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Archive 2007 · interesting focal length/DOF sample
  
 
Daniel Buck
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p.2 #1 · interesting focal length/DOF sample


DrPablo wrote:
...I'm not sure how far from th car he was...

about 1.5 meters. you can see where I had the tripod placed in the images on the 2nd page



Jun 13, 2007 at 06:01 PM
pere marti
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p.2 #2 · interesting focal length/DOF sample


DrPablo wrote:
...I mean the format size/CoC, focal length, aperture, and subject distance would be the same...

...The f/number shouldn't need to be scaled if you're using an 85mm lens on 4x5, though. The difference between a 4x5 lens and a 35mm lens is mainly the image plane coverage, but for a given focal length the f/stop and focal length don't change....


Aperture and f-number are not the same. Aperture = focal lenght / f-number. So, if focal length is scaled, so is f-number.



Jun 13, 2007 at 06:34 PM
DrPablo
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p.2 #3 · interesting focal length/DOF sample


I don't know if you're correcting me because you think I really don't know these things, or if you're splitting hairs. But strictly speaking, you've also been imprecise about aperture in what you've just said, because what you've just called aperture is really the diameter of the aperture pupil.

Aperture, strictly speaking, is an area and not a diameter. Because it's the area of the aperture opening that directly determines exposure. Diameter, which is divided into focal length to determine f/stop, is a derivative of aperture area. And this is why f/numbers progress by square roots of 2.

So if you really want to be precise about what aperture means, you should go around the forums telling people to only talk about aperture in mm^2 instead of in f/numbers.

But for practical purposes, the f/number is the single most useful statement of aperture that exists for photographers. It is a measurement of aperture that controls for focal length, making it universally applicable to all lenses. I can't think of any situation other than building a lens or a pinhole camera in which it's practically useful to think about the diameter or area of the aperture pupil.




Edited by DrPablo on Jun 13, 2007 at 02:07 PM GMT



Jun 13, 2007 at 06:54 PM
pere marti
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p.2 #4 · interesting focal length/DOF sample


DrPablo wrote:
...The LF lenses have a different amount of field curvature as well, depending on design, because they're often a fairly simple symmetrical or near symmetrical design. On the other hand, the stitched 85mm image on SF would be pretty darn flat if you could avoid parallax errors...


Curvature of field in lenses that are suposed to be rectilinear is a defect. But it is not what I was talking about. Imagine 3 shot are taken in a raw in order to stitch them. Their planes of focus are not on the same plane. The ones on the sides are slanted inwards. This was what I meant when I said (segmented) curvature of plane of focus.



Jun 13, 2007 at 07:05 PM
DrPablo
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p.2 #5 · interesting focal length/DOF sample


His images were not necessarily slanted inward. If you use a shift lens, or if you use a bracket that allows parallel shifting, there is no rotation about a central nodal point. Thus, the plane of focus can remain unchanged depending on technique.

pere marti wrote:
Curvature of field in lenses that are suposed to be rectilinear is a defect.


It's a lot more complicated than that, and I don't think that's a fair generalization. Very few rectilinear lenses are corrected to be perfectly flat at all focus distances, and that is by design. Curvature of field tends to be only completely corrected when close to infinity focus. The only lenses that are actually designed to have truly flat fields of view are copy lenses and some higher end macro lenses -- but their field is only perfectly flat at very close focusing distances. And this is most likely to be the case in lenses with symmetrical designs, of which there really aren't all that many.



Jun 13, 2007 at 07:13 PM
pere marti
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p.2 #6 · interesting focal length/DOF sample


DrPablo,

No need to be rude. You haven't understood me. About aperture and scaling both f-number and focal lenth to achieve comparable DOF, see here:
http://www.luminous-landscape.com/essays/Equivalent-Lenses.shtml
For sure Mr Charles Sidney explains better than me.

His images were not necessarily slanted inward...

Not necessarily, but they were (at least for the description he made and for the interesting "wrapping" effect of the blurring).



Jun 13, 2007 at 08:06 PM
Daniel Buck
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p.2 #7 · interesting focal length/DOF sample


hm... maybe we should lighten this discussion a bit, I didn't intend it to be so heated :-) Interesting read though, just don't want it to get personal with anyone!


DrPablo wrote:
His images were not necessarily slanted inward. If you use a shift lens, or if you use a bracket that allows parallel shifting, there is no rotation about a central nodal point. Thus, the plane of focus can remain unchanged depending on technique.


The camera was fixed on the ball head, no correction for parallax or shifting around of the camera (and obviously, no lens shifting!), just simple rotation (horizontal and vertical) of the camera on the ball head. However, the camera was angled downward for just about all of the shots (as much as probably 60 degrees!) but for the top row of images I'd say the camera was probably parallel with the horizon. (see the image of the tripod, notice how much higher the tripod is than the hood of the car) This creates kind of the 'sphere of focus', which is why none of the ground is in focus, because the focus area is so curved (due to the camera rotating all around?) the in-focus ground area is actually right at the base of the tripod, (maybe a few feet farther out).

The next one I do, I'll make sure to keep the in-focus ground area visible in the photograph.



Jun 13, 2007 at 09:01 PM
Daniel Buck
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p.2 #8 · interesting focal length/DOF sample


Finally got out to shoot some 'woods' (not the type of woods I was hoping for, but the test worked just fine, no problems stitching!)

Since I was with a group of people, I didn't want to hold them up from hiking, so I only shot about 4 images per stitch. The DOF will get thinner next time, and a wider field of view!

I was wondering how the forest areas would stitch (alot of messy details for the stitching software to possibly get confused with?) but I had absolutely no problems!

Another problem with this setting, the path I was shooting is actually much wider than it looks, it's wide enough for two people to walk side by side. First stitch was taken standing up, 2nd was taken crouched down, but focused much farther away.

Next time I hope to shoot a forest area with large thick trees that give more a sense of scale (which will make for a more confusing/odd image!)















Jun 17, 2007 at 04:09 AM
nikt
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p.2 #9 · interesting focal length/DOF sample


I must admit that is very cool. Interesting idea, don't know if I've seen it done like that before.


Jun 17, 2007 at 06:23 AM
Daniel Buck
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p.2 #10 · interesting focal length/DOF sample


nikt wrote:
I must admit that is very cool. Interesting idea, don't know if I've seenit done like that before.

I have been wondering this myself? I doubt this could have been done in the film days, so it would have to be done sometime in the past 5 years or so. I have done a bit of searching around, but haven't found anything particularly like this. Only a mention that when stitching things (for the purpose of more resolution) apertures need to be closed smaller to keep the same DOF.



Jun 17, 2007 at 06:28 AM
 

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Graham Mitchell
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p.2 #11 · interesting focal length/DOF sample


Daniel, this is one of the most inspirational threads I've seen in a long time. Great stuff and I can't wait to try it out as well.


Jun 17, 2007 at 08:35 AM
carstenw
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p.2 #12 · interesting focal length/DOF sample


Very cool technique. I have been wanting to do something similar for a long time, but never got around to it. Now you've set my arse on fire What stitching program do you use?

By the way, the version which is getting printed looks a little green. Is that on purpose?




Jun 17, 2007 at 10:00 AM
pere marti
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p.2 #13 · interesting focal length/DOF sample


Really interesting and worth exploring. Nice tunneling effect, specially the 2nd one, although I don't like the colors/lighting (I understand they are test shots). There are countless possibilities playing with the field of view and degree of overlapping.


Jun 17, 2007 at 12:19 PM
DrPablo
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p.2 #14 · interesting focal length/DOF sample


Daniel Buck wrote:
I have been wondering this myself? I doubt this could have been done in the film days, so it would have to be done sometime in the past 5 years or so. I have done a bit of searching around, but haven't found anything particularly like this. Only a mention that when stitching things (for the purpose of more resolution) apertures need to be closed smaller to keep the same DOF.


Really really cool stuff.

It's perhaps a little different, but this can be done with film. With LF even wide angle lenses have a very shallow DOF -- like a 150mm lens is a super-wide on 8x10 (comparable to around 20mm on full frame 35mm or 12.5 on APS-C). So you can indeed get a razor thin DOF with a wide angle.

You can also do it using extreme camera or lens movements if you have a tilt-shift lens or a view camera with movements. Like this one of mine that I captured on 4x5.








Jun 17, 2007 at 01:18 PM
Daniel Buck
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p.2 #15 · interesting focal length/DOF sample


DrPablo wrote:
It's perhaps a little different, but this can be done with film. With LF even wide angle lenses have a very shallow DOF -- like a 150mm lens is a super-wide on 8x10 (comparable to around 20mm on full frame 35mm or 12.5 on APS-C). So you can indeed get a razor thin DOF with a wide angle.

You can also do it using extreme camera or lens movements if you have a tilt-shift lens or a view camera with movements. Like this one of mine that I captured on 4x5.

I have seen thin DOF stuff with large format, but not very often. I was referring to the stitching aspect (when I said can't really be done with film). I have seen the tilt-shift type 'DOF' as well, but that gives a different look.


carstenw wrote:
Very cool technique. I have been wanting to do something similar for a long time, but never got around to it. Now you've set my arse on fire What stitching program do you use?

By the way, the version which is getting printed looks a little green. Is that on purpose?

I use Autopano (autopano.net) and at work we use both autopano, stitcher, and ptgui

Yes, I played with the colors a bit before I sent it to print, put a bit of green in there



foto-z wrote:
Daniel, this is one of the most inspirational threads I've seen in a long time. Great stuff and I can't wait to try it out as well.

I look forward to seeing your results



I wonder, what should I refer to this technique as? "Thin DOF stitching" ?



Jun 17, 2007 at 03:41 PM
carstenw
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p.2 #16 · interesting focal length/DOF sample


Stitching for DOF?

It occurs to me that one can get the DOF effects of large format on any format for which there is at least one lens which gives the thin DOF desired, such as 35mm. Very cool.

I am happy to hear that you use Autopano. I have been playing with this program myself and was almost ready to buy. Now I certainly will. I just need to find the money I have made two large panoramas today with little DOF. I will try to stitch them and see how it goes.



Jun 17, 2007 at 03:57 PM
Daniel Buck
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p.2 #17 · interesting focal length/DOF sample


carstenw wrote:
Stitching for DOF?

It occurs to me that one can get the DOF effects of large format on any format for which there is at least one lens which gives the thin DOF desired, such as 35mm. Very cool.

I am happy to hear that you use Autopano. I have been playing with this program myself and was almost ready to buy. Now I certainly will. I just need to find the money I have made two large panoramas today with little DOF. I will try to stitch them and see how it goes.


Autopano is great! It's handled everything I've thrown at it! And Alexandre is very nice as well, has made the updates that I have requested, and many others as well in a very timely fashion! As soon as the demo version handled a stitch that no other program would (in 2 minutes, no less!) they had my money. That was before stitcher had it's 'auto stitch', I haven't done a comparison since then, however.

Look forward to seeing your results as well

I have done alot of stitching in the past back when I was shooting with a 1D (4mp!!) so I would always stitch for resolution. Alot of times I would use my 135mm and do a 4x4 grid, or 6x6 grid of images. I'll have to try shooting the 135 at f2.0 and see how that one works as well! It won't give quite a wide angle look though.



Jun 17, 2007 at 04:03 PM
Andi Dietrich
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p.2 #18 · interesting focal length/DOF sample


Daniel, like it a lot, made me remember a photographer from Switzerland I met once

http://www.gerardpetremand.ch/index.html




Jun 17, 2007 at 05:39 PM
carstenw
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p.2 #19 · interesting focal length/DOF sample


Here is my first attempt. I had a lot of trouble controlling Autopano. It seems to be missing some manual control options, and anyway, I just bought it today, so I am not so used to its tools. That's 36 shots with an M8 and a 50 Summilux Asph, at f/1.4, at about 1.5m.








Jun 18, 2007 at 12:29 AM
DrPablo
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p.2 #20 · interesting focal length/DOF sample


Daniel Buck wrote:
I was referring to the stitching aspect (when I said can't really be done with film).


People have been doing it with film since the 19th century. Not for DOF per se, but for juxtaposing different captures to create panoramas.

Now with Photoshop there are all kinds of possibilities for scanned film. I mean, rather than buying a $6000 Fotoman panoramic 6x17 camera, I could just take three lateral captures with my 6x6 and stitch them after scanning. I could also do that with my 8x10 to produce huge stitched images -- imagine taking a 3x3 set of 8x10 frames and stitching them to produce a 24x30 image that is 24x30 inches at capture size (and with the tiny DOF of the format -- my wide angle on 8x10 is a 300mm lens).

At any rate, that's not to argue for equivalence. I mean there are all kinds of possibilities for stitching with DSLRs and even point and shoot digitals that are worlds more convenient than on film. And you've certainly discovered a very distinctive technique that holds great creative promise!



Jun 18, 2007 at 12:53 AM
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