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Forum: Pentax Medium Format
01-09-2022, 06:41 PM
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You are using DSLR concepts to imagine what's going on on mirrorless, and that's why you are puzzled. Light rays do not reach GFX sensors with large angles if you use GFX lenses. If you actually look at the rear elements of native GFX wide-angle lenses, you will see that the diameters of the rear elements are much larger than Pentax native ones.
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Forum: Pentax Medium Format
11-29-2021, 04:26 AM
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Unfortunately I don't have the 90mm. I thought about getting one, but canceled that idea after I saw the performance of the 25, 35, and 55. To me, the 55 has to be stopped down to about F4.8 to be minimally acceptable for astro (particularly, for corner performance).
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Forum: Pentax Medium Format
11-28-2021, 05:42 PM
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Use both Pentax 645z and GFX-50R for astro. Can't comment on aerial photography. But if you need corner sharpness at large aperture, go to Fuji. The few Pentax lenses that I had used are all very sharp in the center, but quite lousy in the corners. They are miles behind Fuji lenses. They have to be stopped down by at least two more stops to get close to (not matching) a Fuji counterpart in corner sharpness.
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Forum: Pentax Medium Format
10-23-2021, 01:56 AM
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Same here for my GFX50R. It requires way much less cleaning than my 645z. Why? I believe it’s not sensor cleaning mechanism, as GFX50R doesn’t have IBIS. It’s the cover glass.
First, one needs to realize that you will never be able to clean the sensor, unless you completely take apart the camera and the sensor compartment. What you actually clean is the cover glass in front of the sensor. This is true for almost all cameras. (I use the word “almost” just to be conservative.)
On GFX cameras, the cover glass is placed well apart from the sensor. What this means is that even if there are many dusts on the cover glass, their shadows on the sensor will be way out of focus. Unless you use a super small aperture to shoot, you will not notice the existence of the dust. This is very different from 645z, which has a cover glass right in front of the sensor.
Those who assume that mirrorless collects more dust are probably right on other FF mirrorless. GFX is different. Until you actually own and use one for a substantial time, you are believing the wrong things about GFX.
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Forum: Pentax Medium Format
10-07-2021, 08:36 PM
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What program do you use in your Mac to connect to 645z?
I use Pentax IT2 on my Mac. One thing I found is that when the memory card in 645z has many images, it took extra time for IT2 to connect to 645z. When the card is close to full, the connection time can be so long that one would think the connection fails, but it just takes longer and one just need to wait a bit. This is IT2 + 645z. I don't know about other programs.
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Forum: Pentax Medium Format
08-21-2021, 10:30 PM
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Don't have GFX 100, but have GFX 50R, and 645z, two cameras with identical sensor. After testing a few P645 lenses on 645z and GF lenses on the 50R at large apertures, I would say that I am totally not surprised by what you found. I can't be excited by a 100MP crop sensor from Pentax, unless Pentax also drastically revamp its lenses for 645.
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Forum: Pentax Medium Format
08-01-2021, 10:30 PM
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I don't know about you, but if I am running the business, I would rather have a demand that's so strong that my production cannot keep up, instead of having the product in stock and cannot sell them quickly.
Now, let's put aside the Fuji vs Pentax issues and discuss something else. I have been paying attention to used 645z over the past few years (so I can suggest my friends to buy one when I see a good one showing up). In the Japanese market, a used 645z is getting harder and harder to spot. Usually when a camera model is approaching the end of its life cycle or within a couple of years from the end of production, the prices of the used cameras go down. But on 645z, the used price is not going down by a lot. They just disappear gradually. I don't know what this means.
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Forum: Pentax Medium Format
08-01-2021, 09:59 PM
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I can believe what you said. Many people complain that DPR's reviews are biased against Fuji cameras, but DPR's MF forum is now completely occupied by GFX related threads. It wasn't like this two to three years ago. At that time, you can see probably equal numbers of threads on Fuji, Pentax, Hasselblad MF cameras, and probably a little bit of PhaseOne. Now it's 95% GFX, if not more.
Face it. Many people buy GFX. Pentax needs to put themselves together. I don't want to see my 645z the last MF camera from Pentax.
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Forum: Pentax Medium Format
08-01-2021, 08:47 PM
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It's not photographic film any more. Film has many other applications. For example, from what I heard, Fuji is a dominant supplier for the film covering the flat panel displays. In fact, if you are reading this with a computer, you may be actually seeing through a thin film produced by Fuji right now. Think how many flat panel displays are produced each day in this world. That's highly profitable.
So when Fuji says its film business is profitable, it doesn't imply photographic film is playing a larger role than digital cameras in Fuji's imaging business. It's not the kind of film you had in mind.
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Forum: Pentax Medium Format
07-27-2021, 08:03 PM
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If your company controls both the camera and the lens, then the extra layer of glass may not be a problem. Telephotos with drop-in filters are designed in such a way that the filter glass is part of the optical formula, and using such lenses without a filter can degrade the optical quality. I can suspect that the cover glass in GFX cameras is factored in the lens design, as it sits right behind the rear lens elements.
And even with that cover glass (part of the optical design or not), Fuji lenses perform brilliantly. Fuji wide-angle lenses on GFX is way better than wide-angle lenses on 645z. Now I use my 645z exclusively for long focal lengths. For anything below 110mm, I go to GFX.
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Forum: Pentax Medium Format
07-21-2021, 07:13 PM
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Probably not. I shoot both 645z and GFX. I do astrophotography, which is highly sensitive to dust (after stacking many exposures to boost weak signals in the image). So far my 645z shots almost always shot dust spots no matter how I clean it, while my GFX shots are almost always clean. I suspect the reason is that there is a cover glass right after the lens mount of GFX and quite far away from the sensor. This cover glass keeps the sensor free from dust, and dust on this cover glass would be almost always out of focus since the glass is far away from the sensor.
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Forum: Pentax Medium Format
06-28-2021, 11:49 PM
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I have been doing astrophotography with GFX for more than a year. Its focus-by-wire mechanism does concern me a bit. However, in practice, I haven't noticed any real damage to my final image. For example, this image:
Orion | Fujifilm GFX-50R Fujifilm GF 110mm/F2.0 @ F3.2 two f? | Flickr
is composed from a few long sessions of continuous 5-minute exposures. I haven't not seen hints of focus shift in these sessions. The conclusion I got from my other GFX lenses is similar. I think I still prefer normal lenses (AF or not, IF or not), rather than focus-by-wire ones, but my experience on GFX isn't really bad.
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Forum: Pentax Medium Format
02-10-2021, 12:29 AM
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The different sizes of stars aren’t a distance effect. All stars are practically at infinity to camera lens. They have different sizes in the image because they have different brightness. The point-spread function of stars is never an infinitely small point. Brighter stars have brighter outer parts of the PSF so they appear bigger. The outer part of the PSF is not necessarily caused by diffraction. It can be caused by the atmosphere (scatter and turbulence, depending of the location and focal length), by the lens, or by scattering in the sensor or film (particularly worse on color reversals).
I don’t have experience on the 4-element 200mm lens. However, I had used the newer 200mm. It’s OK on 645z, provided that its lens elements are well aligned. Overall, all Pentax 67 lenses that I had used on 67 film are excellent, but poor on 645z. At least in astrophotography, film is much more forgiving to imperfect optics. These 67 lenses either were not designed to satisfy modern CMOS sensors, or their manufacturing accuracy does allow them to last long enough. The 200mm lens I tried had misaligned lenses and a tilted focal plane. This is easily visible on images of stars. Indeed, many 67 lenses I tried on 645z or FF DSLRs have such troubles, leading me to believe that they should stay with film. So far, among the about 20 various film lenses that I had tried on 645z, GFX50R, or FF, the only one that’s still acceptable (in terms of resolution only) is the Mamiya 645 300/2.8. Everything else failed.
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Forum: Pentax Medium Format
02-09-2021, 03:03 AM
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I did not intend to comment on any lenses that I don't have.
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Forum: Pentax Medium Format
02-08-2021, 10:11 PM
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I happen to have both 645z and GFX (50R). I tried to test all my lenses and store the results on Flickr:
Lenses on 44mm x 33mm Sensors | Flickr
I am an astrophotographer, so I use stars for testing. Stars are ultimate tests of sharpness across the field, and are sensitive to astigmatism, chromatic aberration, etc. They cannot be used to judge distortion and bokeh. The tests are strictly for sharpness.
Of course I can't own all possible lenses. So this is biased to what I have. Based on results from the lenses I have, Fuji wins by miles.
(After looking at my flickr page again, I realize I did not test my Fuji 45mm. However, I had taken a few pictures with it. It's just as good.)
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Forum: Pentax Medium Format
01-30-2021, 09:07 PM
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As a 645z user myself, I also agree that 645z is still very capable. But this is not the problem here. The problem is that the sensor used in 645z was discontinued by Sony quite a while ago. All Pentax can do now is to sell 645z with the sensors that they have in stock. Once they sell out, they have nothing to provide to the market. So Pentax has to start developing a new camera, even if 645z is still very capable. And if they are going to provide a new camera to the market, it has to be awesome, because of the competition from Fuji. So talking about whether 645z is capable is totally irrelevant for Pentax's survival in the MF market.
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Forum: Pentax Medium Format
01-28-2021, 08:25 PM
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I think the minimum Pentax needs to do is to put the 100MP 44x33 sensor in their 645 body and update the sensor-related performance (AF, video, 16bit etc).
Lens wise, the few Pentax 645 lenses I had tried are all extremely sharp in the frame center. They out-resolve the 50MP 44x33 sensor at the center, and they should have no problems on a 100MP one. The unfortunate part is that they are lousy in the corners. I can't say the GFX lenses are sharper in the center, but the GFX lenses definitely generate more uniform image quality over the 44x33 frame.
BTW, I am an astropgotographer. My targets are points all over the field, which are highly demanding for image resolution. I can't comments on other kinds of lens performance, like rendering, bokeh etc.
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Forum: Pentax Medium Format
09-06-2020, 09:51 PM
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Sorry to hear the couple of stories on NEOWISE image ruined by the satellites. But generally speaking, the starlink satellites are low-orbit satellites. They only reflect sun light during the one hour or two (depending on where you are) of evening/morning twilight time. After we are well into the dark, we won't see them easily, because the satellites above us should be also hidden from the sun by earth.
For professional astronomy, the starlink satellites mainly threaten the observations that search for near-earth objects. Those objects can only be easily seen during twilight time. For typical astronomical observations conducted during dark time, starlink can sometimes be annoying, but won't be the end of the world nor end of astronomy.
I think the above applies to amateur astrophotography too. For the kind of astrophotography conducted during twilight (astro landscape, and comet imaging), starlink will be a problem. For other kinds of astrophotography conducted at night, it shouldn't be a major threat. We see many high-orbit satellites every night anyway, and we have ways to remove them from our images.
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Forum: Pentax Medium Format
08-24-2020, 08:56 PM
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The modification replaced the IR-blocking filter with one that allows more deep-red to go through (but still blocks IR). This makes the camera more than 3x more sensitive to red nebulas. It is a must for serious deep-sky photography, but not quite so for wide-field Milky Way shots and astro-landscapes.
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Forum: Pentax Medium Format
08-24-2020, 07:13 PM
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The cost should be manageable if you go with a used one. The real problems are those other than the camera, telescopes, lenses etc.
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Forum: Pentax Medium Format
08-24-2020, 02:36 AM
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I put two links to my gallery in my signature (below the post).
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Forum: Pentax Medium Format
08-23-2020, 11:26 PM
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Loos like you decide to stay with K1. I think this is a wise decision given what you have.
645z is a wonderful camera. It is one of my best investment in astrophotography over perhaps 30 years. However, as others have pointed out, you need a scope with large image circle to do justice to 645z. Not many scopes can do that, and definitely not a GSO. (A heavily retrofitted GSO can, perhaps.) Indeed, even with an FF camera, the GSO may have issues. You will need a good field flattener or large focal reducer on a GSO RC to produce a flat field for an FF camera, and this would required a focuser much better than what GSO offers in its standard package.
For astrophotography without a telescope, 645z is not a perfect choice either. The camera is really excellent in terms of sensor performance, but lenses from Pentax are just not good for astrophotography. (I try to be polite here. So I just say they are "not good.") First of all, the apertures are too small to start with, as you probably had also realized. Then, almost all of them have terrible coma/astigmatism in the corners and require severe stopping down of the aperture. To take really decent pictures, you will need to go to a dark place and integrate for hours to overcome the small aperture+stopping down. I see that you have an equatorial mount. So in principle, you can do that. But that's really not the best thing to do. You will be torturing yourself. Use an FF camera plus a good large-aperture lens (like those from Sigma) and you will be in a much better position to take stunning photos, and this will cost much less.
If you do have a telescope that can cover 645z's sensor well, I would say go for it. You won't regret. For everything else (astrophoto-wise), don't.
You are welcome to check my gallery. There are many 645z astrophotos.
---------- Post added 08-23-20 at 11:43 PM ----------
There is at least one off-the-shelf 645z adapter:
M65x1 female thread to Pentax 645 camera mount adapter
All you need now is an adapter with M65x1 thread and whatever attachment required by your 2.7" focuser.
Note that you will also need a field flattener for your refractor. A 7" refractor with a 2.7" focuser should be able to fully illuminate the sensor of 645z, but the stars won't be good in the corners as the focal surface is usually curved. Once you have a flattener, you need to pay attention to its back focus.
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Forum: Pentax Medium Format
03-11-2020, 05:45 PM
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Right. Not just that image, all side-by-side test images I took with the GFX50R are more noisy than 645 ones. They use the same sensor. So I suspect that the difference comes from the continuous live view, which keeps the sensor constantly working, and therefore generates lot of heat from the sensor and other internal circuits. Unfortunately I haven't had enough tests to verify that heat is indeed the cause of the extra noise in GFX.
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Forum: Pentax Medium Format
03-10-2020, 09:08 AM
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Did not see this thread before. I have an RAF adapter for P645. It fits the camera nicely, without problems, although I have never really needed to use it.
My telescope has a P67 adapter made by the telescope manufacture. Then I use Pentax's own 67-645 adapter to hook up my 645z. Earlier Stevein mentioned about Astrobin search results. The majority of 645z images you can find on Astrobin was taken by me. And this is my Astrobin gallery.
To be able to to use 645z on a telescope, the adapter is just one of the equations. There are two additional requirements, both of which are more difficult to meet than getting an adapter:
1. The telescope needs to be able to project a flat image circle that's large enough for a 44x33mm sensor. Not many telescopes can do this. It typically requires a large focuser, and a large, dedicated corrector lens (focal reducer, field flattener, or coma corrector, depending on the type of telescope). Most telescopes in the market are designed for APS-C or FF, and they don't have a focuser and a corrector lens large enough for P645.
2. The optimal focus point should be far away from the last lens element of the corrector lens, far enough to accommodate the humongous 71 mm flange-back distance of P645 plus whatever length for the adapter. Among all 645 cameras, P645 has the largest flange-back distance, and not just large, unreasonably large. Pretty much only telescopes that are designed for P67 (very few) can offer this kind of back-focal distance for P645. If we are talking about Fuji GFX here, things will look much better. There are some very nice telescopes that can accommodate GFX but cannot accommodate P645, because of the very stringent requirement on back-focal distance.
The OP wanted to hook up his 645D to C4.5. There is just no hope he can do it, and no point for him to do it. C4.5 does not have the kind of large back-focal distance for P645. Even if it somehow magically has, its focuser is way too weak to support 645D's weight. Even if the weight is not an issue and even if it can reach focus, C4.5 cannot illuminate a 44x33mm area with good image quality from center to corners. If it is an 8inch Newtonian instead of 4.5inch, then it starts to look feasible. It is possible to find a strong focuser to be put on an 8+inch Newtonian with a coma corrector that can accommodate P645 (TV BIG Paracorr).
645z is absolutely a powerful camera for astrophotography. Unfortunately only few telescopes can go along with 645z.
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Forum: Pentax Medium Format
02-25-2020, 11:26 PM
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I think the current 645z is great in many ways, but can also benefit from many improvements like those mentioned in this thread. The real problem I see is that, Pentax just doesn't have the resource to do it. Just maintaining their FF and APSC lines plus a couple of new lenses every few years (not including those made by Tokina and Tamron with Pentax marks) already seems difficult enough for them. It will be a big surprise to me if they can do any major upgrade to the 645z line.
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