Should people use mm equivalence terminology?

**BigMackCam** · 10-08-2021, 06:16 AM - **2 Likes**

Originally posted by photoptimist

It's fully compatible with full frame film, but less so with full frame digital.

A number of very nice, compact primes from the film era have short exit pupil distances (the optical distance from the aperture in the lens to the plane of focus). When the lens is wide-open, the angle of refraction is so sharp, that some of the light from the lens bounces off the sensor instead of being captured by the microlenses on the pixels of sensor.

Technically speaking, it's not the main lens that is vignetting, it's the tiny microlenses. One could say that it is the camera that's not compatible with some full frame lenses!

The Jupiter-12 2.8/35 is another example... Excellent on 135 film (I've been told), but of limited use on a modern mirrorless digital camera for precisely the reasons you mention. However, rather than presenting as vignetting, in this case it results in colour-shift in the borders and corners...

Last edited by BigMackCam; 10-08-2021 at 07:34 AM.

Wheatfield · 10-08-2021, 08:32 AM - **1 Like**

Originally posted by clackers

UncleVanya, I think it's a pretty poor article, because it does not acknowledge that full frame means full frame lenses don't cover the image circle, that's the norm.

The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA*55 covers the full frame better than the FA50.

When I was looking at what lenses to sell when I ditched APS-C, I checked every DA lens I owned on the K1. None of the ones I had (I had all but a couple of the primes, and two of the zooms) gave especially good coverage on full frame. Those that didn't vignette more than I was willing to tolerate exhibited more corner softness than I was willing to tolerate. Some also had Sudden Death Motors which made them undesirable for reasons other than optical limitations.

BTW, the DFA*85/1.4 also has significant vignetting wide open, something that surprised me for what is a pretty expensive lens. It's gone by F2, but it's still there wide open.

D FA* 85/1.4 @ f1.4

D FA* 85/1.4 @ f2.0

**mikesbike** · 10-08-2021, 01:45 PM - **1 Like**

Originally posted by clackers

The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA*55 covers the full frame better than the FA50.

Right. I soon discovered the very noticeable light falloff wide open with the FA 31mm Ltd on my K-1 II. This was not shown as being this pronounced in tests, because these were done some time ago on APS-C bodies, which of course did not reveal the entire image circle. But unlike lenses which do not cover the entire image circle, the problem disappears very rapidly with even slight stopping down with this lens.

I have found the DA* 200mm f/2.8 performs quite well as a FF lens. It seems to have been taken bodily from the FA* 200mm design of the film era and upgraded with WR and SDM. It seems from reports this is also true of the DA* 300mm f/4 as well, maybe taken from the "A" version. I have the FA* 300mm f/4.5 which of course was designed for 35mm film and has exhibited no problems.

My DA 40mm f/2.8 Ltd definitely has more light falloff wide open for FF use as opposed to APS-C than does my FA 43mm Ltd at f/2.8- which is negligible, but will improve as stopped down. Both are very fine lenses for either use.

**yucatanPentax** · 10-08-2021, 01:54 PM - **1 Like**

Originally posted by BigMackCam

The Jupiter-12 2.8/35 is another example... Excellent on 135 film (I've been told), but of limited use on a modern mirrorless digital camera for precisely the reasons you mention. However, rather than presenting as vignetting, in this case it results in colour-shift in the borders and corners...

That actually sounds like it might be kinda cool, depending on the effect given. Maybe I'll try one some day
Argghhh.... too many lenses.

Update: well, looks like it comes in a Kiev / Contax mount and M39 Leica mount. If there's an M42, I didn't find it. Whew... LBA / GAS dissipated for now.

**BigMackCam** · 10-08-2021, 02:04 PM - **1 Like**

Originally posted by yucatanPentax

That actually sounds like it might be kinda cool, depending on the effect given. Maybe I'll try one some day
Argghhh.... too many lenses.

Update: well, looks like it comes in a Kiev / Contax mount and M39 Leica mount. If there's an M42, I didn't find it. Whew... LBA / GAS dissipated for now.

I wasn't aware of the Kiev / Contax version, but the LTM version is a rangefinder lens... short registration distance, and a rear element that comes alarmingly close to the film / sensor

It's a lovely lens, and actually works well with B&W photography on my A7 MkII... but I know it would perform a lot better away from the frame centre on film...

**clackers** · 10-11-2021, 10:45 PM

Originally posted by Wheatfield

BTW, the DFA*85/1.4 also has significant vignetting wide open, something that surprised me for what is a pretty expensive lens. It's gone by F2, but it's still there wide open.

Sure. Even the Sigma 85mm Art was noted by Optical Limits as having a 1.8eV drop off in the corners. That's not just light level of course, it will mean detail's missing, too. And it affects the bokeh - more catseye at the edges instead of perfectly round.

tradigi · 10-12-2021, 08:19 PM - **1 Like**

It's helpful to know the equv. or more to the point the factor. However, IMHO knowing the change in angle of view of a particular focal length (in degrees) is of more value if you're speaking in purely technical terms. Because in the end, what I'm really concerned with (besides depth-of-field or lack thereof) is coverage.

**Graville** · 10-13-2021, 12:34 AM

Even if you’re resolutely in the first camp, when you buy a new lens for your APS-C camera I bet you’re doing the conversion factor in your head anyway so don’t pretend it’s of no use lol.

**Rondec** · 10-13-2021, 02:22 AM

Originally posted by Graville

Even if you’re resolutely in the first camp, when you buy a new lens for your APS-C camera I bet you’re doing the conversion factor in your head anyway so don’t pretend it’s of no use lol.

I actually started my photographic journey shooting digital APS-C and so when I finally got a K-1 I was actually doing a reverse conversion -- figuring out what lenses I needed to match the ones I liked on my K-3. I don't do it any more for either camera, but I think the big thing is comparing to what you are used to shooting. If someone hasn't used full frame, using full frame equivalent focal lengths means very little to them.

Fogel70 · 10-13-2021, 06:40 AM

As FF EQ focal length been used on many small sensor fixed lens cameras including smartphones it is not only affecting those that have been, or are using FF format.
These small sensor cameras have been marketed using FF EQ focal length since beginning of digital photography.

If anyone know what focal length their smartphone use, they probably give you FF EQ focal length if you ask them, not the actual focal length.

**Alex645** · 10-13-2021, 12:55 PM

Originally posted by Fogel70

If anyone know what focal length their smartphone use, they probably give you FF EQ focal length if you ask them, not the actual focal length.

If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths.

I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide".

normhead · 10-13-2021, 01:33 PM

Originally posted by Alex645

If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths.

I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide".

So, if you posted to Flickr it wouldn't give you the focal length above the exif?
The FL in Pentax cameras is listed both as the true focal length and the 35mm equivalent in my PP software, and in Exifextreme.

**UncleVanya** · 10-13-2021, 02:07 PM

Originally posted by Alex645

If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths.

I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide".

13mm, 26mm, 77mm equivalent. In that short simple statement I bet a lot of people now clearly understand the field of view better than ultrawide, "normal", and telephoto.

Smartphone "normal" has been around 28mm for a long time. Telephoto typically has meant 50mm which is hardly telephoto by any stretch of the imagination.

**Alex645** · 10-13-2021, 02:54 PM

Originally posted by normhead

So, if you posted to Flickr it wouldn't give you the focal length above the exif?
The FL in Pentax cameras is listed both as the true focal length and the 35mm equivalent in my PP software, and in Exifextreme.

The context of my comment was regarding smartphone lens focal lengths.

Yes, there are many ways we can find the focal length via metadata. I'm just saying in context, most people shooting with their phones couldn't tell you what FL they shot at nor care.

With some effort, they could tell you but in my experience as a photographer, the only time I felt compelled to share or even know the phone's FL was when I has printed images and needed the info as signage in a gallery along with name, title, date, etc.

slartibartfast01 · 10-13-2021, 02:55 PM - **1 Like**

Originally posted by Alex645

Yes, there are many ways we can find the focal length via metadata. I'm just saying in context, most people shooting with their phones couldn't tell you what FL they shot at nor care.

With some effort, they could tell you but in my experience as a photographer, the only time I felt compelled to share or even know the phone's FL was when I has printed images and needed the info as signage in a gallery along with name, title, date, etc.

I suspect most people using phones don't know what focal length is.

10-08-2021, 08:32 AM - 1 Like	#107
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by clackers UncleVanya, I think it's a pretty poor article, because it does not acknowledge that full frame means full frame lenses don't cover the image circle, that's the norm. The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA55 covers the full frame better than the FA50. When I was looking at what lenses to sell when I ditched APS-C, I checked every DA lens I owned on the K1. None of the ones I had (I had all but a couple of the primes, and two of the zooms) gave especially good coverage on full frame. Those that didn't vignette more than I was willing to tolerate exhibited more corner softness than I was willing to tolerate. Some also had Sudden Death Motors which made them undesirable for reasons other than optical limitations. BTW, the DFA85/1.4 also has significant vignetting wide open, something that surprised me for what is a pretty expensive lens. It's gone by F2, but it's still there wide open. D FA* 85/1.4 @ f1.4 D FA* 85/1.4 @ f2.0 Last edited by Wheatfield; 10-08-2021 at 08:39 AM.

10-12-2021, 08:19 PM - 1 Like	#112
tradigi New Member Join Date: Mar 2021 Posts: 7	Helpful In Some Respects It's helpful to know the equv. or more to the point the factor. However, IMHO knowing the change in angle of view of a particular focal length (in degrees) is of more value if you're speaking in purely technical terms. Because in the end, what I'm really concerned with (besides depth-of-field or lack thereof) is coverage.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Nature Isle aux Coudres @ 28 mm, 45 mm and 63 mm FL with DFA 28-105 mm HD and f/16.	RICHARD L.	Post Your Photos!	6	02-25-2022 05:25 AM
The bogeyman will catch you: equivalence, magnification and noise/dynamic range ;-)	beholder3	General Photography	41	10-28-2019 05:47 PM
Ming Thein on format equivalence, engineering and practical envelope	Unregistered User	General Photography	41	06-19-2018 10:35 AM
For Sale - Sold: Brand New FA 31 mm, FA 77 mm, DA* 60-250 mm, DA* 300 mm	ppkkcao	Sold Items	14	11-02-2014 08:42 PM
Equivalence? 300mm/2.8 plus a 1.7X TC	jpzk	Pentax SLR Lens Discussion	10	09-28-2010 08:09 AM

10-08-2021, 06:16 AM - 2 Likes	#106
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,674	Originally posted by photoptimist It's fully compatible with full frame film, but less so with full frame digital. A number of very nice, compact primes from the film era have short exit pupil distances (the optical distance from the aperture in the lens to the plane of focus). When the lens is wide-open, the angle of refraction is so sharp, that some of the light from the lens bounces off the sensor instead of being captured by the microlenses on the pixels of sensor. Technically speaking, it's not the main lens that is vignetting, it's the tiny microlenses. One could say that it is the camera that's not compatible with some full frame lenses! The Jupiter-12 2.8/35 is another example... Excellent on 135 film (I've been told), but of limited use on a modern mirrorless digital camera for precisely the reasons you mention. However, rather than presenting as vignetting, in this case it results in colour-shift in the borders and corners... Last edited by BigMackCam; 10-08-2021 at 07:34 AM.

10-08-2021, 01:45 PM - 1 Like	#108
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	Originally posted by clackers The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA55 covers the full frame better than the FA50. Right. I soon discovered the very noticeable light falloff wide open with the FA 31mm Ltd on my K-1 II. This was not shown as being this pronounced in tests, because these were done some time ago on APS-C bodies, which of course did not reveal the entire image circle. But unlike lenses which do not cover the entire image circle, the problem disappears very rapidly with even slight stopping down with this lens. I have found the DA 200mm f/2.8 performs quite well as a FF lens. It seems to have been taken bodily from the FA* 200mm design of the film era and upgraded with WR and SDM. It seems from reports this is also true of the DA* 300mm f/4 as well, maybe taken from the "A" version. I have the FA* 300mm f/4.5 which of course was designed for 35mm film and has exhibited no problems. My DA 40mm f/2.8 Ltd definitely has more light falloff wide open for FF use as opposed to APS-C than does my FA 43mm Ltd at f/2.8- which is negligible, but will improve as stopped down. Both are very fine lenses for either use.

10-08-2021, 01:54 PM - 1 Like	#109
yucatanPentax Loyal Site Supporter Join Date: Dec 2009 Location: Dallas / Yucatan Posts: 1,840	Originally posted by BigMackCam The Jupiter-12 2.8/35 is another example... Excellent on 135 film (I've been told), but of limited use on a modern mirrorless digital camera for precisely the reasons you mention. However, rather than presenting as vignetting, in this case it results in colour-shift in the borders and corners... That actually sounds like it might be kinda cool, depending on the effect given. Maybe I'll try one some day Argghhh.... too many lenses. Update: well, looks like it comes in a Kiev / Contax mount and M39 Leica mount. If there's an M42, I didn't find it. Whew... LBA / GAS dissipated for now.

10-08-2021, 02:04 PM - 1 Like	#110
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,674	Originally posted by yucatanPentax That actually sounds like it might be kinda cool, depending on the effect given. Maybe I'll try one some day Argghhh.... too many lenses. Update: well, looks like it comes in a Kiev / Contax mount and M39 Leica mount. If there's an M42, I didn't find it. Whew... LBA / GAS dissipated for now. I wasn't aware of the Kiev / Contax version, but the LTM version is a rangefinder lens... short registration distance, and a rear element that comes alarmingly close to the film / sensor It's a lovely lens, and actually works well with B&W photography on my A7 MkII... but I know it would perform a lot better away from the frame centre on film...

10-11-2021, 10:45 PM	#111
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by Wheatfield BTW, the DFA*85/1.4 also has significant vignetting wide open, something that surprised me for what is a pretty expensive lens. It's gone by F2, but it's still there wide open. Sure. Even the Sigma 85mm Art was noted by Optical Limits as having a 1.8eV drop off in the corners. That's not just light level of course, it will mean detail's missing, too. And it affects the bokeh - more catseye at the edges instead of perfectly round.

10-13-2021, 12:34 AM	#113
Graville Site Supporter Join Date: Jul 2019 Photos: Gallery Posts: 21	Even if you’re resolutely in the first camp, when you buy a new lens for your APS-C camera I bet you’re doing the conversion factor in your head anyway so don’t pretend it’s of no use lol.

10-13-2021, 02:22 AM	#114
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	Originally posted by Graville Even if you’re resolutely in the first camp, when you buy a new lens for your APS-C camera I bet you’re doing the conversion factor in your head anyway so don’t pretend it’s of no use lol. I actually started my photographic journey shooting digital APS-C and so when I finally got a K-1 I was actually doing a reverse conversion -- figuring out what lenses I needed to match the ones I liked on my K-3. I don't do it any more for either camera, but I think the big thing is comparing to what you are used to shooting. If someone hasn't used full frame, using full frame equivalent focal lengths means very little to them.

10-13-2021, 06:40 AM	#115
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 3,062	As FF EQ focal length been used on many small sensor fixed lens cameras including smartphones it is not only affecting those that have been, or are using FF format. These small sensor cameras have been marketed using FF EQ focal length since beginning of digital photography. If anyone know what focal length their smartphone use, they probably give you FF EQ focal length if you ask them, not the actual focal length.

10-13-2021, 12:55 PM	#116
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by Fogel70 If anyone know what focal length their smartphone use, they probably give you FF EQ focal length if you ask them, not the actual focal length. If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths. I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide".

10-13-2021, 01:33 PM	#117
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by Alex645 If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths. I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide". So, if you posted to Flickr it wouldn't give you the focal length above the exif? The FL in Pentax cameras is listed both as the true focal length and the 35mm equivalent in my PP software, and in Exifextreme.

10-13-2021, 02:07 PM	#118
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by Alex645 If you look up the new Apple iPhone 13 Pro Max, under specs, they only define the three lenses as telephoto, wide, and ultra wide. They do state the f/stops and the optical zoom amount, but no reference to focal lengths. I do use my smartphone to take photos, but I couldn't tell you what the focal length is nor the FF equivalence. I can guess and I can research it, but if asked, I'd just say it's "wide". 13mm, 26mm, 77mm equivalent. In that short simple statement I bet a lot of people now clearly understand the field of view better than ultrawide, "normal", and telephoto. Smartphone "normal" has been around 28mm for a long time. Telephoto typically has meant 50mm which is hardly telephoto by any stretch of the imagination.

10-13-2021, 02:54 PM	#119
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by normhead So, if you posted to Flickr it wouldn't give you the focal length above the exif? The FL in Pentax cameras is listed both as the true focal length and the 35mm equivalent in my PP software, and in Exifextreme. The context of my comment was regarding smartphone lens focal lengths. Yes, there are many ways we can find the focal length via metadata. I'm just saying in context, most people shooting with their phones couldn't tell you what FL they shot at nor care. With some effort, they could tell you but in my experience as a photographer, the only time I felt compelled to share or even know the phone's FL was when I has printed images and needed the info as signage in a gallery along with name, title, date, etc.

10-13-2021, 02:55 PM - 1 Like	#120
slartibartfast01 Pentaxian Join Date: May 2015 Photos: Gallery Posts: 1,931	Originally posted by Alex645 Yes, there are many ways we can find the focal length via metadata. I'm just saying in context, most people shooting with their phones couldn't tell you what FL they shot at nor care. With some effort, they could tell you but in my experience as a photographer, the only time I felt compelled to share or even know the phone's FL was when I has printed images and needed the info as signage in a gallery along with name, title, date, etc. I suspect most people using phones don't know what focal length is.