Author Topic: hdz file format  (Read 44502 times)

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guest84672

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Re: hdz file format
« Reply #15 on: January 30, 2011, 01:58:01 pm »
You can control the gamma and brightness of the HDRI, as well as the gamma and brightness of the entire image. That gives a lot of control.

Offline MealeaYing

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Re: hdz file format
« Reply #16 on: June 17, 2016, 11:26:56 am »
Ok!
I learned a lot here, I  think...

Let me make sure I understand this:

1) HDR is just high dynamic range, this can be saved in any format, but usually Jpeg (8 bits per R, G, and B channels) by cameras, phones and so on.

2)HDRI has an extra I for whatever reason, contains 32 bits of information, giving not only color information, but also lighting. Most cameras and phones don't do this, right?

3) Doing a panoramic image with your camera or phone, even with HDR on, will result in a normal HDR image (albeit rather cool) thats NOT useful in KeyShot as it hasn't got lighting information, and does not map well onto (Into?) a sphere.

So, this brings me to a simple question:
Can a phone or camera that supports HDR, supports doing panoramic photos, and has good resolution actually make a proper (KeyShot worthy) HDRI image?
I have, for example, a Droid Turbo 2 with a nice 21 megapixel camera in it, it does HDR, it does panoramas and it does stills and 4k ultra HD, can I use this thing somehow to make these images or am I hosed?
If I am hosed, what camera do I need?
And, I hate asking this, but, how much is it?

Thanks for this thread you guys, I think I understand this better...

Cheers!
Mealea







guest84672

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Re: hdz file format
« Reply #17 on: June 17, 2016, 02:38:56 pm »
You can use those panoramic photos. In order to turn this into an HDRI, you will need to open the HDRI editor (KeyShot Pro) and add pins to it. Otherwise the lighting will be just flat.

In order to create true HDRIs you will need a camera that allows you shoot images at different exposure that need to be clamped into a single image. There are various tool out there that allow you to do this. Creating spherical HDRIs is another step up where you will need additional hard- and software.

Offline Niko Planke

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Re: hdz file format
« Reply #18 on: June 24, 2016, 06:29:56 am »
To clarify a few things.

HDR stands for High Dynamic Range and is the basically same as an HDRI (High dynamic range Image).
These are ideally save with as much accuracy as possible, so any 32 bit image format. (Tiff, exr,hdz, hdr or  "a specialized HDR-JPEG")
By  saving the files as a standard jpeg you will usually cut the high range.
This results in bright light sources being darker  than they should be.
This can not be reversed, so  you can not make a normal image to an hdri.

To capture the additional information, multiple images with different exposures are taken.
This can be done by any camera that with a accurate enough exposure control.
You should be able to find mobile apps that can take HDR images.
But it is worth noting that any movement in between the shots will spoil the outcome.

The challenge is usually not the hdr image itself, but the spherical representation with hdr information.
So to use panoramas  from mobile devices you would need to overlay multiple panorama images with different exposure,  and make sure that the complete sphere is captured and not only a horizontal band(like panoramas usually are). And all of that while nothing has moved between the shots.

As for the hdr setting, it simply takes the the images with different exposures for you , so they should be valid hdris if saved in the right format.
If you manage stitch multiple of those hdris into on spherical hdri, it should be god to go inside KeyShot.

So taking HDRIs with you mobile device is a quite ambitious task and it may be cheaper after all to buy the needed gear.

Usually HDRIs are made using  a fisheye lense and a specialized camera stand.   You should be able to find multiple Guides to do so online.

But the main Method is to take images in each direction, each with multiple exposures.  an those can then be stitched into a spherical HDRI.
That can be done with most cameras, but the image quality  and the time required will of cause depend on the gear used.
You should also be able to find sets that are able to directly take  360 degree HDR images with one button press by searching for "360 hdri camera" in your favorite search engine.

If you only have a jpg panorama, it can not directly be used since you may be missing part of the image(top and bottom) and the High dynamic range information.
You can compensate for the missing HDR  information by adding Pins in the Bright areas as described  above.
For instance, adding a bright circular Pin where the sun is. But you will have either a stretched images  or dark areas at the top and bottom of the image.