Frank_BR

Frank_BR

Lives in Brazil Campinas/SP, Brazil
Works as a Engineer
Joined on Jan 20, 2005

Comments

Total: 263, showing: 1 – 20
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In reply to:

Frank_BR: "The focusing mechanism is slow at first, but starts to break-in and become easier to turn with use."

A lens that needs break-in? Hmmm... This points to a lack of mechanical precision and/or lousy quality control.

I have manual focus lenses with over thirty years of use that were always smooth from day one. The Takumars, Nikkors, Rokkors, Zuikos and other lenses from the golden age of manual focus never needed break-in. The helicoids of these lenses were machined with so high precision that a thin film of the grease prevents any metal-to-metal contact. And, if there is no metal-to--metal contact, there is no possibility, nor need of break-in.

A manual focus lens with precision helicoids and, most important, properly lubricated, does not suffer any mechanical wear. It is eternal, mechanically speaking.

Forty years ago, if you said to a buyer of a Super Takumar or a Nikkor lens that the lens needed break-in before use, he would surely laugh.

Direct link | Posted on May 6, 2015 at 17:36 UTC

"The focusing mechanism is slow at first, but starts to break-in and become easier to turn with use."

A lens that needs break-in? Hmmm... This points to a lack of mechanical precision and/or lousy quality control.

Direct link | Posted on May 5, 2015 at 21:36 UTC as 39th comment | 4 replies
In reply to:

Stitzer23: Why do the spots appear at certain f stops only? Its on the sensor after all. Appreciate any explanation please. Thanks.

You're welcome!
Besides the lens aperture, another important factor for the visibility of the spots is the distance from these spots to the sensor, which is basically given by the thickness of the filter stack. The m43 cameras with filter stack of 4 mm are the less prone to show the spots on the sensor, while the digital Leicas with filter stack of only 1 mm are the most. The cameras from Nikon, Canon, Sony, Fuji, Pentax, etc, with filter stack of 2 mm are between these two extremes.

Direct link | Posted on May 3, 2015 at 01:31 UTC
In reply to:

Stitzer23: Why do the spots appear at certain f stops only? Its on the sensor after all. Appreciate any explanation please. Thanks.

In fact, the visibility of spots is given not by the depth of field, but by the size of the umbra (darkest zone of the shadow) produced by blocking the light rays by the spots on the sensor. The size of the umbra depends on the size of the illuminating source, as shown in this figure:

http://www.mcglaun.com/UMBRA.jpg

In the case of a sensor in a camera, the illuminating source is the lens exit pupil, whose size is inversely proportional to the F-number. This explains why the spots on the sensor are more visible for small apertures (F11, F16, F22, etc.)

Direct link | Posted on May 2, 2015 at 16:14 UTC

A positive point of Lomo lenses is that when someone buys a Lomo lens, he need not worry about whether it is within specifications or he got a bad sample. In practice, it is all the same.

Direct link | Posted on May 2, 2015 at 00:32 UTC as 19th comment | 4 replies
In reply to:

Frank_BR: Possibly the spots are micro bubbles of gas that formed after the cameras have gone through quality control.

Or maybe it's a new type of measles that only infects digital sensors :)

Direct link | Posted on May 1, 2015 at 14:31 UTC

Possibly the spots are micro bubbles of gas that formed after the cameras have gone through quality control.

Direct link | Posted on May 1, 2015 at 14:12 UTC as 61st comment | 2 replies
On Massive $33,500 2450mm f/8 NASA lens surfaces on eBay article (235 comments in total)
In reply to:

Frank_BR: This Jurassic lens comes from the film era, when anything less than 6x6 was considered small format. Then digital photography came along...

More than five years ago, Michael Reichmann from Luminous Landscape showed that a digital camera Canon 1DS with "only" 11 MP produced a more detailed image with less noise than a 6x7 film. Today, that the digital sensors are even better than in 2009, a good m43 camera can equal or exceeds the 6x7 film format.

The m43 sensor has a crop factor of about 4x in relation to 6x7, so a modern 600mm lens adapted to a m43 camera should overcome the NASA monster of 2540mm. Besides, if you consider that a CMOS sensor has sensitivity 50 ~ 100 times higher than a 6x7 film, then it's clear why NASA discarded this monstrous lens long time ago.

Unfortunately, Ken Rockwell is not a reliable source. Maybe you should take a look at the Luminous Landscape article I quoted before but forgot to provide the link:

https://luminous-landscape.com/shootout/

Direct link | Posted on Apr 30, 2015 at 01:35 UTC
On Massive $33,500 2450mm f/8 NASA lens surfaces on eBay article (235 comments in total)

This Jurassic lens comes from the film era, when anything less than 6x6 was considered small format. Then digital photography came along...

More than five years ago, Michael Reichmann from Luminous Landscape showed that a digital camera Canon 1DS with "only" 11 MP produced a more detailed image with less noise than a 6x7 film. Today, that the digital sensors are even better than in 2009, a good m43 camera can equal or exceeds the 6x7 film format.

The m43 sensor has a crop factor of about 4x in relation to 6x7, so a modern 600mm lens adapted to a m43 camera should overcome the NASA monster of 2540mm. Besides, if you consider that a CMOS sensor has sensitivity 50 ~ 100 times higher than a 6x7 film, then it's clear why NASA discarded this monstrous lens long time ago.

Direct link | Posted on Apr 29, 2015 at 23:43 UTC as 17th comment | 6 replies
On Massive $33,500 2450mm f/8 NASA lens surfaces on eBay article (235 comments in total)
In reply to:

Frank_BR: Besides getting $33,500 poorer, the owner of this lens will need a new and strong shelf to expose the beast in his living room. Use as a practical photographic tool? None.

It's not just me, sir. NASA also did not find use for this lens after digital photography arrived.

Direct link | Posted on Apr 29, 2015 at 22:28 UTC
On Massive $33,500 2450mm f/8 NASA lens surfaces on eBay article (235 comments in total)

Besides getting $33,500 poorer, the owner of this lens will need a new and strong shelf to expose the beast in his living room. Use as a practical photographic tool? None.

Direct link | Posted on Apr 29, 2015 at 20:39 UTC as 22nd comment | 3 replies

Some thoughts on the Columbia University camera:

1) This is truly a camera for available light photography… provided you are on the beach and never use smaller apertures than F2.

2) The ideal is to use only lenses with apertures greater or equal than F1.

3) Not recommended for astrophotography.

4) If you are fan of the 10-stop ND filters, forget it. But maybe you can use a 0.01-stop ND filter.

5) With a self-powered flash, this camera would be even more versatile.

Direct link | Posted on Apr 17, 2015 at 19:20 UTC as 6th comment
On Opinion: Why the Canon XC10 is a big deal article (810 comments in total)

More than twenty years ago, in the days of, heaven forbid, video 8, Canon had a line of consumer camcorders with rotating grip. That type of grip never caught on. To err is human, to insist on the error is ... Canon.

Direct link | Posted on Apr 9, 2015 at 14:23 UTC as 94th comment

These superzoom cameras are especially interesting for macro and super-telephoto photography. The current 1/2.3" sensors are very good, and certainly better than the sensor used in an iPhone 6, for example. The quality of the pictures produced by a 1/2.3" sensor is not spectacular like a digital FF camera, but it rivals the best 35 mm photographic films from 20 years ago. I think the superzoom cameras are unfairly undervalued.

Direct link | Posted on Mar 2, 2015 at 22:24 UTC as 21st comment
In reply to:

Rich1939: 2000 mm will sell the hell out of this and the resultant atmosphere distorted images will disappoint the hell out of the buyers.

2000 mm can be very useful for shooting birds and small animals at short and medium distances, for which the effect of the atmosphere is negligible.

Direct link | Posted on Mar 2, 2015 at 22:04 UTC
In reply to:

AlexisH: Interesting approach. Hydrophilic rather than hydrophobic.

The filter is hydrophilic because most lenses are hydrophobic. :-)

Direct link | Posted on Feb 26, 2015 at 21:47 UTC
In reply to:

Frank_BR: Wouldn't a deep plastic hood be simpler, cheaper, more effective?

Yes, it applies if the hood is made large enough and the lens is not an ultra wide-angle.

Protecting ultra wide-angle and fisheye lenses from raindrops is an almost insoluble problem. By the way, the "Tokina solution" would probably produce vignetting with these types of lens. Besides, surely you know that the wide angle lenses are especially efficient to reveal specks of dust, dirt, scratches, etc. on the surface of the front lens or filter. Because the raindrops falling on the Tokina hydrophilic filter do not spread immediately for physical reasons, I expect that raindrops will be visible if the lens is under constant rain.

Direct link | Posted on Feb 26, 2015 at 21:34 UTC

Wouldn't a deep plastic hood be simpler, cheaper, more effective?

Direct link | Posted on Feb 26, 2015 at 20:50 UTC as 13th comment | 5 replies
On 45 24mm-Rishi-03-F2.8 photo in dpreview review samples's photo gallery (3 comments in total)

Yes, there is some coma but of low intensity, what makes this lens a good candidate for astrophotography.

Direct link | Posted on Feb 25, 2015 at 21:29 UTC as 2nd comment
On 25 Dan_2282_15mm_f5.6 photo in dpreview review samples's photo gallery (1 comment in total)

Stunning image quality. The ultra wide-angle zoom lenses definitely caught up with fixed focal length lenses.

Direct link | Posted on Feb 25, 2015 at 21:04 UTC as 1st comment
Total: 263, showing: 1 – 20
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