[batmobile]

I am incredibly glad the 28-45 is SR, as it allows me so much freedom and working speed. I shot most of my landscapes in Iceland hand held, as I do everywhere and the 645z 28-45 combo was phenomenal.I used the 80-160 a lot too and am waiting for that lens to be replaced with a new SR version. My 80-160 A is sometimes amazing and sometimes good, with slight softness on the left at the very long end. The other benefit of new designs is that there is better QC and tolerances. The FA and A lenses were not built with the demands of 51MP.

If the new lenses are anything like the 28-45, I will get the 45-85 and 80-160. Both should be more compact and lighter than the 28-45 as wides are very demanding when it comes to size compromise.

FWIW I think Pentax/Ricoh very much knows what its doing with lens design. The 28-45 shames most ultra-wide angle zoom FF lens out there on a per pixel basis, with the exception of the new Canon 16-35 F4 L and possibly the Nikkor 14-24 (which isn't dramatically lighter and has no stabilisation). The 18.3mm lens on the GR V is one of the best lenses I have ever used, period and I have lots of Leica, Zeiss and L glass.

[shuttles12000]

I'd love to see a zoom lens covering 30-112mm (ie 24-90mm in Full Frame terms).
I use that focal length range for 90% of my shoots

[Chris Giles]

I'd like to see a 3.2 constant aperture zoom. I know 2.8 is physically impractical but 4.5 is too slow for me. (I still have the zooms). If they launch them at current zoom prices there isn't enough draw for me to make a purchase.

[Kolor-Pikker]

I'd like to see a 3.2 constant aperture zoom. I know 2.8 is physically impractical but 4.5 is too slow for me. (I still have the zooms). If they launch them at current zoom prices there isn't enough draw for me to make a purchase.

This is too rough to be called scientific, but f/4.5 on 33x44 is roughly "equivalent" to f/2.8 on 36x24mm, both in terms of depth of field and light gathering ability. If we go by the square root system used for aperture size (f/1.4/2.0/2.8), then 33x44 is around 1 & 1/4th stops "bigger" than 36x24mm, so the light loss incurred from the smaller aperture is offset by the larger light-gathering surface area.

What this means is in practical terms, is that the 645Z should be as sensitive at ISO1000 as a 35mm camera with the same sensor technology is at ISO400, assuming we normalize the output size of both. Looking at a 51mp image at 100% yields a much bigger enlargement than at 22/36mp, and may give a false impression of how much noise you're actually dealing with.

If Pentax ever releases a full-frame 645, the gap will grow to favor the f/4.5 lens as the sensor will be more sensitive than the light loss incurred.

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Last edited by Kolor-Pikker; 05-26-2015 at 12:03 PM.

[Chris Giles]

This is too rough to be called scientific, but f/4.5 on 33x44 is roughly "equivalent" to f/2.8 on 36x24mm, both in terms of depth of field and light gathering ability. If we go by the square root system used for aperture size (f/1.4/2.0/2.8), then 33x44 is around 1 & 1/4th stops "bigger" than 36x24mm, so the light loss incurred from the smaller aperture is offset by the larger light-gathering surface area.

What this means is in practical terms, is that the 645Z should be as sensitive at ISO1000 as a 35mm camera with the same sensor technology is at ISO400, assuming we normalize the output size of both. Looking at a 51mp image at 100% yields a much bigger enlargement than at 22/36mp, and may give a false impression of how much noise you're actually dealing with.

If Pentax ever releases a full-frame 645, the gap will grow to favor the f/4.5 lens as the sensor will be more sensitive than the light loss incurred.

Gotcha. But it's also about focusing speed to me. Seems slower with the zooms (more hunting).

[Pål Jensen]

This is too rough to be called scientific, but f/4.5 on 33x44 is roughly "equivalent" to f/2.8 on 36x24mm, both in terms of depth of field and light gathering ability.

No one is buying a 645 in order for it to gather the same amount of light as a 35mm camera. The point is to gather more light while maintaining exposure. That is why F:4.5 is equivalent to F:4.5 regardless of format, just like the lens manufacturers print on their lenses regardless of format...

[Kolor-Pikker]

Gotcha. But it's also about focusing speed to me. Seems slower with the zooms (more hunting).

Screw-drive lenses do seem to hunt a bit more, even though they focus as fast, perhaps the ultrasonic motor on the new lenses will be faster and more accurate?

No one is buying a 645 in order for it to gather the same amount of light as a 35mm camera. The point is to gather more light while maintaining exposure. That is why F:4.5 is equivalent to F:4.5 regardless of format, just like the lens manufacturers print on their lenses regardless of format...

It's about how we creatively use the hardware than what's printed on the tin. A lens can be 55mm f/2.8, but if it has the FoV and DoF of a 43mm f1.9 on small format, I'd still have framed the subject the same way if there was such a lens. With sensitivity, if ISO400 looked good on a 13x19" print from my 5D2, I would expect the same result from the Z at ISO2000+.

Depth of field if a very important detail to consider when comparing equivalent exposures because f/4 on MF is shallower than f/4 on 35mm, so you need to stop the MF camera down to around f/6.3. If we kept the aperture the same then yes, the 645Z gathers more light, but it's not how the camera would be used.

Light gathering performance between formats has a cutoff point where you're comparing two different things. Around and below ISO400, the 645Z will give you a superior image to most other camera sensors, while past ISO400 it's about how much less noise the 645Z has than other cameras.

In a best case scenario, the 645Z doesn't perform worse than a small format camera at high ISO if you're trying to maintain the same DoF, which is a big deal, since before, every medium format camera would have been significantly worse.

In this respect, I bought the 645Z exactly because it can gather the same amount of light as a 35mm camera at high ISO - while also having the benefit of a very clean and high dynamic range image at low ISO.

Edit: The simplest way to imagine this, is that as long as the 645Z is set to use 1.3 stops more ISO and smaller aperture than an equivalent 35mm camera, both will be equal in practical use, the only time the 645Z pulls ahead is at ISO100 since the D800 would need ISO35 to compete. Non of this takes into consideration things like resolution of course.

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Last edited by Kolor-Pikker; 05-27-2015 at 01:31 AM.

[rfkiii]

No one is buying a 645 in order for it to gather the same amount of light as a 35mm camera. The point is to gather more light while maintaining exposure. That is why F:4.5 is equivalent to F:4.5 regardless of format, just like the lens manufacturers print on their lenses regardless of format...

I used to make similar statements whenever equivalence came up on forums dedicated to FF cameras. Usually, these discussions concerned FF vs. APS-C and as a dyed-in-the-wool FF shooter, I saw little need for cluttering my thinking with this information. However, now that I am using a different format, I see the fascination. Thinking in terms of a format that has been long ingrained helps me get acclimated quicker to this format especially in terms of DoF and FOV. But, essentially, I use different formats for their un-equivalence.



---------- Post added 05-27-15 at 04:51 AM ----------

I'd like to see a 3.2 constant aperture zoom. I know 2.8 is physically impractical but 4.5 is too slow for me. (I still have the zooms). If they launch them at current zoom prices there isn't enough draw for me to make a purchase.

An F4.5 645 lens made for the full frame 645 format that will be equivalent to f3.5 in terms of FOV/DoF on the 645z "crop camera" which in turn is equivalent to an f2.8 on FF 135 format.

[Pål Jensen]

It's about how we creatively use the hardware than what's printed on the tin. A lens can be 55mm f/2.8, but if it has the FoV and DoF of a 43mm f1.9 on small format, I'd still have framed the subject the same way if there was such a lens. With sensitivity, if ISO400 looked good on a 13x19" print from my 5D2, I would expect the same result from the Z at ISO2000+..

Exactly. It is about the use of the hardware. This use is dictated by the law of reciprocity where the only equivalency is exposure. DOF does not enter the definition of either focal length, angle of view or aperture.

The simplest way to express the DOF differences is to state that larger format need to shoot at a slower shutter speed at the same DOF and ISO than a smaller format. That's all there is to it. It is completely up to the photographers whim whether he want to do that, or increase the ISO, change aperture or shutter speed or whatever. There's no rules involved except the law of reciprocity.

The DOF equivalency between a 55/2.8 and a 43/1.9 is a best a gross simplification. This is because DOF is not solely dependent on focal length and aperture but on focusing distances and, hence, subject magnification; it gives no meaning stating DOF without stating the focusing distance and/or subject magnification. The lenses mentioned above may well have similar DOF wide open at, say, 5 meters, but they will be totally different at close focusing distances where the smaller format lens will have indeed thinner DOF wide open (and even give a different perspective!). Provided that both lense have the same minimum aperture, the smaller format lens will have a larger range of DOF to choose from. Those lenses are simply not DOF equivalent.
In addition, many images are DOF insensitive; eg like at infinity. DOF is simply not suitable a parameter to equalize lenses. Exposure is and that is whats being done industry wide.
There's no particular reason for two lenses with the same angle of view and max aperture on different format must have the same DOF, except as a point of view.

It is better to accept that formats are not truly DOF equivalent and use them to their advantages. And that is what most photographers do.

[Chris Giles]

Hello, just to repeat, it's the speed of the autofocus that I care about. A wider aperture is usually easier for the AF system to attain focus. I'd probably still shoot a smaller aperture.

Couldn't give a fig about the depth of field. Not in the slightest. Just faster focus so I miss less shots.

[Kolor-Pikker]

It is better to accept that formats are not truly DOF equivalent and use them to their advantages. And that is what most photographers do.

Ironically it's the larger formats that people tend to shoot stopped down, even though they provide the more pleasing out of focus rendering, MF users mostly photograph either landscape, architecture or in the studio. And good luck finding anyone shooting large format or tech cameras wide open.
Meanwhile, users of small-sensor cameras just can't get enough of fast glass, all the way up to f/0.95 in some cases. And why was the speed booster invented then, if people don't desire equivalency?

Hello, just to repeat, it's the speed of the autofocus that I care about. A wider aperture is usually easier for the AF system to attain focus. I'd probably still shoot a smaller aperture.

Couldn't give a fig about the depth of field. Not in the slightest. Just faster focus so I miss less shots.

Sorry, but I'm afraid this topic has gone way past your stop and all the way to narnia. Tends to happen.

AF systems detect the phase difference between two images seen though the lens, and the amount of separation between them is dependent on how wide the aperture is, but since the AF unit is the same size as in other Pentax SLRs, the f/4.5 aperture is treated just like a lens of the same kind on a K-series camera.

The only real way to fix this is to make a purpose-built AF unit for the 645 format that can cover more of the frame, as this would improve focus accuracy globally across all lenses, but knowing the tendency of these things, Pentax will probably just take the AF unit from their upcoming full-frame camera and use it in the next 645. It would be a step forward in any case, but they really need to figure out how to make bigger AF sensors. For the S 007, Leica will likely just continue making one really big center AF point to focus on accuracy, which is the right way to go I think, they can always add more points once they have it perfected.

[Lacunapratum]

As you can hear, there are different types of users. I'd personally prefer some fast and high quality primes over bulky slow zooms that may nevertheless represent that latest in optical technology.

I'd like to see a 25mm replacement (possibly even wider), an updated 35mm, a fast portrait (120mm f/2; yes, 120mm, not 100mm), a 180mm macro telephoto, and an updated 300mm f/4. And a 35mm shift lens. Six lenses only . I am easy . Could care less about the zooms. It's medium format. You can move or crop.

[gavincato]

I wouldn't be able to get my wallet out fast enough for a modern f/2 tele lens.

[2351HD]

I agree on the ultra wide prime.

The problem with the 25 was that it was made for full 645, not DA. It they were to remake a 24mm in DA, not only could it be better quality but also smaller. Take out the inbuilt filter and supply it with a front adapter that accepts screw in filters and can attach grads etc.

[batmobile]

For the wide prime, considering the existence of the 28-45, 22mm would be about right IMO.