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12-24-2010, 01:06 PM   #31
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QuoteOriginally posted by macTak Quote
I will not bother to correct all of the misstatements here.
No, please do. I welcome correction.

Meanwhile, skipping out on the math, I turn to page 77 of my K20D manual, which a little DOF table. What it basically says:

Shallow DOF: wide aperture OR long focal length OR near subject distance
Deeper DOF: tight aperture OR short focal length OR far subject distance


Last edited by RioRico; 12-30-2010 at 12:08 PM.
12-24-2010, 01:16 PM   #32
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QuoteOriginally posted by RioRico Quote
Deeper DOF: tight aperture OR short focal length OR far subject distance
Therefore, the DA 35 macro shot at f11, further back, with a 25% crop, might result in a better image than shot close with no crop and a smaller aperture?
12-24-2010, 02:29 PM   #33
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QuoteOriginally posted by paperbag846 Quote
Therefore, the DA 35 macro shot at f11, further back, with a 25% crop, might result in a better image than shot close with no crop and a smaller aperture?
No. The white paper is your friend (cf. p. 7, 19 in particular). To put it simply, by cropping, you are enlarging the image and so the DOF (perhaps using the term here is a bit confusing, but it is correct) is reduced (for you are changing the value of the circle of confusion). For instance, if you take a typical picture (like the shoe of the OP) and display it quite small, everything looks in much better focus than when you look at the full size image, and again every looks in much better focus than when you look at a 100% crop. So you actually need that same (say) f22 aperature for the focus to look the same if you were shooting further back and cropping than if you were shooting at the proper distance with f22 anyway.

Last edited by macTak; 12-24-2010 at 02:34 PM.
12-24-2010, 02:58 PM   #34
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QuoteOriginally posted by RioRico Quote
No, pleas do. I welcome correction.

Meanwhile, skipping out on the math, I turn to page 77 of my K20D manual, which a little DOF table. What it basically says:

Shallow DOF: wide aperture OR long focal length OR near subject distance
Deeper DOF: tight aperture OR short focal length OR far subject distance
There is more to it than that (such as the circle of confusion), although that is okay as a simplification, but keep in mind that these are are all related (not simply OR's)--for that shoe, if you use a shorter focal lengh, you need a nearer subject distance to get the same image scale, and so those cancel each other out as to DOF.


Last edited by macTak; 12-24-2010 at 03:31 PM.
12-24-2010, 03:20 PM   #35
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QuoteOriginally posted by yperion Quote
3) Tilt/Sift lenses
I still donít think that will help me here. And the price is high! Thanks for the link d.bradley
This will alleviate your problem, inasfar as this is the reason why 4"x5" cameras, and also medium format cameras with tilt and shift attachments, have been popular for product photography, that the tilt and shift lets you manipulate the plane of focus so it is on the same diagonal as the subject, or close to it.
12-24-2010, 08:50 PM   #36
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Physics says that increasing focal length decreases DoF when DoF is large and has little effect when DoF is small.

I am sorry the following looks complex; I included the equation for those who want to understand the effect of focal length on DoF in some detail.

Here's the total DoF equation for non-macro conditions written in terms of C=Circle of Confusion, N=f-number, M=Magnification, and F=Focal length:

DoF=2CN/M^2/[1-{CN/(FM)}^2] Note: Hyperfocal conditions when FM=CN

When F is large, the CN/FM term in the denominator is small which increases the denominator thereby decreasing DoF. While larger F always means smaller DoF (all else being constant*) the effect is small when FM >> CN; ie. far from hyperfocal conditions.

For example, according to http://www.dofmaster.com/dofjs.html, a Pentax K-x at F2.8 with a 100mm lens focused at 10m has a DoF of 1.17m while a 25mm lens focused at 2.5m (same view in the viewfinder) has a DoF of 1.18m - a 1% difference.

Dave

*The DoF equation is written in terms of M for this discussion because M=constant means the the size of the image on the sensor is constant.

Last edited by newarts; 12-25-2010 at 07:22 AM.
12-28-2010, 01:59 AM   #37
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Tilt/Sift lens

After a little more search I found that the tilt/sift lens, suppose to be what Iím looking for, for best results regarding the more in focus and sharpens Depth of Field.

So the Shift faction fixes the perspective

Original normal picture(no shifting)


Shifted picture


And the Tilt faction altered the depth of field, either to reduce or to extend the depth of field

Extended DOF, f/4, image plane tilted so that we get more DOF


Shallow DOF, same aperture as before, just tilted to the other direction.
This gives you and effect of a really large aperture.



So if at f/4, this kind of lens, can produce these DOF, I suppose that in smaller aperture could, sharpens and resolution, be excellent.
Can we add something more?
12-28-2010, 05:43 AM   #38
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QuoteOriginally posted by yperion Quote
After a little more search I found that the tilt/sift lens, suppose to be what I’m looking for, for best results regarding the more in focus and sharpens Depth of Field.

So the Shift faction fixes the perspective

And the Tilt faction altered the depth of field, either to reduce or to extend the depth of field

So if at f/4, this kind of lens, can produce these DOF, I suppose that in smaller aperture could, sharpens and resolution, be excellent.
Can we add something more?
That the Tilt-lens would partially solve your problem has been written by several people above. But be aware:

Tilting DOES NOT increase DOF. It tilts the focal plane. The focal plane remains as thin/shallow as the chosen aperture dictates. So, if you photograph a shoe in a studio setting, tilting the lens is the first step, than you have to close down the lens to increase DOF.

The cheapest option would be one of the Ukrainian tilt-adapters combined with a short fl mdeium format lens (the 55mm Mamiya 645 is cheap and okay, for example).

Ben

12-28-2010, 05:55 PM   #39
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QuoteOriginally posted by Ben_Edict Quote
That the Tilt-lens would partially solve your problem has been written by several people above. But be aware:

Tilting DOES NOT increase DOF. It tilts the focal plane. The focal plane remains as thin/shallow as the chosen aperture dictates. So, if you photograph a shoe in a studio setting, tilting the lens is the first step, than you have to close down the lens to increase DOF.

The cheapest option would be one of the Ukrainian tilt-adapters combined with a short fl mdeium format lens (the 55mm Mamiya 645 is cheap and okay, for example).

Ben
Correct. It doesn't increase the DOF but enables you to get the most efficient use of that depth you have.

Be aware that the 35mm lens I linked previously is the shortest focal length available outside of Nikon and Canon mounts, and cheap compared to the canon used market prices at ~900 for a MKI lens, and $2200 for a new 24mm MKII t/s lens. I've not seen much wider than the 55mm you listed. It's a good option for wide angle if you don't want to go with a longer focal length and the medium format t/s adapters.
12-28-2010, 08:30 PM   #40
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QuoteOriginally posted by d.bradley Quote
Be aware that the 35mm lens I linked previously is the shortest focal length available outside of Nikon and Canon mounts, and cheap compared to the canon used market prices at ~900 for a MKI lens, and $2200 for a new 24mm MKII t/s lens.
A Pentax 28mm shifter just sold on eBay for ~GBP300, rather less than others currently listing for ~US$650-900. But those just shift, not tilt. Russian PK T/S's go from US$370-850 but they're 80mm. It is much cheaper to tilt the subject plane rather than the lens plane. All that is needed is a tripod and some elbow room.
12-29-2010, 06:29 AM   #41
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QuoteOriginally posted by RioRico Quote
A Pentax 28mm shifter just sold on eBay for ~GBP300, rather less than others currently listing for ~US$650-900. But those just shift, not tilt. Russian PK T/S's go from US$370-850 but they're 80mm. It is much cheaper to tilt the subject plane rather than the lens plane. All that is needed is a tripod and some elbow room.
But tilting the subject plane alone doesn't do anything. It is the same as just using another angle between camera and subject - aka tilting the tripod head. The tilt-lens enables Scheimpflug movements, which is a different thing, because you can choose the angles between lens plane, subject plane and focal plane freely.

THe Pentax 28mm shift is a great lens outside the studio. At very short distances it performes abysmal (at least in my own experience). As I wrote above, the cheapest rout to go is one of those Ukraininan tilt-adapters TILT adapter Pentacon 6 - for Pentax Contax M42, NEW bei eBay.de: Lens Accessories (endet 30.12.10 15:22:50 MEZ) combined with a cheap but good medium format lens - in this case perhaps a Pentacon/Zeiss Jena 55mm. And in the studio the shorter fl, you may reach, compared to the only readily available tilt-lenses in K-mount, is also of advantage.

Ben
12-29-2010, 08:03 AM   #42
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QuoteOriginally posted by yperion Quote
After a little more search I found that the tilt/sift lens, suppose to be what Iím looking for, for best results regarding the more in focus and sharpens Depth of Field.

So the Shift faction fixes the perspective

Original normal picture(no shifting)


Shifted picture


And the Tilt faction altered the depth of field, either to reduce or to extend the depth of field

Extended DOF, f/4, image plane tilted so that we get more DOF


Shallow DOF, same aperture as before, just tilted to the other direction.
This gives you and effect of a really large aperture.



So if at f/4, this kind of lens, can produce these DOF, I suppose that in smaller aperture could, sharpens and resolution, be excellent.
Can we add something more?
A lens with about an 8 degree tilt would allow you to focus on an entire 18" wide plane viewed at about 30 degrees ( 60 degrees with respect to vertical). The Depth of Field should be sufficient at reasonable f-number to include an entire shoe as in the original post in this thread.

The above is within the range of the Hartblei tilt adapters available on ebay and elsewhere for about $130USD. I have such an adapter and it works well. The Hartblei adapters use Pentacon Six lenses which are also available on ebay. I use a pretty good 65:3.5 MIR 38 which cost me about $65USD I think.

The relation between magnification, m, Plane of Focus Tilt (with respect to plane perpendicular), and Lens Tilt is:

Tan(Plane of Focus Tilt) = (1+1/m)Tan(Lens Tilt)

For example, if Lens_Tilt = 8 degrees, and Plane_of_Focus Tilt = 60 degrees, then m = sensor_width/scene_width = 1/11.3, which for a 1" wide sensor corresponds to a scene width of 11.3".

For large magnifications like in Macro photography, large tilt angles are required, hence a tilt bellows might be used.

Dave
12-29-2010, 08:36 AM   #43
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I just looked up the DOF numbers for a 50mm lens.
If I got it right;
- at f11 with a 5 foot distance from the object, the in focus area is 4' 4.9'' to 5' 9.2''
- at f8 the in focus area is 4' 6.8'' to 5' 6.2''
So I suspect a 50mm will do the "shoe" job with a little cropping in post processing
12-29-2010, 10:17 AM   #44
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QuoteOriginally posted by Ben_Edict Quote
The tilt-lens enables Scheimpflug movements, which is a different thing, because you can choose the angles between lens plane, subject plane and focal plane freely.
Indeed. But that requires a rather severe tilt, right? Do any Pentax-compatible T/S setups tilt far enough? Any WIDE setups? By setup I mean a T/S lens, or a lens on a T/S adapter. I know that severe tilts are possible with MF cams, but AFAIK not with smaller formats.
12-29-2010, 10:25 AM   #45
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QuoteOriginally posted by RioRico Quote
Indeed. But that requires a rather severe tilt, right? Do any Pentax-compatible T/S setups tilt far enough? Any WIDE setups? By setup I mean a T/S lens, or a lens on a T/S adapter. I know that severe tilts are possible with MF cams, but AFAIK not with smaller formats.

I believe I answered your question precisely two posts before this; the answer depends on how wide is wide and how tilted is tilted.

An entire 12" wide plane at a 60 degree angle (with respect to the plane normal) can be brought into focus with an 8 degree tilt lens (which is common for a tilt lens/adapter like the Hartblei).

When DOF is taken into account, a little more plane angle can be accommodated.
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