Can the Lens-ROMs be modified?

tempelorg · 05-13-2015, 03:53 AM

Those who have followed the various Hacking threads (e.g. https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/250555-resurrect...e-hacking.html) or learned about the "Developer Mode" menus already know that there are so-called Lens ROMs.

They contain parameters for Phase-detection Auto Focus.

Now, having several Zoom lenses whose focus is not evenly sharp across the entire focal range, I wonder if I could try modifying them myself.

In particular, I like to try this with a Tamron lens (17-50mm f/2.8 DiII), which is cheap enough to give up if I should break it. Another candidate is a Sigma 150-500 OS.

I believe something can be done with USB adapters, but I cannot find any specifics on this.

Any pointers?

Timd · 05-13-2015, 04:06 AM

Do a search on Lensrom and Lenseep or on "how to deactivate SDM" and you will find the procedure to copy from the lens to the SD card. However, I am not sure the lenseep.lns files have been decoded.

I would suggest that you copy and save the lenseep.lns file and keep in a safe place so that you can always copy it back to the lens if all fails. However, I'm not sure if you can brick a lens in the process.

Have fun: let us know what you find!

tempelorg · 05-13-2015, 04:19 AM

Timd, I know that I can read Lens ROM. What I don't know is how to write them back. Are you saying that the threads you suggest do answer that question?

---------- Post added 13th May 2015 at 13:29 ----------

Nevermind - I am kind of dim. I totally forgot that you can also write the data back from the camera to the lens in developer mode.

vonBaloney · 05-13-2015, 06:53 AM

You'll want to look at this:

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/251464-coll...-lensroms.html

tempelorg · 05-13-2015, 07:43 AM

BTW, is it known to the users of this forum that someone in a German forum actually managed to decypher most of the meaning in the lenseep file, i.e. which positions relate to which focal length ranges and such?

It appears that at least one person (Volker, voko) managed to fix a focus jump himself by messing with the values.

See DSLR-Forum - Einzelnen Beitrag anzeigen - Da*50-135 AF Brennweiten- UND Blendenabh

05-13-2015, 03:53 AM	#1
tempelorg Senior Member Join Date: Apr 2011 Location: Munich Photos: Gallery Posts: 203	Can the Lens-ROMs be modified? Those who have followed the various Hacking threads (e.g. https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/250555-resurrect...e-hacking.html) or learned about the "Developer Mode" menus already know that there are so-called Lens ROMs. They contain parameters for Phase-detection Auto Focus. Now, having several Zoom lenses whose focus is not evenly sharp across the entire focal range, I wonder if I could try modifying them myself. In particular, I like to try this with a Tamron lens (17-50mm f/2.8 DiII), which is cheap enough to give up if I should break it. Another candidate is a Sigma 150-500 OS. I believe something can be done with USB adapters, but I cannot find any specifics on this. Any pointers?

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05-13-2015, 04:06 AM	#2
Timd Senior Member Join Date: Dec 2008 Location: Cape Town, SA Posts: 262	Do a search on Lensrom and Lenseep or on "how to deactivate SDM" and you will find the procedure to copy from the lens to the SD card. However, I am not sure the lenseep.lns files have been decoded. I would suggest that you copy and save the lenseep.lns file and keep in a safe place so that you can always copy it back to the lens if all fails. However, I'm not sure if you can brick a lens in the process. Have fun: let us know what you find!

05-13-2015, 04:19 AM	#3
tempelorg Senior Member Join Date: Apr 2011 Location: Munich Photos: Gallery Posts: 203 Original Poster	Timd, I know that I can read Lens ROM. What I don't know is how to write them back. Are you saying that the threads you suggest do answer that question? ---------- Post added 13th May 2015 at 13:29 ---------- Nevermind - I am kind of dim. I totally forgot that you can also write the data back from the camera to the lens in developer mode.

05-13-2015, 06:53 AM	#4
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	You'll want to look at this: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/251464-coll...-lensroms.html

05-13-2015, 07:43 AM	#5
tempelorg Senior Member Join Date: Apr 2011 Location: Munich Photos: Gallery Posts: 203 Original Poster	BTW, is it known to the users of this forum that someone in a German forum actually managed to decypher most of the meaning in the lenseep file, i.e. which positions relate to which focal length ranges and such? It appears that at least one person (Volker, voko) managed to fix a focus jump himself by messing with the values. See DSLR-Forum - Einzelnen Beitrag anzeigen - Da*50-135 AF Brennweiten- UND Blendenabh