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02-23-2017, 04:24 PM   #31
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Always amused by people saying no need for f2 / f2.8 in portraiture.

02-23-2017, 09:45 PM   #32
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QuoteOriginally posted by Ed Hurst Quote
I understand entirely and you are probably right. But I'd like to see Pentax surprise us and do it.

It could be that your standards are higher than mine, but I have produced some astro shots with the 25mm f4 DA that I am happy with (though noise is still an issue at the ISOs that are required with an f4 lens). Perhaps there is sample variation and I happen to have a good one...?

Anyhow, if they could pull it off - and do it well - I'd be delighted.
I agree. I will be very happy if Pentax can surprise us, but I don't have a high hope on this.

In my experience, sample variation in lenses usually show up as asymmetry in stellar images, either stars that are not round in the frame center or the four corners show different shapes of stars. I have (or have seen) many Pentax lenses showing such, so my confidence level on the production accuracy of Pentax is quite low. However, on this 25mm/F4 (and my newer 645 lenses), I do not see such symptoms. So there is a good reason to believe it performs close to its design spec. The picture I showed originally have even worse stars in the corners. I did some Photoshop tricks to shrink the stars in the corners so the picture does not look as annoying as it originally was.

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