Interesting article on f1.4 versus f1.8


robbie_d

Link Posted 09/02/2011 - 14:25
Thought this might be of interest, given a recent thread was discussing the merits of f1.4 versus f1.8.

It centres around Canikon lenses but the general principle apply across brands.

link
If you can't say something nice about Pentax, you won't say anything at all.

Apparently.

Smeggypants

Link Posted 09/02/2011 - 14:59
Cheers. Interseting article.

The article is 'lab' based but then says ...

"The main reason I can see to invest in a 50mm f/1.4 is that the extremely narrow depth of field creates a very desirable effect that, in some circumstances, leads to a desirable look and feel that can’t be measured in the lab."

Which is exactly I bought an f1.2 and f1.4
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

robbie_d

Link Posted 09/02/2011 - 15:09
I know exactly where you're coming from Smeggy.

The lab can do many things but it can't measure the intangibles (Simga 30 f1.4 being the prime example).
If you can't say something nice about Pentax, you won't say anything at all.

Apparently.

johnriley

Link Posted 09/02/2011 - 15:19
I find it dosconcerting that any writer can put "depth of focus" when he means "depth of field" but that aside, this is an interpretation of results from DxO so not original research.

However, the basic message is correct. F1.7/1.8 lenses perform better than the f1.4 versions, at least in certain parameters. If you use the f1.4 for what it is intended for then it becomes superior to the f1.7/1.8 versions.
Best regards, John

robbie_d

Link Posted 09/02/2011 - 15:23
johnriley wrote:
I find it dosconcerting that any writer can put "depth of focus" when he means "depth of field" but that aside, this is an interpretation of results from DxO so not original research.

However, the basic message is correct. F1.7/1.8 lenses perform better than the f1.4 versions, at least in certain parameters. If you use the f1.4 for what it is intended for then it becomes superior to the f1.7/1.8 versions.

I wasn't aware I'd portrayed it as original research.
If you can't say something nice about Pentax, you won't say anything at all.

Apparently.

johnriley

Link Posted 09/02/2011 - 15:28
Quote:
I wasn't aware I'd portrayed it as original research.

Neither was I.
Best regards, John

cameraboy

Link Posted 10/02/2011 - 15:51
johnriley wrote:
I find it dosconcerting that any writer can put "depth of focus" when he means "depth of field" but that aside, this is an interpretation of results from DxO so not original research.

However, the basic message is correct. F1.7/1.8 lenses perform better than the f1.4 versions, at least in certain parameters. If you use the f1.4 for what it is intended for then it becomes superior to the f1.7/1.8 versions.


k7 10-17fe 12-24 55 100 macro 18-55 50-200

cameraboy

Link Posted 10/02/2011 - 15:57
well said John where do these strange phrases come from i was always taught from books or friends DEPTH OF FIELD not depth of focus etc
k7 10-17fe 12-24 55 100 macro 18-55 50-200

petrochemist

Link Posted 10/02/2011 - 17:49
cameraboy wrote:
well said John where do these strange phrases come from i was always taught from books or friends DEPTH OF FIELD not depth of focus etc

Depth of focus is a proper photography term, but it differs from depth of field.

IIRC It refers to the camera side of the lens, being the region in which the sensor/film can move without adversely affecting the results.
Mike
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.

.[size=11:].FlickrWPFPanoramio

johnriley

Link Posted 10/02/2011 - 18:17
Correct, there is a certain amount of depth of focus at the film/sensor plane. This allows for some error in the location of the film/sensor plane.

However, whereas smaller formats have more and more depth of field, they have less and less depth of focus. This means that smaller formats need higher standards of precision. This is where the 110 film cartridge and Kodak Disc formats fell down, with their cheap construction and tiny formats.
Best regards, John
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