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Author Topic: Counting Ants  (Read 19256 times)
mtomalty
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« Reply #20 on: March 29, 2006, 10:29:14 AM »
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Here is an LCC exposure for this lens
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mtomalty
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« Reply #21 on: March 29, 2006, 10:31:34 AM »
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Just to clarify,the test images above were captured using a P25 and not the P45
and,FWIW,I am not an owner of either back,yet

Mark
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ddolde
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« Reply #22 on: March 29, 2006, 10:38:09 AM »
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This alone (not to mention the cost) would ruin a P back for me. Never saw this on my Kodak Pro Back.

4x5 film doesn't have these issues.
« Last Edit: March 29, 2006, 10:38:39 AM by ddolde » Logged
mtomalty
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« Reply #23 on: March 29, 2006, 10:58:17 AM »
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Here's a before/after example of LCC being applied to a P25 file

The Before
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mtomalty
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« Reply #24 on: March 29, 2006, 11:00:22 AM »
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And After

Apart from shooting the exposure in the field the application of the LCC correction from
within Capture One takes only a couple of seconds per image
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mtomalty
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« Reply #25 on: March 29, 2006, 11:12:09 AM »
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Doug,

The color cast also gives me a knot in the stomach but,in practice,the correction routine
takes a mere seconds.

What also makes me cautious is that the corrections can only be applied from within CaptureOne
and as a result one is then tied to that software to process images the could be seen
as color cast challenged.

Workflow aside,I find i like the results I've been getting processing P25 files through ACR
better than what I get in CapOne and i'm certain i'm in the VAST minority with that view.
I still find that CapOne files apply a little too much smoothing for my taste for some images
that results in a subtle 'watercolor' effect in some areas of fine detail-like distant trees and
foliage,etc. ACR results might be ever so slightly 'grainier' is sky areas but the clarity of
fine details at a distance are more in line with what I expect from a 'large format' capture.

Mark
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alainbriot
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« Reply #26 on: March 29, 2006, 12:04:03 PM »
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Only shifts, unless the tilts are significant.

Michael
-----

In my work with 4x5 I just about use tilts only, and most of the time movements are relatively minor. The only instance I use shifts is when I want to keep a vertical... vertical, which is rare.  Totem Pole in Mt Valley is one of the very few instances I recall where shifts were necessary.  Very tall and very close, if you shoot from within the Sand Dunes at the base of the Totem Pole.  I don't even use tilts with Spiderock since it is quite a ways from the rim of Canyon de Chelly and down below the horizon.  

In many instances with landscapes minor distortions due to tilting the camera upwards are unnoticeable because there are no straight vertical lines.  However, trees are one notable exception.  So, when I want to shoot trees and keep them perfectly vertical, I use a telephoto because it allows me to stand further back and shoot level.

All this to say that the color cast would'nt be a problem for me if I used the P45 (which I may...).  Seems like all this is a lot of ado about nothing, unless you use shifts regularly (when photographing architecture for example).

Alain
« Last Edit: March 29, 2006, 12:18:33 PM by alainbriot » Logged

Alain Briot
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collum
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« Reply #27 on: March 29, 2006, 12:31:48 PM »
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Only shifts, unless the tilts are significant.

Michael
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All this to say that the color cast would'nt be a problem for me if I used the P45 (which I may...).  Seems like all this is a lot of ado about nothing, unless you use shifts regularly (when photographing architecture for example).

Alain
[a href=\"index.php?act=findpost&pid=61280\"][{POST_SNAPBACK}][/a]

yes.. for normal landscapes, i pretty much just use tilts as well... but i also do urban and industrial landscapes, and this is the area i'm concerned with.

     jim
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Jack Flesher
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« Reply #28 on: March 29, 2006, 12:32:42 PM »
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Mark:

Thanks for posting these examples and the link!  

A couple of questions:

1) Approximately how much rise or shift was being used in the posted images? It appears as though it may have been very little in both images, unless it was an extreme shift and not rise/fall.

2)  Have you noticed this effect with tilts?  In the Phase link you provided they indicated it is also a problem with tilts in some lenses.

3) Lastly, how effective is the software at completely removing the shift, and does it destruct the image or image detail in any other way? (I ask because on my monitor it appears the "corrected" image still has some residual color issues in the affected central area.  Is this just a function of the web jpeg-ing or can you see it in the original file?)

Thanks!
« Last Edit: March 29, 2006, 12:38:06 PM by Jack Flesher » Logged

mtomalty
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« Reply #29 on: March 29, 2006, 12:42:30 PM »
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Alain

The two images I posted were unshifted,untilted captures and clearly show the cast.

I have only very limited experience with the P45 but I would assume it behaves in
a very similar way with wide angle lenses as does the P25

I have also gotten colorcast on P25 files using Hasselblad V series lenses 50 (obvious)
and 80mm (subtle) and the SWC-M with 38 biogon (severe) so camera movement is not
the only criteria one needs to be aware of.

Leaf Aptus22 files using the identical lenses shows no colorcast whatsoever.
Unfortunately, Leaf has traditionally had noise issues with long exposure times where
Phase excels.  
Eight to ten seconds seems to be the cutoff point for Leaf files in my tests but newer back
files (A75) seem to be significantly improved.

Mark
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Boghb
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« Reply #30 on: March 29, 2006, 12:44:13 PM »
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Alain

The notion that color cast is present only with extreme wides and/or movements is simply incorrect.  It is present in all of my images, regardless of the lighting situation or which lens I use.  My second worst lens in this regard (after the 24mm digitar) is the 250 SA CFE.  I have now changed 3 backs and the problem persists.

In light of this, would you still say this is much ado about nothing?
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Jack Flesher
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« Reply #31 on: March 29, 2006, 12:46:24 PM »
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The two images I posted were unshifted,untilted captures and clearly show the cast.

[a href=\"index.php?act=findpost&pid=61289\"][{POST_SNAPBACK}][/a]

OUCH!!!  That does not sound good at all...  Perhaps the new Aptus 75 is worth consideration...
~~~

On the subject of rise/shift in landscape images: I often use rise/fall in landscapes instead of tilting the entire camera, but then it's easy to impart rise and shifts on my camera...  Each to their own method...  

FWIW, I do agree that the perspective distortions are not detectable with most landscape images due to no regular parallel lines (forests full of trees excepted), but the resulting image taken both ways will often look different.  Not that one is worse than the other, just that the difference can be seen
« Last Edit: March 29, 2006, 01:00:16 PM by Jack Flesher » Logged

Jack Flesher
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« Reply #32 on: March 29, 2006, 12:51:12 PM »
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It is present in all of my images, regardless of the lighting situation or which lens I use. [a href=\"index.php?act=findpost&pid=61290\"][{POST_SNAPBACK}][/a]

Boghb:  Was yours with a P25 or P45?  

Michael:  Did you see any color shift in un-shifted images with your P45?
« Last Edit: March 29, 2006, 12:51:53 PM by Jack Flesher » Logged

mtomalty
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« Reply #33 on: March 29, 2006, 12:52:34 PM »
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Jack,

In my experience (and again i want to state that I am not a phase back owner and am
basing my observations  on only a few hundred  files) Capture One has eliminated the
color cast to my COMPLETE satisfaction and any residual color shift that might be seen
on the reference images i posted is not present in the original 16bit file.

Mark
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ddolde
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« Reply #34 on: March 29, 2006, 12:55:13 PM »
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Wouldn't the Aptus 75 have the same problem?   I am slso curious why the 1Ds2 doesn't have this same problem.

Leaf has some nice sample raw files.  Mostly of pretty feathered birds though if you know what I mean.  Apart from the subject matter I found them to be pretty amazing and requiring very little post processing.

http://www.leafamerica.com/products/products_aptus75.asp
« Last Edit: March 29, 2006, 12:56:20 PM by ddolde » Logged
Jack Flesher
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« Reply #35 on: March 29, 2006, 01:01:54 PM »
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Jack,

Capture One has eliminated the
color cast to my COMPLETE satisfaction
[a href=\"index.php?act=findpost&pid=61294\"][{POST_SNAPBACK}][/a]

Thanks for the clarification Mark!
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alainbriot
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« Reply #36 on: March 29, 2006, 02:16:58 PM »
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Wouldn't the Aptus 75 have the same problem?  I am slso curious why the 1Ds2 doesn't have this same problem.

Leaf has some nice sample raw files. Mostly of pretty feathered birds though if you know what I mean. Apart from the subject matter I found them to be pretty amazing and requiring very little post processing.

http://www.leafamerica.com/products/products_aptus75.asp
[a href=\"index.php?act=findpost&pid=61295\"][{POST_SNAPBACK}][/a]

I have seen and worked with Aptus 22mp  files created with a Hasselblad H2 and they are free of any color shifts whatsoever.  No more post-processing needed than with a 1DsMk2 file. Very sharp images too.

Alain
« Last Edit: March 29, 2006, 02:17:11 PM by alainbriot » Logged

Alain Briot
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Boghb
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« Reply #37 on: March 29, 2006, 04:43:23 PM »
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Jack, I have the p45.  I had the p25 before that, but I never noticed lens cast with it.
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Jack Flesher
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« Reply #38 on: March 29, 2006, 06:36:38 PM »
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Jack, I have the p45.  I had the p25 before that, but I never noticed lens cast with it.
[a href=\"index.php?act=findpost&pid=61312\"][{POST_SNAPBACK}][/a]

Thanks for that clarification Boghb, but I really did not want to hear this...      

FWIW I recently saw some files from a friend's P45/Hassy H lenses and have to say I was extremely impressed!  But for my uses I really need to be able to use whatever back I get on a view camera with movements and I don't like the idea of doing the white frame for every image, shifted, tilted or not...  It sounds like I'll need to take a harder look at the Aptus 75.
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BernardLanguillier
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« Reply #39 on: March 29, 2006, 07:36:48 PM »
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The Hassy 39 backs might also be worth checking out, although the Phase problem appears to be a Kodak problem...

I have been considering a DB for some time as well, but there is no way I would be getting into individual image calibration... certainly not after spending this kind of money!

I am looking forward to MR's analysis of this.

Regards,
Bernard
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A few images online here!
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