36:23 PM · #11
I sometimes get the economy 36 pack for those long nites...
06/21/2002 01:03:30 PM · #12
Originally posted by Zeissman:
Depth of field is affected by f/stop, focal length, and focal distances. The closer that focal point is to a camera, the less the DOF (think about macro shots). Also, a longer lens with have less DOF at a given f/stop than a shorter lens (one reason why those dramatic landscapes with foreground and background in focus are shot with wide-agnle lenses). That is the problem with digital cameras. the LCD is so samll, that the lens' focal lenght is tiny. giving much greater DOF than 35mm.

Contax is the only camera maker I have heard of that uses a full 24x36mm LCD. This should have all the same lens characteristics as a 35mm film camera. Unfortunately it is $7000

Also unfortunately the Contax isn't shipping yet. It's been delayed so long most everyone's giving up on it. The biggest benefit of its large sensor would be to give better wide angle. On my D1 the effective focal leingth of the lens is 1.5 times that listed. This turns my 28-120 into a 42-180. If you do a lot of wide angle work, digital will drive you crazy.

As for DOF in digital cameras, if look at some of the film point-and-shoots you'll see they have the same problem. When the apature and shutter are controled by the same part it seems to limit DOF control. DPReview.com gives examples of DOF adjustments in it's reviews, and I think steves-digicams.com does too. Unfortunatly, if you want traditional DOF control you have to use a SLR and 'traditional' lenses. Maybe that'd be a good excuse to get that D60 or D100.

On the topic of aux. lenses, I have the 1.5x telextender for my G2 and I find it compresses DOF a little. It makes the G2 a much better portrait camera for that reason and the focal leingth (about 150mm) works better also.

06/21/2002 01:56:38 PM · #13
I do not think I understand you point about shutter and aperature controlling the same part.

Controllability of a point and shoot is not the same as an SLR, becuase you cannot set it manually, but with digital, even if you can set it manually, DOF greater.

A if I set my camera to it highest zoom setting (90MM 35 equiv). and set the f/stop to 2.8, it will give much more DOF than my 90mm Tamaron lens. And that has to do with optics, not what controls f/stop.

The larger sensor on the contax give plenty of benefits, including increased image resolution (lines/mm) and lens performance. BHphoto has the Contax on it's web page, but it is not taking orders yet.

I have a Contax AX, and I hope that the Contax digital will fall into an affordable range in the next year.


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