Hassy 28mm sampels

[David Grover / Capture One]

Hi David,

when you use DAC, do you lose image "real estate"? As far as I know DxO delivers around 96 % of the original image and Canon DPP only 92 %. And if, does it depend from the lens?

Best,
Johannes

Yes you are correct in assuming it will depend on the lens.  Distortion is non existent in the longer lenses so real estate is 100%.

Obviously the HCD28 requires the most amount of correction.  I post two images from the HCD28 so you can layer them in PhotoShop and see the difference.

[attachment=8991:NoDAClo.jpg]
This image has no distortion correction.


[attachment=8992:DAClo.jpg]
This image has the distortion correction.

David

[Lust4Life]

David,

In studying Elizabeth Carmels work on her web site, and I understand she is a H3D user, I notice she is consistently getting DOF that you would normally get with a 4x5 and tilt = from foreground to infinity appear in sharp focus.

Do you know what technique she uses to accomplish this?
Helicon Focus was my guess but I'd like to know.

I've just purchased the H3DII-39 Kit with the optional 28mm D-Lens.  Moved from Phase P45+ on H2.

[David Grover / Capture One]

Hi Jack,

Congrats on your new purchase!

I haven't met Elizabeth so I am not sure.  I have a feeling she could be a member on the Hasselblad Digital Forum, so you could ask her yourself!

www.hasselbladdigitalforum.com

But my guess would also be Helicon Focus (now part of CS4 I believe.)

David

[Dustbak]

Is that so? Did Abobe take over Helicon and has it integrated Helicon focus into CS4? I knew there was focus blending in CS4 which I find very interesting.

[stewarthemley]

Having recently bought Helicon, and yesterday CS4, with my record on timing such matters, it wouldn't surprise me at all if Adobe have incorporated it!

[Mark_Tuttle]

We have that of course.    

David

(H3D39 at 0.35m)

Thank you very much.

Mark

[hubell]

Is that so? Did Abobe take over Helicon and has it integrated Helicon focus into CS4? I knew there was focus blending in CS4 which I find very interesting.

I have Helicon Focus, but I just purchased an upgrade to CS4 in the hope that Adobe has done its own focus blending code and it is better than Helicon. When I made the switch from shooting 6x7 film to an H3D-39 two years ago, I was quite frustrated by how difficult it was achieve acceptable depth of field with the H3D-39 compared to my Pentax 67. In part, this was due to the fact that I was advised not to stop down below f/16 with the H3D. What I think was more significant is that the resolution of the H3D-39 with the HC lenses is so amazing that the elements that are in perfect focus in a frame make the elements that are not look more out of focus than I found in my 6x7 film. In short, the depth of field is just less as a practical matter. As a result, I have taken to bracketing for focus on a regular basis and a good software solution for blending is very important to me. Helicon is quite good, but not always perfect. It will be nice to be able to do it within PS with all of the PS tools at your disposal.
BTW, Elisabeth Carmel has a blog and you can ask here there whether she uses Helicon.

[FlashDB]

Yes you are correct in assuming it will depend on the lens.  Distortion is non existent in the longer lenses so real estate is 100%.
Obviously the HCD28 requires the most amount of correction.  I post two images from the HCD28 so you can layer them in PhotoShop and see the difference.
[attachment=8991:NoDAClo.jpg]
This image has no distortion correction.
[attachment=8992:DAClo.jpg]
This image has the distortion correction.
David

Hi

I managed to find a C1 4.5 and Mamiya 35mm lens correction test, posted by Guy Mancuso on forum.getdpi.com:
http://forum.getdpi.com/forum/showthread.p...3692&page=2  (Go to post #40 to see the images)

Is it me or doesn't the corners look like 4.5 is adding USM as an attempt to improve resolution?

/David

[lisa_r]

Hi Michele, I am wondering if someone walked through the room during the exposure. In that first shot I see some blurry milky looking band right through the image from approx. that easel going right. Looks like flare or some kind of blur or ghosting. Any idea?

[michele]

Hi Michele, I am wondering if someone walked through the room during the exposure. In that first shot I see some blurry milky looking band right through the image from approx. that easel going right. Looks like flare or some kind of blur or ghosting. Any idea?

Hi Lisa,
yes you are right, It was my dealer that was walking into the room...  I didn't mention it because it doesn't effect the corners of the image, and I'm concerned about that not the center... Afeter many attempts, I got a very good TIFF from the RAW, and I'm sure that the HCD 28mm it's a very impressive lens

[David Grover / Capture One]

Yes there are more than 50 000 lookup tables in Phocus.
Here's a quick DAC primer.

No lens is perfect. Every lens suffers from some degree of distortion, chromatic aberration, or vignetting. By shooting test charts at various apertures, focal lengths (think zoom), and combinations of extension tubes, you can mathematically describe these characteristics.

The CRUCIAL bit of data however is the subject to sensor plane distance, without this data you CANNOT make accurate corrections only guesstimates. This is why some software asks you to specify wether the shot was taken at near or infinity focus. As far as I'm aware the H system is the only system that passes subject to sensor distance back to the software.

The system is able to work with the HTS because the HTS has sensors that record the degree of tilt/shift/rotation and pass it back (you can see it in meta data), again this is the only tilft/shift system I know of that does this.

Nick-T

Small correction!

DAC data tables are not constructed via shooting test charts.  We use mathematical data from the optical design software to calculate the corrections.  This is better and more accurate practice than shooting test charts.  Which is how lens corrections in 'other' software would have to work as they do not have access to the optical design.

We are now close to 57,000 data tables with the latest being Ultra Focus data for the new 35-90 zoom lens and of course the HTS.  VERY many tables!    

Best,


David