Joel Halbert

Lives in United States Tucson, AZ, United States
Works as a Engineer
Joined on Jul 4, 2003

Comments

Total: 69, showing: 1 – 20
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In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

steelhead3: You are getting into semantics quite literally :) Electro-mechanical is a super-set including (and dominated by) electro-magnetic design (motors of all kinds, solenoids, relays etc.) so almost a synonym. There are non-magnetic actuators such as piezo-electric, and on the receiving side, various capacitive and resistive microphones and accelerometers etc.

The electromagnetic force is fundamental and applies to everything we are talking about. So Copal or others may correctly describe a shutter mechanism as "electromagnetic but calling it "electro-mechanical" is still correct also
I think you'd find that 1/4000 shutters and /8000-capable shutters are both implemented as electro-mechanical designs ( or electromagnetic if you prefer). .

I did see in the search, that some Canon cameras with 1/8000 speed also feature a "soft-touch electromagnetic shutter release button" instead of a conventional switch. Could that be part of what you are referring to?

Link | Posted on May 22, 2017 at 19:07 UTC
In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

Txoni, in this context, electron or hole drift is not the limit of the signal transmission rate, and the length of conductors within the camera is not a practical limit (though good transmission-line techniques will help maintain the cleanliness and fidelity of the signals). The capacitance of the photo-wells is, as I mentioned in earlier comments.

Link | Posted on May 22, 2017 at 17:46 UTC
In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

(...continued)

At some level, the thing must be electro-mechanical because the shutter button itself is not a mechanical trip mechanism, and also the electronic exposure sequence must be synchronized with the curtains. So for many reasons, all-mechanical just cannot be the case.

The issue of fastest speed: this is a combination of the shutter curtain travel rate and the minimum slit-width, i.e. how closely the 2nd curtain can follow the 1st. To achieve 1/8000 etc. without a hard-to-control, very narrow slit width, you may need a faster curtain which is more expensive to achieve with constant rate across the image plane (and requires more extensive shock-absorption to keep down noise and blur-inducing vibration). That is probably why cheaper cameras have slower top speeds (could also have a market-differentiation strategy component). Again, I think electro-mechanical is the only practical and cost-effective concept.

This side discussion, of course, does not belong in the article.

Link | Posted on May 22, 2017 at 17:37 UTC
In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

steelhead3: Well, I did a quick search on the 6d for "mechanical shutter", and what I found was a discussion of electronic or "silent" shutters and electronic first-curtain modes. So in that context, "mechanical" shutter is a reference to the physical shutter curtains. It does not necessarily mean, and I doubt it does, that those mechanical curtains are mechanically timed. Today it's hard for me to imagine that a clockwork timer is cheaper than an electronic timer. Making this even more unlikely is that without a wind lever, you'd need motor power just to wind the clockwork. Some shutters now use linear motors or glorified solenoids. Also, these complex partially-electronic exposure modes would be hard to integrate with a clockwork shutter. Therefore at some level I believe that all of these cameras have an electro-mechanical shutter mechanism, even though the word "mechanical" may appear in discussions to contrast with sensor-based "shutter" modes.

(continued...)

Link | Posted on May 22, 2017 at 17:34 UTC
In reply to:

Alex Permit: "Smaller sensors also have an advantage in this respect: less physical distance to travel means rows can be read-out quicker"

How does the PHYSICAL distance effect the electronic read speed of a sensor? Electromagnetic waves travel at one foot per nanosecond, so it can't be how long it takes the electrons to move.

noirdesir, see my comments just after this (i.e. just above in my comment-page layout). There are fundamentals (though not physical distance across the sensor) that challenge the readout rate of high-pixel count with large pixels. True that engineering fast readout generates more heat, but for low duty-cycle still photography application, I don't think that is the primary issue. It becomes more so in video which is constantly reading out and re-setting.

Link | Posted on May 22, 2017 at 16:56 UTC
In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

Kharan:
Right, I was responding to the text "less physical distance to travel means rows can be read-out quicker", which refers to an all-electronic process, so it shouldn't relate to the physical curtains. I'm saying the readout rate is challenged by a) the number of pixels (rows x columns) but also by b) the photo-well capacity -> electrical capacitance, and not incidentally by the requirement to maintain low noise. The same characteristics that give FF sensors higher dynamic range makes them harder to read out very fast.

Link | Posted on May 22, 2017 at 16:50 UTC
In reply to:

Joel Halbert: Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

steelhead3: True that an overlapping-rigid-blade shutter can be mechanically timed, but I don't think that's very popular anymore. All-mechanical shutters had a certain "pro" appeal in film cameras that could function with a completely dead battery, but this is of little note in a digital camera where battery power is essential. So yes, in my suggestion you could drop the "electro-mechanical" modifier, but I'd leave it in as the "most popular" or "most common" type. Mostly, I was concerned that a newcomer might read the article and come away thinking that "focal-plane shutters work just like this" which is not the case.

Link | Posted on May 22, 2017 at 16:49 UTC

Richard, nice article. A few minor points:

1. Noted by others: "focal plain" and "focal plan" obviously should read "focal plane".

2. Your description implies that focal-plane shutters all use metal multi-blade, vertically-traveling curtains. Popular today, but originally they were roll-up blinds on cylinders, like a window shade. Some of the earliest ones were vertical, then for decades most 35mm cameras used Leica-style, horizontally-traveling rubberized-cloth or foil shutter curtains (Zeiss Contax used a vertical metal "tambour door" style roller-shade). Perhaps you should simply insert
"We'll discuss today's most popular design of electro-mechanical focal-plane shutters:"
right before the sentence
"At the start of the exposure a series of horizontal blades..."

3. Readout speed of FF sensors is not slower due to physical distance; electrons travel very fast. But each pixel is bigger & holds more charge; therefore has higher capacitance and is slower to read with low added noise.

Link | Posted on May 22, 2017 at 16:13 UTC as 26th comment | 13 replies

When Best-Ever Gadget Company runs a contest or sweepstakes to create excitement around their products, the rules will read as

"Entry not open to individuals or family members employed by Best-Ever or its subsidiaries, advertising partners, consultants or contractors" etc.

This is in addition and in spite of to all efforts to keep the judging and/or prize drawings completely above-board. It simply defeats the purpose of the contest to have suspicion and bad publicity cloud the outcome, and in the case of a skills competition, it ruins the inclusiveness aspect that draws enthusiastic participants.

In other words, this incident illustrates the soundness of some very old and well-established principles, and the dangers of trying to ignore them.

Link | Posted on May 2, 2017 at 16:36 UTC as 38th comment
In reply to:

Peerg: Great lens. I have the panasonic 7-14. And that sense does not work well on olympus bodies under some circumstances, and give purple blobs. Will this 8-18 lens fix that problem? I love the 7-14 light and good performances. The oly 7-14 is good too, but to big!

It seems that the core issue is that Panasonic lenses (coatings) do not block UV spectrum because that is taken care of in the sensor stack. Olympus is the opposite; the lenses do not pass near-UV but the sensor records it. Therefore the "purple blob" issue, in flare-prone shots, needs to be addressed with an add-on filter when using Panasonic lenses on Olympus bodies. One of the lesser but still troublesome interoperability concerns in the MFT system.

The Lumix 7-14 has no filter thread or slot, but some people have rigged solutions to add one.

The fact that you can screw on a UV-blocking filter is a reason to believe that the 8-18 can do better than the Lumix 7-14 on Olympus bodies. You should buy a top-quality filter, with excellent coating, to minimize additional reflections with the wide-angle lens.

Link | Posted on Apr 19, 2017 at 16:27 UTC
On article Archos to make Kodak-branded Android tablets (142 comments in total)
In reply to:

Stacey_K: What is sad, Kodak used to manufacture world class optics in the US back in the first half of the 20th century, as well as their film products. They actually made some good CCD sensors at the start of the digital revolution. Then at some point a few CEO's types wanted to become super rich milking the company dry, thousands of people lost their jobs so these few could afford a bigger yacht. And now they are trying to milk the last dime out of the brand name.

What happened to Kodak is not simply about financial types milking the assets (Sears would be a sad example of that). Kodak wanted to stay in business as a growing and innovating concern; they just completely underestimated the pace of the digital-camera market takeover (despite essentially inventing the technology and trying to participate), the rate of plummeting film sales, and the almost-complete switch-over from paper photos to electronic PC and phone display & sharing. Film was so profitable, and disappeared so fast, that the company couldn't and didn't anticipate the pace of needed re-structuring. Any of us, even armed with the exact history of what happened, would be hard-pressed to go back to 1995 and shepherd the healthy re-shaping of Kodak into a different huge company, based on a vastly different technology and a completely different consumption model.

Link | Posted on Feb 17, 2017 at 06:38 UTC
On article Archos to make Kodak-branded Android tablets (142 comments in total)
In reply to:

OlyPent: They aren't the only ones who have fallen. Look at the crap Vivitar is making/rebranding:
http://www.abcactionnews.com/news/region-east-hillsborough/plant-city/exclusive-ear-phones-exploded-in-plant-city-mothers-ear-while-she-was-wearing-them

BlueBomberTurbo is correct. Vivitar (originally Ponder & Best) was always an importer and seller of re-branded and own-brand (custom contract-designed) photo equipment, usually running somewhere from decent to very good performance and quality.

Vivitar has since been sold a few times (?) but it's not really a "fallen" and now-licensed brand like Kodak and Polaroid. Those were among the legion of American designer/manufacturers whose famous but nearly-defunct brand name became a bankruptcy-court asset. Vivitar had some fine and famous products but they were always designed and manufactured under contract or simply re-branded. The current Vivitar may be more of the latter.

Link | Posted on Feb 17, 2017 at 06:18 UTC
In reply to:

samfan: It looks absolutely beautiful but horrendously impractical to use.

Also, single exposures? That's pretty silly even for this concept. Of course, the most amazing cameras technology-wise tended to be pretty crazy.

As with many cameras of that era, sheet film was one option. There was also a rollfilm back that took spools of Compass film (not standard 35mm cassettes which were too big to go with the camera).

Link | Posted on Jan 31, 2017 at 15:52 UTC

How's this for the ultimate firmware upgrade policy - the original Compass I model was superseded by an improved Model II design, not long into the product life cycle. if you purchased a Compass I camera, you were entitled to have it completely replaced by the improved Model II.

Link | Posted on Jan 31, 2017 at 15:51 UTC as 31st comment | 1 reply
In reply to:

Michel Cojan: Nice, but it looks more like stainless steel (thus the heaviness...), not aluminium. Swiss made. And yes, it would be nice if this would "inspire" some today's camera makers for some mini FF or APS-C digital models.

It is in fact aluminum; most Compass cameras have a slightly dull aluminum patina from handling and air exposure over the years. The reason it's heavy for the size is that it is not an aluminum shell, but a block (or billet) of aluminum that is machined out to make the camera body.

Link | Posted on Jan 31, 2017 at 15:48 UTC
On article Leica M10 real-world sample gallery (345 comments in total)
In reply to:

RetiredDilettante: I found them no better than my 1952 Browning! I was really looking forward to getting this camera. But these images leave me cold! Aurora? NOTHING about them gave me a sense of "Aurora" IMHO. What happened Leica? Disappointed...

RD,

First, a 1952 Browning would be a rifle or a pistol. Perhaps you mean a 1952 Brownie, which would be a Kodak camera.

Second, if you were really "really looking forward to getting this camera" you might not want to let a batch of DPR samples put you off so easily. Take your time and wait for more before you decide.

Third, as Mustafa said, you might mean "aura" not Aurora. People have discussed the Leica "glow" but no one claims it to be the source of the Northern Lights. And said glow, if achieved, is really a function of the lenses and not the M body itself.

If I were you, I wouldn't infer any radical superiority, nor radical inferiority, of the M10's CMOS imager compared to other FF picture-taking boxes. If you buy it to take pictures, you do so because of the way it operates, the way you would use it and the fact that it is a platform for the lenses.

Link | Posted on Jan 22, 2017 at 18:54 UTC
On article Leica Boss: Hands-on with new Leica M10 (169 comments in total)
In reply to:

Painting with light: I like what I see. The only thing I am really missing is an autofocus. I own a fuji xt2 and a Leica Q. Both are wonderful cameras. The Leica Q is very responsive, the image quality is outstanding, and it is working with a very fast autofocus. The only limitation is the 28 mm lens. It may not be possible for Leica to build a full frame camera this size with exchangeable lenses. If so, I would prefer another Leica Q with a 50 mm lens instead of the Leica M 10.

Point of history - the Leica model II (aka Leica D in the USA) was the first model with built-in coupled rangefinder, and was advertised as "The Autofocal Leica" - and it was, in the day. I don't have a ready link for that ad, but here's a related one advertising a Leica III-series model with the "Automatic Focusing":
http://camerasinthemedia.tumblr.com/post/75027859980/fromand-vintage-leica-ad-automatic-focusing

Link | Posted on Jan 19, 2017 at 06:53 UTC
On article Leica Boss: Hands-on with new Leica M10 (169 comments in total)
In reply to:

AbrasiveReducer: Looks nice. Since this is for traditionists, I wonder, would it be too much to ask for that lovely Leica script engraved on that blank top plate? And you can lose the red dot, which is like a guy driving a BMW with a license plate frame that says "BMW."

I'd say it's more like a guy driving a BMW with a BMW grille attached to the front. In other words. a brand-identifying design feature.

Very much like Canon L lenses with red rings., or premium Nikkors with gold rings.

For some reason the Leica red dot logo, which I find not at all objectionable, has been beaten to death as some kind of ever-amusing joke. The joke itself is now a tiresome echo, a predictable snicker in every DPR Leica press-release comment section.

There are Leica exclusivity-appeal practices that I don't particularly like, but the simple and red-dot logo isn't one of them.

Link | Posted on Jan 19, 2017 at 06:28 UTC
In reply to:

dmanthree: Further proof that this wasn't really designed for still shooters. Yes, the new sensor and IS are good, but every review or summary I've seen of this camera focuses on the *very* video-centric features. I'll be acquiring an Oly EM1 II when they're available.

I see this comment quite often, usually to justify Olympus vs. Panasonic. However, it's not clear how the rich video capabilities actually hurt the still-shooting capabilities. If you could explain I'd appreciate it. And since EM1 MkII now has 4k recording and other improved video features, would you say that it too has taken a hit as a desirable still camera?

Link | Posted on Jan 17, 2017 at 04:41 UTC
On article Panasonic Lumix DC-GH5 Review (1185 comments in total)
In reply to:

mpgxsvcd: I thought the GH4 had auto ISO in manual mode? Does the GH5 have Auto ISO in manual mode plus exposure compensation?

Yes, I think this is one of the most significant points about this camera. Easy to overlook when people complain about sensor size.

Link | Posted on Jan 4, 2017 at 21:51 UTC
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