Hasselblad XCD lens and upcoming XD2 100MB?

Started 6 months ago | Discussions thread
Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 1,325
Re: Hasselblad XCD lens and upcoming XD2 100MB?

Rick Knepper wrote:

Mixart wrote:

Just curious - Can the current XCD lens range handle 100MB pixel, when the new Hasselblad XD2 100MB comes later?

https://cdn.hasselblad.com/04e9d0f7-abdf-434d-8b5b-364c69af21ec_x-h-system-lenses_v2_28feb2017_a.pdf

Interestingly, in this Hasselblad lens booklet, it says all HC/HCD lenses are fully 100MP+ compatible. I couldn't find the same statement in the XCD section. Doesn't necessarily mean it is not there or isn't so.

All Fuji GF lenses have a similar 100 MP statement on each lens page on the Fuji website.

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Once you've done fifty, everything else is iffy.

Hi,

The MTF data given by Hassellblad for the X-lenses are extremely good. Significantly better than with the H-lenses.

Hasselblad measures their MTF data, so they are not calculated MTF or made up by the marketing department.

Essentially making the sensor smaller "automagically" improves the lenses. So just downscaling a lens will improve it's performance. But a smaller format needs more magnification. A simple explanation may be lens designs minimize angular errors. So if you go for a smaller format you will need a shorter focal length for the same field of view (FoV) and the shorter focal length will project that angular error over a shorter distance.

The X-system does not need to have room for a moving mirror and that gives more freedom for lens designers. Especially, more symmetric designs may be used. Symmetry is good, as having a symmetric design can cancel out many aberrations caused by the lens elements. So, assymetric designs are more complex.

If you check the MTF data, you can see that MTF does not improve a lot when stopping down. That is a very strong indication that the lens is well corrected to begin with.

Personally, I have the following idea of a very good lens:

  • MTF 10 lp/mm > 90
  • MTF 20 lp/mm >80
  • MTF 40 lp/mm >60
  • All figures above for both sagittal and tangential structures across the field.

The brochure Rick referred to has the MTF data:

https://cdn.hasselblad.com/04e9d0f7-abdf-434d-8b5b-364c69af21ec_x-h-system-lenses_v2_28feb2017_a.pdf

Increasing resolution of the sensor is always beneficial. The pixel aperture has a softening effect. So the pixel has an MTF on it's own.

Brandon Dube an optical designer working for OLAF Optical Testing but also for NASA has a very nice article on the issue here: https://www.lensrentals.com/blog/2017/10/the-8k-conundrum-when-bad-lenses-mount-good-sensors/

But just look at this figure from the article above:

This shows the MTF of perfect lens combined with the OLP filter and an 5 micron pixel aperture. Very clearly, pixel aperture dominates MTF.

A very good lens will perform best close to full aperture, as stopping down increases diffraction. Contrary to common belief, diffraction is a property of light, nothing optical designers can do about it.

But, if you have a smaller sensor, you would need to stop down less för the same depth of field (DoF). So, if you would use f/8 on 54x40 mm you could use f/6.2 on 44x33 on 44x33 mm.

Just to mention, Fuji has a neat trick for improving sharpness. They have microlenses that don't cover the whole pixel. So, they reduce the pixel aperture and that will increase system MTF leading to sharper images at a price of lower sensivity and more aliasing.

Best regards

Erik

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Erik Kaffehr
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