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06-12-2019, 01:40 PM   #16
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QuoteOriginally posted by kaseki Quote
One would expect that a Fresnel lens, even a perfectly constructed one, would have higher aberrations than a smooth surface lens of the same base curvature, and this would be further degraded off-axis where the side walls of each annular section are included in some of the light paths. Computational post-processing may be able to address much of this, but (a), surely it is not presently in all cameras that might use the Fresnel lenses, and (b), even with extravagant processing, there would be some residual effects that might show up as haze or blur. Without seeing actual measurement results showing Fresnel lens effects can be made negligible, I wouldn't myself recommend Pentax leap into that pit. And my Pentax systems have the most weight to lose. [Obligatory joke]

In the above comment, I want to note that I am not considering a diamond turned lens to be a Fresnel lens, because diamond turned lenses have annular cut widths smaller than the wavelength of the light being refracted, thereby minimizing in-band scatter, and in their case I think the summation integral of the point spread function is pretty much additive into the desired circular aperture PSF, at least insofar as pixels 10X the wavelength can measure.
Everything has a trade off. I just am looking for something that will maintain decent image quality while leaving size manageable. I just thought that the reviews of the Nikon 300mm f4 didn't show any major down side and did show a significant decrease in size.

06-12-2019, 06:03 PM   #17
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I will restrain my unbounded curiosity until I can research the topic more thoroughly than the half-hearted stab I made today.
06-12-2019, 10:47 PM   #18
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Im just waiting for the release of the DFA*85, and see if i can afford it... if not, those FA*85 will drop in price,,as far as this lenses, they're out of any use for me, maybe only to brag about have a very big lens (i more inclined to portrait, and the DFA*70-200 (and DFA*50 and FA77ltd) is more than enough
06-13-2019, 02:13 AM   #19
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I'm really grateful so many people are being seduced (Oooooh, Matron !) by all the marketing hype. Once they have assuaged their purchasing desires, their old kit will come on the market at prices I can afford, and I think it unlikely that any improvement in IQ will be worth what they are spending.

06-13-2019, 02:42 AM - 1 Like   #20
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QuoteOriginally posted by biz-engineer Quote
I guess Nikon have found ways to work around that.
Yes, but it's in their Capture NX-D RAW processing software: PF Flare Control.
06-14-2019, 04:16 AM   #21
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QuoteOriginally posted by normhead Quote
When you've heard folks argue they didn't need TTL metering or Auto-aperture and look at the things people say you "need" today, like 60 fps etc, you have real perspective on what a load of nonsense modern marketing is for a lot of shooters.

No one today would dream of introducing a new model without TTL or auto aperture, yet at one time they were deemed ignorable by brand owners to whom they were not available. And now folks claim 4 fps isn't good enough.

We used to get a frame every 10 seconds. And it was good enough.

Read the light meter, set the aperture on the lens and shutter speed on the camera, check the DoF guide, calculate your hyperlocal, recheck the light to make sure it hadn't changed, take the picture.
Thanks Norm,
That still describes me with a KP or a K3 or K5 or K7 or Q or.................
06-14-2019, 05:35 AM   #22
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QuoteOriginally posted by lukulele Quote
Thanks Norm,
That still describes me with a KP or a K3 or K5 or K7 or Q or.................
I have two modes these days... first, get something, snap off a few frames to make use you have something to work with. Then set up and do the "prefect" shot if you have time. Modern cameras make the first part really easy. The second part, optimizing your exposure for your scene still takes time.

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