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Forum: Pentax News and Rumors
06-20-2016, 01:03 AM
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Equivalency is a prerequisite for comparability. You don't have to compare. But if you do, you should have equal expressions on each side of the equation.
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Forum: Pentax News and Rumors
06-18-2016, 04:52 AM
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With comparatively low market share it doesn't make sense to have very many overlapping lenses. I don't see the need for the f/4 zoom line that Na Horuk mention unless it offers some other unique features.
Personally I would like to have a D-FA 28-300 f/3,5-6,3 WR as an allrounder. Both for those times its to fiddly or time consuming to change lenses, and for those times I want to carry less. Then I will supplement it with primes for other times.
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Forum: Pentax News and Rumors
06-04-2016, 09:39 AM
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The basis was johnmflores quote:
K-1 crop mode was not mentioned, but this obviously hints about exposure differences between APS-C and FF in general. The theory is clear, FF have about 1 stop lower noise then APS-C if you use the same aperture number. Now, if you set the FF system back with 1 stop smaller aperture, that noise advantage is lost. Turning theory into practice, we talk about the DA* 16-50mm f/2,8 zoom on K-3II versus the patented 35-80 f/4 zoom on K-1. Its not an exact match but close enough that large parts of the zoom ranges gives equal field of view. The DA* are designed for APS-C and does not work well on K-1 in FF mode. The 35-80 f/4 patent states FF image circle. We are not talking about a bag of f/2,8 FF lenses used on a crop camera and comparing it to f/4 FF lenses on a FF camera. We are comparing lenses that are designed for the sensor they are used on. Lenses are designed to have a micro contrast suitable for the sensor size its supposed to be used on. The same goes for CA.
The video shows that telephoto compression changes with field of view. Just like I said. But he only changes field of view in one of the two ways possible. By changing the focal length and not by changing sensor size. In post #60 you claimed that the bag of f/4 zooms would give more telephoto compression. Maybe I misunderstood you. There is two possibilities:
1. You claim that FF shooters choose narrower FoV (different composition) then APS-C shooters in the same situation. That would be absolutely ridiculous. OR
2. You claim that telephoto compression depends solely on focal length, not FoV or sensor size. That is absolutely wrong.
So, given my possible misinterpretation, was your claim 1. absolutely ridiculous or 2. absolutely wrong?
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Forum: Pentax News and Rumors
06-04-2016, 09:27 AM
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The basis was johnmflores quote:
K-1 crop mode was not mentioned, but this obviously hints about exposure differences between APS-C and FF in general. The theory is clear, FF have about 1 stop lower noise then APS-C if you use the same aperture number. Now, if you set the FF system back with 1 stop smaller aperture, that noise advantage is lost. Turning theory into practice, we talk about the DA* 16-50mm f/2,8 zoom on K-3II versus the patented 35-80 f/4 zoom on K-1. Its not an exact match but close enough that large parts of the zoom ranges gives equal field of view. The DA* are designed for APS-C and does not work well on K-1 in FF mode. The 35-80 f/4 patent states FF image circle. We are not talking about a bag of f/2,8 FF lenses used on a crop camera and comparing it to f/4 FF lenses on a FF camera. We are comparing lenses that are designed for the sensor they are used on. Lenses are designed to have a micro contrast suitable for the sensor size its supposed to be used on. The same goes for CA.
The video shows that telephoto compression changes with field of view. Just like I said. But he doesnt change the field of view wit
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Forum: Pentax News and Rumors
06-04-2016, 02:27 AM
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In crop mode? Well, we should start a new thread about that. :) Real world comparison between K-1 crop mode and various Pentax APS-C models with the same lenses. It would be an interesting investigation and read. Before testing I would assume that K-5IIs and K-1 crop mode perform quite close and slightly better then K-3/K-3II on noise.
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Forum: Pentax News and Rumors
06-04-2016, 12:34 AM
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I think we might have talked about slightly different things. Looking back, johnmflores talked about K-3II vs K-1. I was talking about APS-C vs FF in general, like in K-1 crop mode vs FF mode. I'm not sure if there is a noise difference or how large it would be between the the K-3II and K-1 crop mode, but if we take sensor differences out of the equation, like K-1 crop mode vs FF mode, then f/4 on FF should equal f/2,8 in crop mode in terms of noise. Of course except when the ISO levels hit their extreme limits and cant be changed accordingly or comparing apples to oranges scenes. In this context there is no noise benefit from using f/4 on FF compared to f/2,8 in crop mode.
In my vocabulary sharpness and resolution are synonyms, and thus mentioned twice.
The claim of less perspective distortion (more telephoto compression) is a clear misunderstanding of the concept from Silver-Surfer. This is entirely a property that depends on field of view. Sensor size and focal length is just underlying factors to what FoV you get. Please don't roll eyes and tell others to do more research when you should have done that yourself. Please look up telephoto compression and what influences it.
As for CA, I said I don't know if there is a general advantage to having larger sensors. You can compare vastly different sensor sizes with a selection of lenses that was designed for their size and see that CA can be well controlled with all sizes. And badly controlled with all sizes. Its a lens design choice for the intended quality and price.
In other words, 5 advantages condensed down to 1 advantage, 1 uncertain, 1 redundant and 2 wrongs.
Please try to discuss this in a good manner in the context of the topic. If you think I need some explanation, please explain. I'm here to socialize around my main interests, and hopefully learn more, not to get comments like I should do more research on photography in general before posting, without any explanation.
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Forum: Pentax News and Rumors
06-03-2016, 02:01 PM
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Can you just tell me what you disagree with and explain? We are not making progress with this unspecific nonsense.
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Forum: Pentax News and Rumors
06-03-2016, 01:43 PM
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Forum: Pentax News and Rumors
06-03-2016, 01:18 PM
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@Silver-Surfer: I'm just happy to help. If you still wonder about something, just ask.
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Forum: Pentax News and Rumors
06-03-2016, 09:17 AM
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Resolution - I agree
Less noise - Disagree, using f/2,8 on APS-C yelds as low noise as f/4 on FF, given the same shutter speed, scene and so on.
Sharpness - You already mentioned that
Narrower CA - I'm not sure that holds true as a general property.
More compressed images - That does not hold true. Telephoto compression is a function of field of view. Given that you choose lenses with the same FoV, the compression will be the same.
Edit: Try googles translation of the patent. It will save you years of study to get to that quality level of Japanese.
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Forum: Pentax News and Rumors
06-01-2016, 02:17 PM
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The patent describes a length of 160mm at the shortest, from sensor to the front element. If the patent don't describe the patent, what does it describe then? Its the patent that are the subject of this thread, not something totally unrelated.
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Forum: Pentax News and Rumors
06-01-2016, 01:48 PM
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Why do you still discuss like it is a small lens? Haven't we already figured out that it will be quite large? (larger then D-FA 28-105)
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Forum: Pentax News and Rumors
06-01-2016, 06:33 AM
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Image height seems to always mean radius of the image circle in these patents. 21,64 mm corresponds to the distance from the center to the corner of the sensor, 21,633 mm (if we assume the K-1 sensor are exactly 36 x 24 mm, which probably only are an approximation).
Where did you get the 38 mm number from? The K mount focal flange distance is 45,46 mm and the K-1 mirror is lifted out of the way in a special move that doesn't leave much headroom for protruding rear elements.
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Forum: Pentax News and Rumors
06-01-2016, 05:15 AM
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This is a very long lens for its specs. Far from any limited philosophy.
The lenght is probably the axis from the front element to the sensor. If the drawing are in scale, the front element should be about 55mm across and the distance from the rear element to the sensor about 48 mm, which seems very reasonable for the K mount focal flange distance. It would come in conflict with the mirror in a 645 camera.
The size doesn't make any sense to me. I guess something are lost in translation. Maybe its a 35-80 mm f/1,4 lens in stead of f/4,1 :p
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