Posts: 3
Registered: ‎04-28-2016

Pentax Firmware features manual lens support we need this! F--

I have been a Pentax user for many years my first Pentax was a k1000 and my latest is the K5, I was also considering the k30 and k50 (but the K5 won) I must have around 25 lenses which are compatible with the K5 some are DA KA KM and M42 mount.  I have Pentax lenses, Takumar lenses, as well as russian, german lenses and other third party lenses from several manufacturers. It is fantastic that Pentax has support for all these lenses right through to the Pentax K1 and all benefit from the inbody camera SR in all the Pentax DSLR's.


The Germination of an Idea


One of the features of the k5 is that you can enter photographer and copyright into the camera and it is written into the Exif everytime you take a shot. That is useful but it doesn't have to be used that way.  Currently my photographer name is john tokina 24mm f8 sometimes it can be tokina 24mm f2.8 or Even Pentax Km 75-150 90,f4. :)


Why do that? 

well generally i will use a lens for the day or maybe the hour, i tend to be using the same F-stop for the same kind of shot.

Thats the biggest problem really F-Stop it takes discipline to take the time to record it. The lens details is not such a problem as i don't change lens every other shot. 


When it comes to post processing later I need to recall which lens I was using and the settings. This allows me to evaluate my lenses see what worked well and what didn't and helps to improve my over all photography. 


Talking with another photographer he said "I just checked on my D700. I have a completely manual 35mm f/2 lens attached. In the settings menu, under Non CPU lens, I have that lens entered. The photo taken with it shows the focal length (with an asterisk) and the f-stop used. "


Nikon let him have that custom field and so he can have correct Exif information. When he comes to process the raw image he has an advantage over me.


I think Ricoh-Pentax can do better than that, much better and make users very very happy.


The Km Ka difference,

With a KA lens the camera can set the aperture and meter correctly.  It can get the focal length from the value entered into the SR so the Exif will say e.g 50mm f4 1/250 iso 200 for example with a km it might be 50mm f-- 1/250 iso 200

Thats not bad but it could be better, much better.


The KA lens has an aperture lever movement proportional to the aperture the lens code the series of insulated and non insulated spots give a maximum and minimum aperture for that lens and so the camera can set an aperture on the lens. With the Km mount this information wasn't there the aperture lever movement wasnt proportional which is why the use of a pin that extends when the ka lens has its aperture ring set in the A position.


Hacking the lens mount.


With a little foil its possible to fool the camera into thinking it has a KA mount lens with 11 x 111 as the code since it is a metal mount. This basic hack enables an f-stop to be recorded, it's upto the user to ensure that corresponds with reality.


I had a km mount adaptall already on an 80-200mm tamron I decided to have a play and see what happens when you tell the camera its got the ka mount and apply the appropriate lens code. With these lenses the mount can be changed between a km and a ka version. For the code i just used some tape to insulate a couple of pins to give the correct maximum aperture. It worked!


The body thought the km lens was a ka and gav me f-stop as it would with a real KA.  However with the lever not moving in proportion to the lens, there was exposure error varied with aperture. At some apertures it was spot on but mostly there was a difference between 0.3 of a stop plus or minus (which was recoverable in raw) some apertures were spot on.  Anyway knowing the offset for a particular aperture I can manually correct for this metering error or should I say aperture error.


So with the photographer hack and the tinfoil hack, yes I can work around the limitations of the Pentax firmware but it is just firmware and it doesn't need to be that way.  


Here are my proposals to improve the camera firmware on existing or future Ricoh Pentax models, admittedly for non current models I can't imagine that Ricoh Pentax would be inclined to expend the resources to make the modified firmware and the amount of free space left may make it impossible to add the modifications (although couldnt some of this be stored on the SDcard, a bit of a kludge).  


Identifying a Classic Lens


Starting with the fact that a non ka lens doesnt have the electrical contact with the body it is easy to distinguish a modern lens from a classic lens.


So first of all user lens profiles.

This would be


lens make


serial number  *these first 3 fields could be one.

Maximum Aperture

Minimum Aperture


for each f-stop a metering correction would be stored the value to be determined by the user. This would be possibly a maximum of 8 values for my tokina lens there are 5 clicks. 

Metering compensation on/off Flag

Focal length Max and Minimum

Teleconverter value 1, 1.4, 1.7, 2, 3...  *use of a teleconverter changes the SR needed. 

Extension tube in mm 0-99 mm would cover it


The more lens profiles stored the better. One would be a help, more would be better , who wants to be out and about entering this information when you can just access a profile from a menu drop down. The data stored for a individual lens would be tiny. 


Change to operation of the camera

With a lens registering as f--

The front and rear wheels can be used to dial in f-stop and focal length

with some km lenses a real compensation can be applied for the profile in use, If there was profiles for modern lenses any Exposure adjustment quirks for a modern lens could be applied automatically on a per lens basis.  Just as for rear and front focusing lenses can be compensated for already.


with some lenses the f-stop recorded would really just be a note as to what the user set the f-stop too. which would be useful when processing an image and review. 


Focal length on modern lenses the lens supplies. The focal length with older lenses the user needs to enter it manually. By assigning the front wheel to setting this value the user can see that he has the zoom set at 75mm and enter it if it is 150mm for the next shot he can spin the wheel and enter the new value rather than diving into the menu's to do so.


Focus distance might also be able to be entered.  With the k5 you can assign some buttons , so focal length or focus distance could be adjusted with the wheel depending on user preference. e.g for a prime focus distance would be something that would change between shots and focal length wouldn't need adjusting between shots for the SR to work to best effect.  For Zoom lenses the priority would be focal length being used. 


Post Processing of Images

Since the Exif information is more complete, it becomes possible to apply a Lens profile for a specific lens, knowing the focal length that was used with a telephoto the correction at the short end would be different to the long end. Also things like CA can also be applied to suit the lens profile. Profiles may also want to be camera/lens specific  with different profiles being applied for say k1/ lens and k3 /lens.


Community driven development for different  software packages. 


Pentax photographers will be able to cooperate with generating in camera profiles and post processing profiles. For literally 1000's of lenses.


Why would Ricoh Pentax want to add these features to their camera firmware?

Well for existing Pentax camera owners it gives good reason to upgrade and to a newer camera model knowing they can do more with their existing lenses. I accept that it would not be economically viable to update firmware on older models but for current and future models it would be awesome and just from a firmware change.


Would it effect lens sales for current lenses negatively, no since modern lenses have Auto Focus and Weather Sealing that can't be added to a vintage lens. There are different reasons for buying particular lenses.


Would it increase sales of new pentax camera models almost certainly  this additional firmware feature with better support for older lenses would be one more reason to upgrade to a new model. Ask your Engineers how much work it would be to add this support into the existing firmware model and I think you would find it is quite a small engineering cost for something which can be flashed into existing hardware.


I hope you can pass this on to the right people


warm regards