Amin Sabet

Amin Sabet

Lives in United States Boston, United States
Joined on Sep 3, 2004

Comments

Total: 26, showing: 1 – 20
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On What is equivalence and why should I care? article (1742 comments in total)
In reply to:

Amin Sabet: Relationships between format size, depth of field, angle of view, focal length, etc, are not new or controversial.

What is referred to here and within the forums as "total light equivalence" is intellectually interesting but of more limited practical value. When you consider the vast array of sensor efficiencies we encounter, from films of various makes and speeds to digital sensors of different generations and designs, assumptions about image quality based on total light gathering will often fail to hold up.

What is underemphasized in this article is that for shooting in relatively limited light where shorter exposure times and non-shallow DOF are desired (applies to most street photography for example), there is no inherent image quality advantage to larger formats. On the contrary, smaller sensors tend to be slightly more efficient.

There is no accepted definition of "photographic equivalence", regardless of what this article or loud voices in the forum echo chamber suggest.

@nerd2 and Jylppy: I'm not missing anything, and I didn't state that smaller sensors are always more efficient or that MFT sensors in particular are more efficient. I stated that smaller sensors tend to be more efficient. At least in my experience with tons of small and big sensors over the years.

This has been discussed in great detail in many threads. Here are a couple:

http://www.dpreview.com/forums/post/52448388

http://www.dpreview.com/forums/post/53180486

The pixel density issue is complicated. Here's my take on it:

http://www.dpreview.com/forums/post/50051764

@Joe:

Part 1: We've been here before. I have no need to repeat myself to you.

Part 2: I'm not arguing for a different definition of equivalence than the one you have put forth. I don't accept that it has any established meaning at all.

/End discussion for me. Not enough time in the day.

Direct link | Posted on Jul 9, 2014 at 22:14 UTC
On What is equivalence and why should I care? article (1742 comments in total)

Relationships between format size, depth of field, angle of view, focal length, etc, are not new or controversial.

What is referred to here and within the forums as "total light equivalence" is intellectually interesting but of more limited practical value. When you consider the vast array of sensor efficiencies we encounter, from films of various makes and speeds to digital sensors of different generations and designs, assumptions about image quality based on total light gathering will often fail to hold up.

What is underemphasized in this article is that for shooting in relatively limited light where shorter exposure times and non-shallow DOF are desired (applies to most street photography for example), there is no inherent image quality advantage to larger formats. On the contrary, smaller sensors tend to be slightly more efficient.

There is no accepted definition of "photographic equivalence", regardless of what this article or loud voices in the forum echo chamber suggest.

Direct link | Posted on Jul 9, 2014 at 19:24 UTC as 102nd comment | 12 replies
On Am I missing something here? article (636 comments in total)

"Perhaps I'm inferring a confused message from the company's Nikkor 1 lens line-up: a range of light-sapping consumer grade F3.5-5.6 zooms, a fairly modest 27mm equivalent F2.8, a useful 50mm equiv F1.8 and an 85mm equivalent F1.2. That's just two serious enthusiast-targeted lensed, and one of them costs $900."

I count three serious enthusiast-targeted lenses there, and it's always good to have one pricy one :). Seriously, though: wide, normal, short tele. Definitely have the traditional enthusiast covered there, and it's more than either Canon or Nikon have done for their dedicated APS-C lens lineups.

Direct link | Posted on Mar 16, 2014 at 01:44 UTC as 67th comment | 1 reply
On Canon PowerShot G1 X Mark II: a quick summary article (534 comments in total)

Looks amazing. Sign me up.

Direct link | Posted on Feb 12, 2014 at 16:38 UTC as 90th comment
In reply to:

stevens37y: Either the AA filter or the moire will ruin the fun.

They just need a much higher MP sensor - a high enough resolution sensor will take care of aliasing concerns.

Direct link | Posted on Nov 22, 2013 at 17:09 UTC
On Google working on RAW imaging for Android post (84 comments in total)

It's about time. Way overdue!

Direct link | Posted on Nov 20, 2013 at 03:43 UTC as 28th comment
On Just posted: Sigma 35mm F1.4 DG HSM lens review article (182 comments in total)
In reply to:

itsastickup: Totally hopeless bokeh test.

For me it's a deal-breaker: bad bokeh means unusable portraits.

Closing down the aperture can get rid of hard edged rings but also double-line 'nissen' bokeh which make for poor/disturbing bokeh as in the two pics (I would call this bokeh 'poor' and unusable). Typically I shoot f1.4 lenses at f2 for bokeh reasons. But in addition, you are more likely to get rings where the focus is at a distance and the blur moderate, as with these pics, while at close portrait distances the rings may not be so hard; which is the type of photos I am most interested in.

On top of that: a closed down aperture can be useful (one doesn;t always want obliteration-bokeh) but the bokeh can deteriorate.

So effectively we need a range of apertures and distance to know what the bokeh situation is.

Bokeh is so neglected that I have to do a lot of research to work out whether a lens is any good. It's a pain.

The Sigma has more attractive bokeh than the Nikon and Canon to my eye. Looks better than the Summilux M ASPH FLE to me as well. Here are a couple comparisons to the Canon and Nikon lenses:

http://www.dchome.net/forum.php?mod=viewthread&tid=1161962&extra=&page=1

http://lcap.tistory.com/entry/Sigma-35mm-f14-vs-Canon-35mm-f14-L

Not sure why DPR had "Slightly fussy rendition of out-of-focus backgrounds under some conditions" as a con. That statement apples to all lenses!

Direct link | Posted on Dec 22, 2012 at 22:07 UTC
On Just Posted: Canon PowerShot G15 review article (340 comments in total)

In the 'Features' section there is a great figure comparing equivalent apertures, and I think the data shown for the Panasonic LX7 are based on the whole sensor dimensions (1/1.7" sensor). However, the implementation of that camera's multi-aspect ratio sensor is such that it is effectively 6.7 x 5.1mm (1/1.8") in 4:3 aspect ratio and less than that in other aspect ratios.

Taking that into consideration, the LX7 lens becomes 24-89mm f/7-11.6 equivalent with crop factor calculated based on sensor area or 24-91mm f/7.2-11.8 equivalent with crop factor based on sensor diagonal.

Direct link | Posted on Nov 23, 2012 at 15:37 UTC as 26th comment | 3 replies
On Just Posted: Canon PowerShot G15 review article (340 comments in total)
In reply to:

Amin Sabet: Excellent review. Really well done.

I found one error when comparing the G15 "RAW" conversions to the LX7 using your tool. If you try that comparison at ISO 80 (or any other ISO), you'll see that the LX7 looks much more detailed and noisy. Striking difference compared to the much more "processed" looking G15. However, when opening the downloadable RAW files in Lightroom, they look basically the same.

I find Raw Therapee a lot of work to get the colors and black points, etc, to match up. In the end I want to know how these cameras will work in my workflow, which is Lightroom.

However, if you download the LX7 and G15 RAW files and try them in RAW Therapee, I think you'll find them quite similar, in contrast to what DPR shows in their tool. As well, I have never found that an alpha or beta version of LR 4 is as disparate from the release version as what DPR has shown. I think maybe they uploaded the in-camera JPEG in lieu of the converted RAW for some of those G15 samples. Or something like that.

Direct link | Posted on Nov 23, 2012 at 15:30 UTC
On Just Posted: Canon PowerShot G15 review article (340 comments in total)
In reply to:

Najinsky: Strange, I find in the image test (raw) section, the tests from the silver rated, smaller, lighter RX100, show the RX100 images to be bigger, cleaner and have more detail.

In the 'compact' group, if a camera is more compact and delivers better images, shouldn't it be getting a better award than a bulkier compact delivering lesser images?

I guess controls and ergonomics have to play a part, but taken to extremes, it suggests the question just how poor can the IQ be and still get a gold award?

Not that the IQ here is poor, nor anything wrong with the camera, but for a pocketable camera with big camera IQ, I just couldn't see myself choosing this over the Sony. So I guess what I'm really saying is I'm not sure who your gold award is speaking too. An older generation perhaps, who can't use a rear mount click wheel to change settings?

Maybe the "Gold Award" is speaking to people who:
-Want to spend less than $650
-Want a 5x zoom
-Want better edge/corner sharpness than the Sony can deliver
-Want more tactile controls than the Sony

I have no horse in this race. Bought the Sony RX100, didn't love it, and gave it to my brother. If I were going to buy another camera in this segment - and I don't plan to do so - it would probably be the LX7, X10, or maybe a DP2M.

The point is that all of these cameras have a lot of things going for them, and DPR decided that their target population is best served by rating the G15 higher than the RX100. For someone wanting to take photos at 45mm equivalent on a tripod in good light, a DP2M might get the "Gold" award. As long as you know what's "Gold" for you, you're all set.

Direct link | Posted on Nov 22, 2012 at 12:01 UTC
On Just Posted: Canon PowerShot G15 review article (340 comments in total)

Excellent review. Really well done.

I found one error when comparing the G15 "RAW" conversions to the LX7 using your tool. If you try that comparison at ISO 80 (or any other ISO), you'll see that the LX7 looks much more detailed and noisy. Striking difference compared to the much more "processed" looking G15. However, when opening the downloadable RAW files in Lightroom, they look basically the same.

Direct link | Posted on Nov 22, 2012 at 11:43 UTC as 63rd comment | 2 replies
In reply to:

SunnyFlorida: The Nikkor 35mm F/1.8 sells for $180, the 35mm F/2.0d sells for $270 and can be used in 2 formats, Oly is asking $500 for this???

"But the 35/2 on "FF" would be stopped down to 3.5 for a fair comparison. (Fair= same angle, same DOF, same number of photons captured per time)"

There is no such thing as a "fair competition". Certainly no definition that has anything to do with photons. It's perfectly fair for one person to want a lens that can used without hesitation wide open. It's also fair for another person to want the best possible sharpness for a given DOF and framing. Another person may put a high value on lack of axial CA.

Pricing is about maximizing profit, period. The market will determine whether Oly is charging the right price for this. Same is true for Canon's new $850mm 35mm f/2 lens.

Direct link | Posted on Nov 15, 2012 at 17:02 UTC

I prefer the shape of the 7" Android tabs, which are narrow enough to hold in one hand or slide into my dress pants pocket.

Direct link | Posted on Oct 23, 2012 at 21:34 UTC as 33rd comment
On Just deployed: New dpreview.com forums system article (699 comments in total)

As I mentioned earlier, I like the new system. Just wanted to add that I'm looking forward to a more phone-friendly forum system. I'm sure that is in the works!

Direct link | Posted on Oct 7, 2012 at 13:08 UTC as 62nd comment
On Just deployed: New dpreview.com forums system article (699 comments in total)

I like it. Major improvement.

Direct link | Posted on Oct 3, 2012 at 23:52 UTC as 335th comment
On iPhone 5 vs. iPhone 4S: Image comparison article (94 comments in total)

Apple already stated - same lens, same sensor. Seems like there is a mistake in the EXIF.

Direct link | Posted on Sep 13, 2012 at 22:34 UTC as 18th comment | 1 reply
On Snowy Plover Chick in the Adorable baby animals challenge (10 comments in total)

Super cute :)

Direct link | Posted on Jun 11, 2012 at 01:12 UTC as 6th comment

Impressive!

Direct link | Posted on Jun 11, 2012 at 01:08 UTC as 1st comment
In reply to:

zyran: Let the Battle of the Equivalence begin.

Doesn't Olympus know that you divide the focal length by the f-number, multiply by the weight of the glass in grams, and divide by 20 to get the equivalent price? Someone needs to learn them about Total Light Collection. TLC, baby. This lens is way overpriced.

Direct link | Posted on May 25, 2012 at 06:02 UTC

Pre-order placed. Can't wait!

Direct link | Posted on May 24, 2012 at 22:25 UTC as 26th comment
Total: 26, showing: 1 – 20
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