Why does high t stop start to get soft ?

[Scot Yount]

Michael,
Thanks very much for pointing that out. I read that article about six months ago and absorbed just enough of it to "understand" shutter angle, but now, really understand it much better. There is no substitute for going out and screwing something up to increase your usable knowledge--that is for certain!

 

[PatrickFaith]

My general belief is that you can stop down more with zooms, maybe because they aren't that fast and are telephoto lenses at the long end... But then, usually if I'm at the 290mm end of an Optimo at f/16, I'm shooting close-ups, not wide shots...

I have a related question, I use 2x and 1.4x PL extenders a lot but I get confused how they modify my "f" stop range when I put them on. My main problem is if I put a 2x PL extender on what is my new appropriate T stop range and the "f" stop depth of field change.

On the Pl x2 for example, when I put that on at T2 50mm anamorphic master prime, I get two stops of light reduction and often need to move my lens to T2.8 because it softens it a bit. So if my normal range on the MP is T2-T8, when I put the 2x extender on I'm finding I like it between T3-T9 setting on the lense. So with the additional two stops on the extender I think my new effect range is T5-T11 (on the lense ring it's T3-T9). I'm really not even sure what all this has done to my depth of field.

So I'm finding what you said about zooms, about the same for what I find for extenders (i.e. I can stop down a bit more with extenders and often have to step down 1 anyway). Is my thinking totally off?

 

[David Mullen ASC]

Probably at the long end of the you can stop down further but I worry about the wide end of the zoom where you have more issues with resolution and back focus -- while at the long end, you're fighting for more depth of field and are usually shooting close-ups where you might not notice a hit in resolution from diffraction.

I don't use extenders much at all, maybe three times in twenty years actually, so my experience is limited but you'd think you could see the issues on an HD monitor. Last time I used an extender was on the 24-290mm and we saw that dust trapped inside the elements of the extender was coming into focus.

 

[Michael Tiemann]

The diffraction equation is independent of depth of field and also independent of clear aperture (according to http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm). If you are imaging a true point source of light, it doesn't matter whether your Optimo is at 24mm or 290mm, and it doesn't matter whether your T2 anamorphic is as-is, coupled to a 1.4x, or coupled to a 2x teleconverter. If the lens is perfect (which few are) and if you are peeping pixels one at a time (which few do), you can notice diffraction as an emergent phenomenon at f8, stronger at f16, etc.

Ansel Adams was a founding member of the f64 club. He made 8x10 negatives that he would often blow up to make 16x20 prints. Here's an article from Bob Atkins that explains why photographers making 8x10 prints (15 lp/mm * 254mm = 3810 lp or 7620 pixel resolution) can get away with f180, why 35mm tops out at f22, and why APC-C (basically 5K RED resolution) tops out at f16: http://bobatkins.com/photography/technical/diffraction.html

 

[Elsie N]

Not much to add to this interesting thread except something I saw on a PBS series about the photographers sent out by the New Deal administration during the Great Depression. One of the people in the show stated that whomever was the person in charge of photographers always reminded them when they went out into the field to "shoot f11."

They were black and white photos but really tell the story of that time, even today.

 

[PatrickFaith]

Probably at the long end of the you can stop down further but I worry about the wide end of the zoom where you have more issues with resolution and back focus -- while at the long end, you're fighting for more depth of field and are usually shooting close-ups where you might not notice a hit in resolution from diffraction.

I don't use extenders much at all, maybe three times in twenty years actually, so my experience is limited but you'd think you could see the issues on an HD monitor. Last time I used an extender was on the 24-290mm and we saw that dust trapped inside the elements of the extender was coming into focus.

That makes a lot of sense, also when i shoot at the longer part I'm also doing primarily close ups. I think the diffraction can actually be a bit of nice effect on close ups too (Phil was commenting on the creative use of diffraction), so shooting long on closeups makes sense that I can go to a higher f stop.

[btw I don't like using extenders but I shoot over long time periods, primarily since I don't know what I'm doing and have to reshoot scenes over months of time. Thus I have bought a few really good lenses, and use the extenders because I can't afford a complete set of master primes. ]

The diffraction equation is independent of depth of field and also independent of clear aperture (according to http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm). If you are imaging a true point source of light, it doesn't matter whether your Optimo is at 24mm or 290mm, and it doesn't matter whether your T2 anamorphic is as-is, coupled to a 1.4x, or coupled to a 2x teleconverter. If the lens is perfect (which few are) and if you are peeping pixels one at a time (which few do), you can notice diffraction as an emergent phenomenon at f8, stronger at f16, etc.

Ansel Adams was a founding member of the f64 club. He made 8x10 negatives that he would often blow up to make 16x20 prints. Here's an article from Bob Atkins that explains why photographers making 8x10 prints (15 lp/mm * 254mm = 3810 lp or 7620 pixel resolution) can get away with f180, why 35mm tops out at f22, and why APC-C (basically 5K RED resolution) tops out at f16: http://bobatkins.com/photography/technical/diffraction.html

Makes perfect sense that the lens mm difference doesn't matter.
I find the interesting thing on the bobatkins site is the close focus vs infinite focus actually does effect the usable F-stop range, and this appears to be lens specific. My testing lines up with Atkins comments on the infinite focus for high quality lenses, for those keep to the lower range of the F-Stop range: "Sharpness slowly drops as the lens is stopped down past f8. f16 is OK and f22 may be acceptable, but f32 is pretty bad."

Not much to add to this interesting thread except something I saw on a PBS series about the photographers sent out by the New Deal administration during the Great Depression. One of the people in the show stated that whomever was the person in charge of photographers always reminded them when they went out into the field to "shoot f11."

They were black and white photos but really tell the story of that time, even today.

In San Francisco I've enjoyed a lot of the New Deal artwork which is still up in it's original form(i.e. postal building on mission & stuart near the Ferry Building). I'll look for that show.

 

[Anton Shavlik]

edit: nvm, answered in the links above

But, lens design is far from the ideal lens where diffraction is only affected by f number, as written about in the links above. I do think you should test a lens rather than assume.

 

[Michael Tiemann]

Patrick, in a different article, the Cambridge Color folks address close-focus vs. infinity focus in this article: http://www.cambridgeincolour.com/tutorials/macro-lenses.htm

Scroll almost to the bottom or search for "MACRO DIFFRACTION LIMIT" in the article.

 

[Ketch Rossi]

Each set of lenses, be it Still Glass or Cine Glass, Super Speeds or Standards, amongst which then you need to take consideration for actually more then just two speeds.

What I have found the most interesting is that while Zooms do act differently as they some how seem less sensitive to diffraction at the long end, is also to be said that zooms, are usually already softer all together at the wider end, meaning less sharp, yet when shooting Portraits or insuring that the subject been photographed is closer then anything else to the Sensor while all back ground further out as to let the subject been isolated, then the results have always been really good.

As for Primes, I have seen so many variables thru the years, from Still glass of 35mm FF to MF, and I have seen MF glass been more susceptible to the rule of Diffraction, and as for the Cine primes, I have of course to quote the Master Primes as been the absolute best of the ebbing, actually better still then some new comers which were supposed to bring the price hone, which they did in a way and they did;t in another, talking about Summilux's here...

So Master Primes, years and years later still remain truly an incredibly well design set of lenses, and while I enjoyed shooting WO with them most if the time, I really never went over T11, simply because they kind of lost their magic by then, not because of Diffraction, which did started to appear under the microscope, and remained absolutely pristinely clean thru T8, my favorite stop has always been T4 on them, and almost shot everything WO when allowed, with all else shot T2.8 or T4...

 

[PatrickFaith]

edit: nvm, answered in the links above

But, lens design is far from the ideal lens where diffraction is only affected by f number, as written about in the links above. I do think you should test a lens rather than assume.

I've found I need to basically retest everything when I change an element of my rig. In vdslr land I basically used the test from the websites, but as I've been getting better I've found I can use the website tests less and less. I started off scarlet with canon lenses(kind of close to what the websites said), then moved to epic monochrome with RPP (here i started really needing to test things myself), now dragon with master primes I need to do specific tests for my specific configuration. I think the major film guys know they need to test/choose the best tool for each film, but people like me that have moved into this from vdslr land haven't really developed the rigor to do specific tests per project.

Patrick, in a different article, the Cambridge Color folks address close-focus vs. infinity focus in this article: http://www.cambridgeincolour.com/tutorials/macro-lenses.htm

Scroll almost to the bottom or search for "MACRO DIFFRACTION LIMIT" in the article.

This is excellent, perfectly explains why you can increase the f-stop as you start to close focus. I had not idea the "effective" f-stop was changing as I went to close focus based on the internal mechanisms (this is lens manufacturer based ... I see that my nikon lenses auto correct this, no idea what Arri cine glass does).

Each set of lenses, be it Still Glass or Cine Glass, Super Speeds or Standards, amongst which then you need to take consideration for actually more then just two speeds.

What I have found the most interesting is that while Zooms do act differently as they some how seem less sensitive to diffraction at the long end, is also to be said that zooms, are usually already softer all together at the wider end, meaning less sharp, yet when shooting Portraits or insuring that the subject been photographed is closer then anything else to the Sensor while all back ground further out as to let the subject been isolated, then the results have always been really good.

As for Primes, I have seen so many variables thru the years, from Still glass of 35mm FF to MF, and I have seen MF glass been more susceptible to the rule of Diffraction, and as for the Cine primes, I have of course to quote the Master Primes as been the absolute best of the ebbing, actually better still then some new comers which were supposed to bring the price hone, which they did in a way and they did;t in another, talking about Summilux's here...

So Master Primes, years and years later still remain truly an incredibly well design set of lenses, and while I enjoyed shooting WO with them most if the time, I really never went over T11, simply because they kind of lost their magic by then, not because of Diffraction, which did started to appear under the microscope, and remained absolutely pristinely clean thru T8, my favorite stop has always been T4 on them, and almost shot everything WO when allowed, with all else shot T2.8 or T4...

Agreed on the master primes, basically in the past I was randomly doing wrong things but it all came out in the wash, plus I was shooting for 1080p so things effectively summed down. Shooting with master primes and the dragon is just a much sharper tool, and I need to learn to not cut myself and go through all the bad habits I've picked up as I have been learning.

 

[Elsie N]

@ those of you who have shot stills either professionally or in a professional way, but also shoot motion... do you set up your camera differently or just treat motion as moving stills?

 

[Ketch Rossi]

@ those of you who have shot stills either professionally or in a professional way, but also shoot motion... do you set up your camera differently or just treat motion as moving stills?

While I usually just pull frames from Motion as the cameras gets set up for Motion...

When still Pulling has priority then I wold set up the camera for stills accordingly, including Shutter Angle, Shutter Speed and compression, which is to the absolute lowest the camera can handle in the given resolution & frame per rate settings combo.