|
Forum: Winners' Showcase
08-16-2020, 11:58 AM
|
| |
I can't see how to vote! I would like to vote for this photo.
|
|
Forum: Pentax SLR Lens Discussion
04-19-2020, 01:24 AM
|
| |
Hello Rob
Thank you for this. It is this sort of factual information and the results of tests that I need. Perhaps I should have obtained this before buying the lens!!
As so-called “6x6 format” is not a 6cm × 6cm square, I hope that I may be able to get away with it – always assuming I can get the lens far enough back into the camera to obtain infinity focus!
Hasselblad specified the intended usable dimensions of the film image in “6x6 format” at 54mm × 54mm – even though the image recorded on the film is slightly bigger than this, generally 56mm × 56mm and sometimes a little larger, depending on the camera manufacturer and model.
For a square 54mm × 54mm, the diagonal is a little under 76.4mm, so it might be worth trying – if, as I say, making a suitable mount is possible.
If I am prepared to crop a little off two opposite sides, to create a rectangular image, I might be there. For instance, with a usable area of 54mm × 50mm, the diagonal is fractionally under 73.6mm. Considering the usable area to be 54mm × 48mm, the diagonal is 72.25mm, and for 54mm × 45mm, the diagonal is just under 70.3mm.
I could thus use a Pentacon Six camera to create images in either portrait or landscape orientation – and without needing to turn the camera through 90°.
The manufacturers of shift lenses often specify the limits to shifts, in order to obtain images with acceptable quality into the corners, and some shift lenses for “6x6” cameras specify that beyond a certain amount of shift, 10mm, for instance, a reduced area of the image (for instance, 6 × 45) should be used. See for instance here: Wiese Fototechnik shift & shift/tilt lenses
On the basis of these calculations, I am prepared to explore the possibilities further.
I will report back here, but given the current situation, several weeks may need to pass before I can take the next step!
Thank you again for your help!
Trevor
|
|
Forum: Troubleshooting and Beginner Help
04-18-2020, 02:19 AM
|
| |
Steve
Yes it is the Fotodiox TLT ROKR for Pentax 645 on Sony E. It seems to work well for shift. Not properly tested for tilt yet, but the locking screw needs to be really tightened up, or the lens begins to droop.
Your other comments noted. The conversion would be beyond the scope of my tools and skills, and at the present time there is no point in contacting people who might be able to do it, as they are presumably confined to their homes and unable to access lathes and other tools.
Let us hope that the world soon gets out of this crisis and that people will be safe.
Trevor
|
|
Forum: Pentax SLR Lens Discussion
04-18-2020, 01:47 AM
|
| |
Pepperberry farm
You are right. It is the larger format lens that I am interested in.
stevebrot
The frame diagonal is precisely the crucial factor. I will only find out by testing. If I could temporarily attach the lens to be Pentacon Six, at infinity focussing distance, I would be able to find out. Obviously, for closer focussing, the image circle will be larger.
Some people would dispute your comment that the Pentacon Six mount is a dead mount. Lenses are still being made with this mount, not only for the Pentacon Six and Exakta 66, but also because adapters from the Pentacon Six mount to a wide range of 645 format and 35mm format cameras, both digital and film-based) are so easy to make and so easy to find. For decades, the Pentacon Six was the most-used medium format camera in large sectors of the world.
If I make any progress, I'll report on it here.
Trevor
|
|
Forum: Pentax SLR Lens Discussion
04-17-2020, 05:08 AM
|
| |
Thank you, kypfer, for your suggestion. I will investigate the 35mm Fujinon 1.9 lens for 35mm “full-format” use.
Rob
Thank you for letting me come back to “haunt” you about a post you made five years ago, if I remember correctly. Thank you, also, for all the good, practical tips.
I was not familiar with SK Grimes, and will investigate.
Using this lens on the Sony A7Rii is an interesting bonus for me, but the real aim is to use it on “6×6” (2¼” square) film format, if it adequately covers the format, which is, strictly-speaking, 54mm × 54mm. If it does the job, it would be the widest rectilinear lens for this format and I would be keen to use it principally on a Pentacon Six, if making a suitable mount is possible.
|
|
Forum: Troubleshooting and Beginner Help
04-16-2020, 12:27 PM
|
| |
Having read the positive reviews of it on this forum, I bought a Pentax 645 35mm A lens. I have tested it on a Sony A7Rii full-frame camera, via a Fotodiox Tilt/Shift adapter. First results are very pleasing.
A reviewer on this forum said that it was easy to fix, and I would like to get inside it to see if it could be adapted for a Pentacon Six mount, for which I would need to get it about 3.5mm further back than now (for infinity focus).
I took off the black plate at the back (4 screws). I then removed the 6 screws that hold the shiny chrome plate that has the three lens mounting lugs or tabs, but couldn't get it off.
Any advice from any forum members would be appreciated.
My aim to explore feasibility; I don't have machining tools or skills, but if it appears that there is space to do what I am after, I would pass it on to someone with the appropriate skills and experience. It could then be easily also continue to be mounted onto Pentax 645 cameras via a Pentacon Six to Pentax 645 adapter, which is reportedly not hard to find (I have one on order, presumably held up in Customs). In this conversion I would expect to lose automatic aperture, but am prepared to accept that, as I use stop-down metering both on film cameras and on my digital camera.
Many thanks for any assistance!
Trevor
|
|
Forum: Pentax SLR Lens Discussion
04-16-2020, 12:12 PM
|
| |
Hello Rob
In your review of this lens you said it was easy to fix. I bought one based on the reviews on this forum and have tested it on a Sony A7Rii full-frame camera, via a Fotodiox Tilt/Shift adapter. First results are very pleasing.
However, I would like to get inside it to see if it could be adapted for a Pentacon Six mount, for which I would need to get it about 3.5mm further back than now (for infinity focus).
I took off the black plate at the back (4 screws). I then removed the 6 screws that hold the shiny chrome plate that has the three lens mounting lugs or tabs, but couldn't get it off.
Any advice from you or other forum members would be appreciated.
My aim to explore feasibility; I don't have machining tools or skills, but if it appears that there is space to do what I am after, I would pass it on to someone with the appropriate skills and experience. It could then be easily mounted onto Pentax 645 cameras via a Pentacon Six to Pentax 645 adapter, which is reportedly not hard to find (I have one on order, presumably held up in Customs). In this conversion I would expect to lose automatic aperture, but am prepared to accept that, as I use stop-down metering both on film cameras and on my digital camera.
Many thanks for any assistance!
Trevor
|
|
Forum: General Photography
04-02-2020, 11:31 PM
|
| |
Thank you to everyone for filling in the gaps in my knowledge.
Let's hope that - despite the lack of advance announcements - Ricoh will come up with a larger sensor and a higher resolution.
Trevor
|
|
Forum: General Photography
04-02-2020, 01:00 PM
|
| |
Hello
Does anyone know if there are any plans by Ricoh to release a Pentax 645 based on the sensor in the new Hasselblad H6D-100c? Its sensor has the dimensions 53.4 x 40.0mm, so it will apparently be the first medium format digital camera with a sensor that is very nearly the same size as the image frame in the 645 analogue cameras of the film area. Hasselblad state a resolution of 100 megapixels (11600 × 8700 pixels, 4.6 × 4.6 μm) with the CMOS sensor.
UK price is currently somewhat over GBP31,000. A challenger from Ricoh/Pentax at their price point would be most welcome!
Trevor
|
|
Forum: Troubleshooting and Beginner Help
03-31-2020, 11:48 PM
|
| |
Sandy
Thank you for this information and advice.
Trevor
|
|
Forum: Troubleshooting and Beginner Help
03-31-2020, 12:00 AM
|
| |
Thank you. Is there an older version of the 25mm f/4 lens for Pentax 645 that does have a physical aperture ring?
|
|
Forum: Troubleshooting and Beginner Help
03-30-2020, 06:33 AM
|
| |
Hello
I am planning to buy a Pentax 645Z and various lenses, including the 25mm f/4. I would also like to use the Pentax 645 lenses on a Sony A7Rii via the Fotodiox Pro TLT ROKR - Tilt / Shift Lens Mount Adapter for Pentax 645 (P645) Mount SLR Lenses to Sony Alpha E-Mount Mirrorless Camera Body.
I can't see an aperture ring on the lens, so is there any way that I can change the lens aperture when using this or other 645Z lenses on the A7Rii?
Thank you for your assistance!
Trevor
|
