T stop difference EF35 1.4 and EF 35 2.0 please

[jamesdb_db]

I am considering the Canon EF 35 1.4 (11 Elements) and 35 2.0 (7 Elements)

lenses. However I could not find any T stop information on them. I understand

that there is also a loss of light due to the 20D microlenses on the sensor

which takes effect as you go to larger apurtures.

 

Could I ask kindly if someone with both lenses could take identical manual

pictures with the EF 25 1.4 at f/1.4 and EF 35 2.0 at f/2.0 with the shutter

speed set at 1 stop difference to compensate for the aperture difference and

tell me how many stops the two pictures vary in brightness?

 

My guess is that the 35 1.4 might get me only 1/2 stop more light?

 

I thank you in advance

 

JamesDB

[mike butler]

...I don't know James,

 

It's unlikely anybody would have both of these lenses. The 35/2's clunky autofocus and poor

sharpness at about f/4 and under (at least in my experience) was enough to sell it back to

keh without worrying about light transmission.

 

I say get the 16-35 L and be happy...

[peter_foiles2]

Despite Mikes comments I own both lenses. The MUCH smaller and MUCH lighter 35/2 is more suitable in some situations. I consider the 35/2 one of the more undrrated Canon lenses.

 

T stops? argh, there are more important things to worry about and whats the microlens stuff? Pick one and go take some interesting photos.

 

Oh and photo.net if I think more than one ? is appropriate I do not appriciate you telling me otherwise.

[tommyinca]

My 35/2 is sharp at f2 and near sensor resolution limit at f2.8. IMHO, one may have to pay throught the roof to find a better 35mm (from any makers) as good as Canon's 35/f2.

[PuppyDigs]

<P><I>It's unlikely anybody would have both of these lenses. The 35/2's clunky

autofocus

and poor sharpness at about f/4 and under (at least in my experience) was enough to sell

it back to keh without worrying about light transmission.</I></P>

 

<P>I guess you don't hang with too many photogeeks! Plenty 'o folks own both lenses. In

fact,

it's

very common to have extremely redundant lens collections. Until last month I had six

50mm lenses, 3 EF and 3 Nikkors, as well as 5 "normal zooms" and 4 telezooms. I finally

got off ma duff and sold most of them!</P>

 

<P>Unlike you, my EF 35 2.0 (early 90s vintage) is decent at F2 and sharpens up nicely by

2.8.

It certainly blew my EF 50 1.4 USM outta the water (it didn't get decent until F5.6). Also, I'd

characterize AF as quiet (not silent), peppy and surefooted. It snags focus faster

and more reliably than my EF 50 1.4 USM and EF 50 1.8, especially in low light.</P>

[mars c]

Hello James, I dont understand what the T in T stop means. What I understand from your question is that you want to find out how much faster or brighter the expensive than a camera 35mm 1.4 against the affordable 35mm 2. the answer is the 1.4 is twice as fast or bright compared to the 2. The 35mm 1.4 is gonna get you 1 whole stop more light, not just 1/2. Why? it has something to do with the aperture bieng round and not rectangle or a straight line.

[jamesdb_db]

I was hoping someone could take the time to do test for me. Maybe Peter since you seem experienced? I know to some this question may seem a bit nit-picky, but for me it's an important factor. I wish Canon would simply list this data as they do for their film lenses but they don't leaving me to guess. If you don't have the time for everything maybe someone could simply take the pictures and post them up with exif info, and I'll compare them in Canon's software.

I do think this is a valid consideration when one looks at $1000+ lenses.

 

JamesDB

[jimstrutz]

Mars, T stops are the common measurment of actual light transmission, not the theoretical F stop. Since the f/1.4 has more elements it might not be a full stop faster in light transmission. T stops are commonly used in high end video and movie lenses where extremely long zoom ratios require lots of elements in a lens. It was also more of a factor before better lens coatings came along.

[jamesdb_db]

Hi Marsc

 

Actually this is not the case. f stop is a theoretically derived number for a lens but you would see that it's not necessarily the actual light hitting the sensor. Take two different lenses at a given fstop like the 70-200 2.8 and say an 85 prime. Take a picture with both lenses on manual same ISO, Aperture and Shutter speed on a tripod with fixed lighting conditions. You will see that the 70-200 should be slightly less bright due to a number of things like more elements the light travels through. This holds with f stop unless Canon does some t stop fudging somwhere.

 

JamesDB

[roger krueger]

Does anyone know how t-stops are determined? Is it a point measurement at the center of

the image, or is it an average over the image area?

 

Put another way, does does a lens with dead-even illumination have the same t-stop as

one with the same central brightness but a lot of falloff?

[yakim_peled1]

>> my EF 35 2.0 (early 90s vintage) is decent at F2 and sharpens up nicely by 2.8.

 

My EF 35 2.0 (2002 vintage) was very good at F2 and excellent at F2.8.

 

>> I'd characterize AF as quiet (not silent), peppy and surefooted.

 

My mileage vary markedly. My copy had very sluggish AF.

 

Happy shooting,

Yakim.

[mars c]

I'm sorry James, I totally misunderstood your main question, for it is only now that i heard about T stop. Actually I have no idea what is brighter between the two 35mm lens. I'm aware though that my prime is much brighter than my zoom, when I tested them wide open and shutter speed compensated. But never wondered why, because what i was looking for at that time were distotion, color and contrast differences. I may not have the answer but Your question enligntened me, James, I thank you for that.

[lovcom_photo]

Peter, are we a bit touchy on this subject?

 

By the way, why on earth would anyone one keep the 35mm F2 if they have the much better 35 F1.4L?

 

Riddle me that, sir.

[bill_fouche]

Dan: because if you prize a light-weight rig, the 35/2.0 is far superior. Slap one on an XT, for example, and you can walk around with the thing all day long, have terrific optics and a roughly "normal" field of view, and not notice that you are carrying much of anything. That is simply impossible with the immense and clunky 35/1.4.

 

To those (few) whose 35/2.0 is not pin-sharp at wider apertures, send it back or get a new one. It's a terrific lens. One of my favorites.

[brad_w]

James, no one talks about T stops because, as another poster said, they are largely

irrelevant in the days of modern multi coating. Keep in mind that the microlenses are

integral to the sensor so have already been incuded in the ISO calibration. In addition to

that, Canon calibrates their ISO's about 1/3 stop hot (ISO 100 is actually about 125) and

Canon dslr's are fantastic at 1600 and 3200.

 

But let's assume your calculations are correct and the T-stop of the f1.4 lens is 1.7 Like

wise the T-stop of the f/2 lens will be greater than 2...maybe 2.2 or 2.1, but for

argument's sake let's say it's really f/2. Anyway, 1.7 at 1600 will give an exposure at night

under street lights of about 1/20. Now worries, hand-held. f/2 puts you at about 1/15 -

you'll need to be a little careful, might get a miss or two, but totally workable.

 

I guess what I'm saying is that the fraction of a stop you are stressing out about is

negligibe. There are many many great reasons to get the L lens -color, contrast, handling

build quality - but they may not be the right ones for you. The f/2's a great lens. -B

[ron c sunshine coast,qld,a]

The T stop question is very relevant.

<P>For example i've seen test examples (with histograms) that show the 85/1.2L to be much brighter over the 85/1.8 than the numbers suggest

<BR>Usually one would suspect super fast lens numbers to be 'fudged' a little but apparently not allways

[sheldonnalos]

I believe I have lens comparison tests saved somewhere that I did while I owned the 35mm f/1.4 and 35mm f/2 at the same time. Unfortunately, they are on my other computer and I won't have access to it for a couple weeks.

 

If the question is still important to you, send me an email (through Photo.net) and I'll check if I have the image files when I have access to them.

 

FWIW, I found the 35mm f/1.4 to be a noticeably better performer and I sold the 35mm f/2. I dont think that there will be a significant different in T stops (i.e. I recall that both lenses when shot at the same aperture/shutter speed gave similar exposure levels). Also, I had not heard any complaints regarding digital sensor/microlens performance when shooting wide open.

 

I'd say buy which ever one suits your purposes, and you can afford. I would not worry about T stops, unless you are planning to modify it to be a cine lens.

[jamesdb_db]

Thank you Sheldan for lending me a hand. I appreciate the thoughtful comments from the members; although while they discuss if my question bears any merit no one has so far offered to help me out :)

 

I am certainly leaning towards the 35L 1.4 however I did want to understand its nature in this regard. I was hoping they could both be shot wide open so all the glass comes into play with shutter speed being moved a stop to compensate.

 

JamesDB