Peter Cockerell

Joined on Mar 7, 2012

Comments

Total: 28, showing: 1 – 20
« First‹ Previous12Next ›Last »
In reply to:

Zdman: You forgot the main advantage which is lens design. To achieve the same depth of field and light gathering you can design a lens one stop higher than you would for full frame. So instead of making design trade offs with a F2 design you can go to F2.8 with less spherical aberration and chromatic abberations etc. Go to large format and you can design crazy good F5.6 lenses and still get the depth of field of a full frame at f1.4. Why do you think large format hasn't got lenses much faster than F5.6? Because they don't need it (the DOF would be too small) and the results at F5,6 are spectacular. Its not just about the silicon its the lenses. Extrapolate the MF F2.8 (which would probably only need 6 elements) and light gathering to M43 and you'd need an F1 lens which is just not feasible to design.

" Go to large format and you can design crazy good F5.6 lenses and still get the depth of field of a full frame at f1.4."

Only if the "large" format camera had a crop factor of 0.25x and a sensor area 16 times that of a full-time camera. Which model is that, and how much does it cost?

Link | Posted on Mar 23, 2017 at 17:02 UTC
In reply to:

Greg Gebhardt: Kinda shows how China is getting way ahead of us. All the wonders in the world are no longer here.

Only the most parochial-minded of Westerners would ever have believed all the wonders of the world were "here".

Link | Posted on Feb 25, 2017 at 17:34 UTC
On article Sigma Announces 100-400mm F5-6.3 DG OS HSM lens (154 comments in total)
In reply to:

janist74: Sigma is very clever.

They address the "size disadvantage" of FF/APS-C cameras (instead of Canon/Nikon). This lens is barely bigger than the Pana 100-400 MFT lens ( a tad slower and heavier though). If the IQ is good enough for an APS-C 24mP camera, then it will sell very good.

ps.: my only reservation: if the Pana 100-400mm has quite strong vignetting with a filter thread of 72mm then what this lens can do with 67mm...

Yep! ! was using 1.5-1.6 as the APS-C:MFT factor instead of the correct (2 over that number), i.e. 1.25-1.33, so my MPixel counts for APS-C should have been 20-21.3M pixel. So as you say, current APS-C sensors do have a slight pixel density advantage over older MFT ones, but not, I think, over a 20.3M pixel GH-5

Link | Posted on Feb 22, 2017 at 02:26 UTC
On article Sigma Announces 100-400mm F5-6.3 DG OS HSM lens (154 comments in total)
In reply to:

janist74: Sigma is very clever.

They address the "size disadvantage" of FF/APS-C cameras (instead of Canon/Nikon). This lens is barely bigger than the Pana 100-400 MFT lens ( a tad slower and heavier though). If the IQ is good enough for an APS-C 24mP camera, then it will sell very good.

ps.: my only reservation: if the Pana 100-400mm has quite strong vignetting with a filter thread of 72mm then what this lens can do with 67mm...

+NetMage No, because to confer the kind of digital zoom advantage that you imply, the larger sensor camera would need a greater pixel density, not just greater pixel count. Even for a trailing-edge 16M pixel MFT sensor, an APS-C sensor would need to exceed 36-41M pixels and a full-frame would need to exceed 64M pixels. I don't know of any available cameras that meet those requirements (and of course the numbers are even greater for a newer 20M pixel MFT sensor).

Link | Posted on Feb 21, 2017 at 15:47 UTC
In reply to:

Jefftan: These adapter won't work with EF-S lens as far as I know
They are for full frame EF lens

any EF-S to E adapter for Sony APS-C camera

Thanks

Though of course you wouldn't want to use a speed booster adapter with an ef-s lens on an aps-c body, or you'll get severe vignetting.

Link | Posted on Jan 25, 2017 at 18:36 UTC
In reply to:

Paul_B Midlands UK: Clearly Nikons in the light not sound business. This video is a lot more enjoyable with sound on mute. Some great and poerrful imagery, Nikon is a global brand everyone knows the name. I've never owned one yet.

Absolutely. The voice-over, music and lyrics were all execrable. OK visuals, though.

Link | Posted on Jan 11, 2017 at 09:59 UTC
In reply to:

Peter Cockerell: What assurance is there that these Chinese-manufactured phones aren't sending your Google contacts and captured passwords to a site in China?

I was thinking of this story specifically, for those who haven't seen it:

http://mobile.nytimes.com/2016/11/16/us/politics/china-phones-software-security.html

Plus Huawei (manufacturer if the Nexus 6P) routers, of course:

http://www.techeye.net/business/huawei-products-do-have-backdoors

Personally I'd rather take my chances with the NSA than the Chinese equivalent under Xi Jinping.

Link | Posted on Dec 2, 2016 at 03:39 UTC

What assurance is there that these Chinese-manufactured phones aren't sending your Google contacts and captured passwords to a site in China?

Link | Posted on Dec 1, 2016 at 00:38 UTC as 9th comment | 6 replies
In reply to:

Peter Cockerell: For the 65mm "macro", where are they measuring the minimum focus distance from? If it's the focal plane, as is usual, then the magnification will be 0.43 (1:2.3), far short of a true 1:1 macro. That's actually the best case. If they're measuring it from, say an effective lens plane about halfway through the lens, the magnification will be around close to 0.31 (1:3.2). To be a true macro lens, the minimum focal distance would need to be 0.26m or less (4x the focal length). I always thought that if a lens mentioned "macro" in its name, then it's a true macro lens.

+Henning W, thanks for the clarification. The only macro lens I've owned is a Tamron which is specifically 1:1.

Link | Posted on Oct 10, 2016 at 16:14 UTC

For the 65mm "macro", where are they measuring the minimum focus distance from? If it's the focal plane, as is usual, then the magnification will be 0.43 (1:2.3), far short of a true 1:1 macro. That's actually the best case. If they're measuring it from, say an effective lens plane about halfway through the lens, the magnification will be around close to 0.31 (1:3.2). To be a true macro lens, the minimum focal distance would need to be 0.26m or less (4x the focal length). I always thought that if a lens mentioned "macro" in its name, then it's a true macro lens.

Link | Posted on Oct 6, 2016 at 18:36 UTC as 5th comment | 3 replies
On article Throwback Thursday: Canon PowerShot Pro70 (111 comments in total)
In reply to:

trenzterra: As a Singaporean, I found the photos pretty familiar, then I realised: cool! The sample photos were taken in Singapore.

Was Phil based in Singapore back then?

Interesting, I guess just because a camera produces subjectively appealing shots, that doesn't mean the colors are necessarily accurate!

Link | Posted on Sep 17, 2016 at 02:02 UTC
On article Throwback Thursday: Canon PowerShot Pro70 (111 comments in total)
In reply to:

trenzterra: As a Singaporean, I found the photos pretty familiar, then I realised: cool! The sample photos were taken in Singapore.

Was Phil based in Singapore back then?

Yes, Phil lived in Singapore for several years at the start of dpreview. The sample photos often featured his lovely Singaporean wife, but Phil was never shown. I think I only ever saw one photo of him, where his face was obscured by the camera he was holding!

I still remember his review of the Pro70, which I definitely coveted at the time. Even then, though, the resolution was lower than the cheaper competition (I ended up getting a Casio!) But there's no denying how nice the colors are, and I often wonder why Canon didn't persevere with that alternative to the Bayer mask.

Link | Posted on Sep 16, 2016 at 03:34 UTC
In reply to:

piratejabez: The full PDF has some great examples: http://arxiv.org/pdf/1608.05148v1.pdf
I'm going to extract the images from it for better comparison :)

I wonder what compression was used for the images in the PDF. Lossless, hopefully...

Link | Posted on Aug 25, 2016 at 01:28 UTC
On article Bentley creates a 53 billion pixel car commercial (189 comments in total)

My god, what an utter load of billocks. How does dpreview fall for this kind of crap?

Link | Posted on Jul 21, 2016 at 22:31 UTC as 27th comment
In reply to:

The Squire: Did someone in Sony marketing do that math?

"So 12 cameras, each shooting 4k... that must mean it's a 48K video! WOW! Press release... done!"

Doesn't account for the need to significantly overlap the output from each individual camera.

If there was *no* over lap, then shooting those cameras in portrait and stitching together gives a theoretical output width of 12x2160px = 25.920px... aka 26K?

When pedants and marketing collide...

But this one goes to 11...

Link | Posted on Jan 13, 2016 at 14:57 UTC
In reply to:

tesch: I don't come to this website very often but when I do I find all of the talk is about why Sony isn't a real camera. Very strange!

This is a good article about a lot of things that really have no effect on the images taken by people on this site. If the photographers on this site spent as much time researching composition and color theory they wouldn't have to worry about this nonsense. But that would mean they would have to think which seems to be an issue..........

Get over it!

@HowaboutRAW A better comparison would have been with a composer thinking about music theory when he's composing. Which I imagine he does.

But the issue isn't as moot as tesch seems to think. That "moon and Space Needle" shot doesn't seem like an especially tricky exposure, but it's way too artifacty (which is a word, I've decided) to rank as stock-ready.

Link | Posted on Sep 4, 2015 at 19:01 UTC
In reply to:

Frank_BR: Why doesn't Sony have so far the option of a lossless RAW format? Most critics say that this is just a Sony error, but the question is not so simple. To try to understand better, I did an experiment. I took the RAW files from DPR Studio Scene for Sony 7RII and Nikon D810, and compressed them with WinRAR. The results were as follows:

Camera.....RAW original....WinRAR compr
7RII .........41.4MB...........38.3MB
D810 ........74.3MB..........43.9MB

WinRAR is a lossless compression, so the RARs files contain the same information as the RAWs from camera.

Surprisingly, WinRAR managed to reduce to almost half the size of NEF file, but failed to appreciably reduce the size of Sony RAW. This shows that NEF is inefficient since it produces much larger files than necessary. There is room for a better lossless RAW coding. I draw the conclusion that a reason for Sony has been reluctant to use a lossless RAW coding is that the current processor technology does not allow high efficiency of coding.

I think all Frank is saying is that NEF is quite inefficient if a general-purpose lossless compression algorithm can reduce the size by a third. Since Nikon has a much better knowledge of the data stream than RAR does, it should be able to do even better than RAR. I assume the redundancy comes from keeping data aligned on byte or word boundaries for faster processing (e.g. they might store a 12-bit sample in two bytes, wasting 4 bits per sample, rather than storing two samples in three bytes without waste.

I agree, though, that the main question is why does Sony think it's acceptable to apply lossy compression to their RAW format, especially when it can lead to such ugly artifacts.

Link | Posted on Sep 4, 2015 at 18:47 UTC
On article Phase One 645DF+ with IQ250 field test (136 comments in total)
In reply to:

Peter Cockerell: I'm a bit confused by use of 5/6 as the lens equivalence ratio between the IQ250 sensor and a 35mm one. Of course, it's tricky to come up with a single number when the aspect ratios of the sensors are different, but in this case the relevant numbers are: horizontal: 36/44 = 0.82 (or 9/11 if you prefer fractions), vertical: 24/33 = 0.73 (or 8/11), diagonal: 43.3/55 = 0.79 (or about 393/500, or 8.7/11). Concentrating on the diagonal, since that's what you mention in the article, the fraction is much closer to 4/5 than 5/6, and the focal length equivalents would be: 120mm becomes 94mm, 80mm becomes 63mm, and 45mm becomes 35mm.

True enough. I guess it all comes down how important those incremental differences are to the person taking the photos. I had to make a similar decision last year when I moved from a 5D3 to a GH4, because I was just getting fed up with lugging a around a full-frame and all its associated lenses. For my (purely personal) photography. I'd say for 80% of the photos I take (which are mostly for web display), the loss of resolution and noise performance hasn't made any difference to the end results, but for the other 20% I sorely miss the benefits of the full-frame. Which is why I'm seriously considering buting an A7R II to use with the lenses I couldn't bear to part with (Canon EF 70-200 L II and a couple of Sigma primes).

Link | Posted on Jul 10, 2015 at 20:10 UTC
On article Phase One 645DF+ with IQ250 field test (136 comments in total)
In reply to:

Peter Cockerell: I'm a bit confused by use of 5/6 as the lens equivalence ratio between the IQ250 sensor and a 35mm one. Of course, it's tricky to come up with a single number when the aspect ratios of the sensors are different, but in this case the relevant numbers are: horizontal: 36/44 = 0.82 (or 9/11 if you prefer fractions), vertical: 24/33 = 0.73 (or 8/11), diagonal: 43.3/55 = 0.79 (or about 393/500, or 8.7/11). Concentrating on the diagonal, since that's what you mention in the article, the fraction is much closer to 4/5 than 5/6, and the focal length equivalents would be: 120mm becomes 94mm, 80mm becomes 63mm, and 45mm becomes 35mm.

Thanks for the confirmation, JNR and Androole. Another thing that occurs to me is how close the ratio is to 1. How much of a real-world advantage would a small "medium format" back like this have over, say, an EOS 5DS or a Sony A7R II? Especially when you consider all the other compromises inherent in this model. (Though it's true that the sensor size ratio is more significant if you constrain your 35mm camera to a 4:3 aspect ratio, I guess.)

Link | Posted on Jul 10, 2015 at 16:39 UTC
Total: 28, showing: 1 – 20
« First‹ Previous12Next ›Last »