Please Advise - Short List for Wide Lenses for IQ3 100 Achromatic

[Doppler9000]

Hello,

I am wondering what wide, ~ 35mm, lenses people recommend that will work well with the IQ3 100 Achromatic back.

Thank you in advance.

 

[Paul Spinnler]

With an achromatic back you don't need to worry about magenta cast. Following lenses will work well:

SK 35 XL -> you need CF though
RS 35 HR-S -> No movement, but an absolutely excellent lens for landscapes etc.
RS 32 HR-W

With a 100MPX chro back and wide angles would definitely recommend late-gen lenses given the resolution. For teles it would not be such a strict recommendation to go for HR and Apo Digitars.

The 32 HR-W is very high quality and one of RS' bestsellers – @vonalpen sells one in AS for a killer price.

The RS 35 HR-S was the lens bundled with the Alpa A-Series systems which were based on colour and achromatic 100 MPX backs.

BR
Paul

 

[rdeloe]

With an achromatic back you don't need to worry about magenta cast. Following lenses will work well:

Can you explain the technical argument behind this point Paul?

Obviously there's no magenta colour cast, but colour cast is due to sensor crosstalk. Are you saying there is no crosstalk on an achromatic back? If there is crosstalk, then luminance values will be wrong due to sensor crosstalk in affected areas.

 

[Paul Spinnler]

Can you explain the technical argument behind this point Paul?

Obviously there's no magenta colour cast, but colour cast is due to sensor crosstalk. Are you saying there is no crosstalk on an achromatic back? If there is crosstalk, then luminance values will be wrong due to sensor crosstalk in affected areas.

Well I don't see any problems that look like luminance changes from potential color cast on my IQ4A, but to be honest, I have never deep dived on this and maybe there are subtle traces of an effect - I could one day compare the same shot with IQ4A and IQ4 and see if I see the cast in the IQ4 in the IQ4A.

I always thought all I see is vignetting but haven't done side-by-sides, which would be interesting.

 

[rdeloe]

Perhaps it works the same way as with purple fringing. I can see where the purple fringing was in the monochrome version (Right), but it's not objectionable anymore.

 

[P. Chong]

IQ4 is a BSI sensor, and it does not suffer from the same colour cast issues as the IQ3.

Well I don't see any problems that look like luminance changes from potential color cast on my IQ4A, but to be honest, I have never deep dived on this and maybe there are subtle traces of an effect - I could one day compare the same shot with IQ4A and IQ4 and see if I see the cast in the IQ4 in the IQ4A.

I always thought all I see is vignetting but haven't done side-by-sides, which would be interesting.

 

[Paul Spinnler]

IQ4 is a BSI sensor, and it does not suffer from the same colour cast issues as the IQ3.

That's clear - but it has color cast issues with wide angles still. Especially SK and you can see subtle cast with the Rodie wides too, although some mistake it as some nice tone in the sky.

I have both backs and have been on the IQ4 since 2019 ... and on IQ4A since 2023. I have not seen color cast induced issues, but have not done a detailed analysis of files of the same scene shot side-by-side. My thinking was to shift the 35 XL without CF and see if I can see any traces of difference between two backs.

As said, I have not so far seen something directly.

I've owned digital backs starting from P30, H39, Leaf Aptus 12 with 80 MPX and know a thing or two about this stuff ...

On top, I am not convinced that there are color cast induced cross talk luminance effects on achromatic shots. A few 35XL shots shifted without CF should provide an answer.

 

[anyone]

Often when I saw color cast, it came together with smearing. It would be interesting to know whether or not that issue persists with an achromatic back.