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10-16-2021, 03:34 AM - 1 Like   #181
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QuoteOriginally posted by acidbabe Quote
is the lans cap included or do the charge you €50 extra for that one?
Pentax includes lens caps with all of their lenses.

10-16-2021, 03:45 AM   #182
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QuoteOriginally posted by acidbabe Quote
is the lans cap included or do the charge you €50 extra for that one?
'Included Accessories
Lens Cap O-LW74A, Lens Mount Cap K, Lens Case P80-150
'

HD PENTAX-D FA 21mm F2.4ED Limited DC WR :An ultra-wide-angle single-focus lens for use with PENTAX K-mount full-frame digital SLR cameras?RICOH IMAGING
10-16-2021, 04:02 AM   #183
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For equivalence you'd have to compare it with this one although it has F4 aperture equivalence. It would need to be F1.6 to have aperture equivalence.

Last edited by D1N0; 10-16-2021 at 04:14 AM.
10-16-2021, 04:36 AM   #184
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QuoteOriginally posted by D1N0 Quote

For equivalence you'd have to compare it with this one although it has F4 aperture equivalence. It would need to be F1.6 to have aperture equivalence.
While we are at that, I really would want this lens to be overhauled and brought to high resolution APS-C sensor standards... and here I mean sterile technical corner to corner sharpness. The system needs a wa-lens for documentation photography.

10-16-2021, 04:38 AM - 3 Likes   #185
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QuoteOriginally posted by D1N0 Quote

For equivalence you'd have to compare it with this one although it has F4 aperture equivalence. It would need to be F1.6 to have aperture equivalence.

No (please don't get me started!). There's no such thing as aperture equivalence, except the same aperture (ie 2.8 = 2.8 regardless of format). It is the same DOF wide open you mean. That may or may not be an issue depending on your taste, the subject and what you want to achieve...
10-16-2021, 04:57 AM   #186
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QuoteOriginally posted by D1N0 Quote
For equivalence you'd have to compare it with this one although it has F4 aperture equivalence. It would need to be F1.6 to have aperture equivalence.
If you say "for archieving exactly the same image", you'd be right.
Otherwise focal lenght equivalent relates to viewing angle and aperture to physical transmission (t-stop).
So there is no aperture equivalence, since sensor format doesn't affect the aperture of the lens. Only the effects of the aperture on blur and DoF related to equivalence would be correct.
10-16-2021, 05:16 AM - 1 Like   #187
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QuoteOriginally posted by Pål Jensen Quote
No (please don't get me started!). There's no such thing as aperture equivalence, except the same aperture (ie 2.8 = 2.8 regardless of format). It is the same DOF wide open you mean. That may or may not be an issue depending on your taste, the subject and what you want to achieve...


I got you started already It's called equivalence for a reason. It is not about the F number it is about similarity in the actual image. A 14mm lens will have wider DOF than a 21mm lens at the same F-number, so for narrower DOF it will need a larger aperture. Also there is the total amount of light on your sensor. APS-C sensors are smaller so you also need a larger aperture opening to allow more light in. (For correct equivalence you would need the T-stop, not the F-stop, but then DOF and Light gathering will no longer have the same equivalent aperture value).

10-16-2021, 05:24 AM - 1 Like   #188
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So after >20 years Pentax expand the full format lens range with a DFA 21/2.4 limited.
I'm looking very positive at that, and might buy the lense to replace my Sigma 20/1.8, and becsuse I have the other limited.
But now I'm wondering if Pentax might also expand the FF limited range in the other end...something longer than 77mm, but shorter than 200mm. A 100mm limited, or 105mm limited....or a FF 135mm limited. Or if they like unusual focal lengts (like 31, 43, 77mm): a 120mm limited (the K mount line included a 120mm). I don't believe in a 100mm limited since they produce a 100mm macro. But something in the range 120-135mm would complement the DFA limited range very well. Today it's the FA 135/2.8 that plays that role, but it's been out of production for about 25 years. I'm just speculating. But the new DFA limited tell us that Pentax intention is that DFA limiteds remain a part of their FF strategy...it's not just an old legacy that they keep to fill the FF lense range...it's more than that. And that might result in more new DFA limiteds....maybe a DFA limited zoom, like in the APS-C limited lense range.
10-16-2021, 05:59 AM - 1 Like   #189
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QuoteOriginally posted by D1N0 Quote
I got you started already It's called equivalence for a reason. It is not about the F number it is about similarity in the actual image. A 14mm lens will have wider DOF than a 21mm lens at the same F-number, so for narrower DOF it will need a larger aperture. Also there is the total amount of light on your sensor. APS-C sensors are smaller so you also need a larger aperture opening to allow more light in. (For correct equivalence you would need the T-stop, not the F-stop, but then DOF and Light gathering will no longer have the same equivalent aperture value).
The choice of format is not about getting exactly the same image. By insisting on using FF DOF wide open as benchmark and APS as benchmark for the "similar" image, you are not only being inconsequent but are simply manipulating the law of reciprocity to suit your argument. Who can say what DOF is most desirable at 94 degree angle of view and F:2.8? This is 100% subjective.

The fact is that DOF is different wide open for different formats for the same angle of view because you use different focal lengths to obtain the same angle of view.
Different formats will never be truly equivalent for this reason, and particularly not if you want to maintain the larger formats advantage in image quality (all else equal) - something most people are prone to want.
It is not about the same amount of total light because only a madman will buy a FF camera in order for it to perform like an APS body. We already know that an FF body can function as a APS body, and that is all what this "equivalence" really proves; the obvious in an extremely roundabout way, and confuse a lot of people in the process unnecessarily.

Last edited by Pål Jensen; 10-16-2021 at 06:13 AM.
10-16-2021, 06:50 AM - 1 Like   #190
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QuoteOriginally posted by Pål Jensen Quote
The choice of format is not about getting exactly the same image. By insisting on using FF DOF wide open as benchmark and APS as benchmark for the "similar" image, you are not only being inconsequent but are simply manipulating the law of reciprocity to suit your argument. Who can say what DOF is most desirable at 94 degree angle of view and F:2.8? This is 100% subjective.

The fact is that DOF is different wide open for different formats for the same angle of view because you use different focal lengths to obtain the same angle of view.
Different formats will never be truly equivalent for this reason, and particularly not if you want to maintain the larger formats advantage in image quality (all else equal) - something most people are prone to want.
It is not about the same amount of total light because only a madman will buy a FF camera in order for it to perform like an APS body. We already know that an FF body can function as a APS body, and that is all what this "equivalence" really proves; the obvious in an extremely roundabout way, and confuse a lot of people in the process unnecessarily.

The choice of format is a given. If you want to know what lens you would need to get approximately the same image on a different format, you need to look at equivalance. I am breaking no laws. You just don't wish to see it my way so you blame me for being inconsequent while your reasoning is illogical. You are even trying to make me out a law breaker now, like I owe you something.
10-16-2021, 07:03 AM - 5 Likes   #191
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QuoteOriginally posted by D1N0 Quote
I got you started already It's called equivalence for a reason. It is not about the F number it is about similarity in the actual image.
Absolutely wrong. Equivalence is only about the field of view. Only FF promoters claim it's about depth of field.

The simple fact is, ƒ2.8 on a 100mm lens on APS-lens will have the same field of view and use the same exposure value as ƒ/150 2.8 on FF. Two variables are used and are addressed in equivalence formula. As far as I know, there is no formula that determines equivalent depth of field. Maybe you can point us to one if you think it's a thing. But as far as I know, DoF is not adressed as a variable in any equivalence formula. A DoF equivalence would have to be a completely different formula, (and isn't even possible, if you look at FoV, transmitted light and DoF, any equivalence is physically impossible, you cannot maintain the amount of light, the aperture and DoF. It simply will not resolve.) No one has bothered with that, as it would be so pointless. Not everything can be simplified to fit the need to justify DoF as an important factor in lens selection, as hard as the proponents of elective DoF would try and make it so. The discussion has been going on since the 30s but, most people are concerned with getting enough DoF.

The whole denigration of small sensors as only equivalent to ƒ/8 or whatever is one of the most misleading misuses or abuses of limited information to promote bias ever inflicted on photography.

That my ZS100 achieves the DoF at 2.8 that an FF does at ƒ/8 or whatever, is a wonderful thing especially for those photographing in low light. The achievement of wide DoF at low light values completely exceeds any possible advantage in producing narrow DoF images. In technical terms, compared to larger format camera, small sensor DoF is an amazing technological achievement. Similar resolution, superior DoF, in much lower light.

ƒ/stops are calibrated for exposure. Not DoF. Full stop, end of discussion.

Last edited by normhead; 10-16-2021 at 07:47 AM.
10-16-2021, 07:26 AM   #192
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This is great news, it's a good offering to the system. People complaining about the price... it's an investment grade piece of glass, it's what they cost new.
10-16-2021, 07:33 AM   #193
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QuoteOriginally posted by Douglas_of_Sweden Quote
So after >20 years Pentax expand the full format lens range with a DFA 21/2.4 limited.
I'm looking very positive at that, and might buy the lense to replace my Sigma 20/1.8, and becsuse I have the other limited.
But now I'm wondering if Pentax might also expand the FF limited range in the other end...something longer than 77mm, but shorter than 200mm. A 100mm limited, or 105mm limited....or a FF 135mm limited. Or if they like unusual focal lengts (like 31, 43, 77mm): a 120mm limited (the K mount line included a 120mm). I don't believe in a 100mm limited since they produce a 100mm macro. But something in the range 120-135mm would complement the DFA limited range very well. Today it's the FA 135/2.8 that plays that role, but it's been out of production for about 25 years. I'm just speculating. But the new DFA limited tell us that Pentax intention is that DFA limiteds remain a part of their FF strategy...it's not just an old legacy that they keep to fill the FF lense range...it's more than that. And that might result in more new DFA limiteds....maybe a DFA limited zoom, like in the APS-C limited lense range.
I believe they will replace the three original FA Limiteds in due course. Maybe in a few years. I don't think we will see lenses longer than 100mm as Limiteds. I think they want to keep them reasonably compact.
10-16-2021, 07:33 AM   #194
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QuoteOriginally posted by Rondec Quote
Pentax includes lens caps with all of their lenses.
QuoteOriginally posted by Mistral75 Quote
Thank you guys!
10-16-2021, 07:50 AM   #195
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QuoteOriginally posted by normhead Quote
Absolutely wrong. Equivalence is only about the field of view.
Equivalence can be used for absolutely any comparsion. $100 is equivalent to $86,21 (Norm: "You are wrong $100 is $100 and nothing else" )
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