ryszard_stasinski1

Stefan,

<p>

You are absolutely right about bogus tests in some photo journals.

For example, I can show you that some very popular tests in a German

magazine are sometimes totally misleading, I can provide examples

and a little bit lengthy explanation what probably is the reason.

The one of two only trusty methods of scientific lens testing is

measuring of MTF curves for frequencies not higher than 40 lp/mm,

but after experience with this bogus test I am now collecting

warnings even against the MTF test (they are some!). Note that

e.g. maximum frequency test could be misleading, too - two lens

with frequency limits e.g 90 lp/mm and 120 lp/mm may behave in

exactly the same manner for less than 40 lp/mm, being in this way

undistinguishable in practice.

<p>

The other scientific method is based on statistics - you should

find few dozens of cooperative lens users, provide them a

questionnaire in which they evaluate the lens, and conclude with

some statistical processing of the answers. This is very cumbersome,

so hardly anybody do it. The results are more 'fuzzy' than those of

MTF test, but they are some advantages, too, e.g. you can ask for

unmeasurable features like ergonomics, and you avoid problems with

lens variability.

<p>

Notice that evaluations on this forum are close to the statistic

test - somebody describes a lens, somebody else agrees or disagrees,

and after a while an image builds up.

<p>

Nice shooting with the (tested or untested) lenses!

<p>

Ryszard

Really interesting thread.

<p>

I'd like to add four more warnings concerning lens testing:

<p>

14) Lenses have different performances for far and near objects,

so does the test results.

<p>

15) Maximum lp/mm lens resolution is always somewhat subjective.

You are dealing with fuzzy, low-contrast microscopic images, and

your definition of 'maximum resolution' is likely to be somewhat

different from somebody's else.

<p>

16) Test results are strongly dependent on the target contrast.

<p>

17) Use of B&W emulsions may lead to overestimation of lens

performance in color photography. Namely, B&W emulsions are

somewhat 'blind' to red light (red is dark in B&W), while because

of physics laws response to the red light is usually the Achilles'

heel of optical systems.

<p>

Saying all that I must conclude that lens comparisons are both

_interesting_ and _useful_, at least for me. An example - without

reading them I would never know that these oversized

point-and-shot-like cameras holding the name 'Fuji' are so valuable

pieces of equipment.

<p>

Not everybody can manage to have (and compare) two or more MF

systems, a word from those who can may help a lot.

<p>

Ryszard Stasinski

Hi everybody,

<p>

I would like to comment on DOF of different formats. Namely, under

some reasonable assumption DOF for different formats is the same!

These assumptions are:

<p>

- _proportion_ of COF to negative (linear) size is constant, and/or

- _proportion_ of diffraction distortion to negative size is constant.

<p>

For example, if you shoot with ideal 50mm lens for 35 format at f=11,

and ideal 100mm lens for 6x7 at f=22, then the FM negative seems

just as the 35mm one enlarged two times: enlarged image details but

also enlarged distortion, including two times greater blur due to

out-of-focus at any distance. Theoretically, the negatives would

give prints of exactly the same quality, in fact MF print will be

better because of better proportion between film granularity and

image detail sizes, and because of lower distortions of enlarger

lens (lower magnification).

<p>

However, everybody of us loves the possibility of going much

further with in-focus sharpness/contrast for larger format lens,

in particular hesitate to use larger f-stops on MF than on 35 mm

format (at least I hesitate). And this costs DOF, of course.

<p>

Saying all that I strongly disagree with a statement

that 6x4.5 is the greatest reasonable format for landscape

because of DOF. In fact, the larger the format, the greater

freedom in compromising between DOF and in-focus sharpness.

<p>

Ryszard Stasinski

I really doubt that Kiev lenses have no multicoating. I have several

Carl Zeiss Jena lens for MF and 35 formats, and some (post-)Soviet for

35 mm. I am using them through converters on Mamiya M645, and

Canon EOS 10. Except for one or two _all_ of them are multicoated,

some being up to 20 years old. I have been considering the purchase

of 250/5.6 for Kiev 60 - it has an abbreviation 'MC' in its name,

what do you think, what does it mean?

<p>

My experience with flare in East-European lenses is quite good. For

example, Biometar 120/2.8 MC for Pentacon 6 (and Kiev 60) seems to be

not worse from this point of view than Mamiya 645 80/2.8 N, but

Sonnar 180/2.8 MC is not so good. Coating of post-Soviet 20/3.5 for

35mm cameras is quite good, too. BTW Biometar was CZJ name for

Planar (5-element), CZJ had no rights to this name.

<p>

Kiev fish-eye has a very good reputation. The name for Kiev

standard lens is Volna. I have a 35mm format Volna-9 50/2.8 for macro.

This is my sharpest lens at around f=8!

<p>

General opinion is that unless you have no luck Kiev lens

represent very high value for money, the price of a converter

included.

<p>

Hope this helps.

<p>

Ryszard

I don't agree that smaller grain is the only advantage of MF. There

are also some optic laws that make it 'better' than the 35 mm format.

At the same time this text explains why an optically worse MF lens

may appear to be _more_ efficient than an optically better 35 mm one.

<p>

I'll try to explain it on the following example: You are

photographing a Greek/Roman temple (or a court building in your city)

on a bright sunny day. The building is surrounded by grooved coulmns

which grooves produce dense and contrasty pattern of parallel lines

on your negative/slide. You have at disposal two cameras: Pentax K1000

and Pentax 67, two lenses: 50 f1.7 for K1000, and 105 f2.4 for 67, and

a converter that allows you to use the 105 lens on K1000.

<p>

So, you do three shots using: K1000 with 50 lens from the distance of,

say, 30m (100 feet), K1000+converter+105 from the approximately

double distance - 60m (200 feet), finally 67 with 105 lens, the

distance is rougly 30 m, once more. As can you see, the chosen

distances guarantees identical composition of all three shots.

<p>

Results? You measure the 'K1000+50' transparency and discover that

when comparing to the measurements on the columns the contrast

between bright and dark parts of grooves on the transparency

is diminished by... really don't know what number to say... 7%,

O.K.? Don't ask me _how_ to measure this, just assume that this is

possible. Then you take the 'K1000+105' transparency. The 105 MF

lens is not so well corrected as the 50 mm 35 format one, so, the

lines on the transparency are 'smeared' stronger than those on

the 'K1000+50' one. You measure that the contrast is diminished by...

once more a wild guess... more than for 50mm, of course, but not too

much... 10%? Finally, you take the MF transparency. The first

discovery is that the lines on it are two times wider, so their

'smear' by the 105 lens is much less disturbing than on the 35mm

format transparency. And now you can observe the intervention of

laws of optics - as the lines on the MF transparency are two

times less dense than on the 35mm one, the reduction in their

contrast is roughly two times smaller, too. So, you measure only

5% of contrast loss, 2% _less_ than for K1000+50mm!

<p>

Please, don't take too seriously all this percents. I want only

to illustrate the fact that the larger film allows you to get _more_

sharp and contrasty images even if your optics is _less_ efficient

than that for the smaller film format, and that this could have

nothing to do with film granularity.

<p>

Ryszard Stasinski

The negative grain enlargement is only half of the reason for better

MF "better tonality". Another one is lens performance. If you have a

line pattern on a 8x10 picture of density 1 line pair per mm, then

this makes 8 lines per mm on 8 times enlarged 35 mm negative while

only 4 lines per mm on the 4 times enlarged 6x7 negative. If you take

_any_ lens, a 35mm or an MF one, it is diminishing contrast

approximately proportionally to the pattern density. This means that

if contrast attenuation for 8 line pairs per mm is 10%, than it is

only 5% for 4 line pairs per mm. Simply, for exactly the same shot

done with the same aperture and top-class lens the contrast lost of

any feature for 6x7 negative is two times smaller than for 35 mm one.

<p>

Ryszard Stasinski

Thank you to all for very interesting answers. The very points for me

are that this is a sort of LF but lighter, and that this camera will

last forever, so, the 'bargain' body and 3 'ex' lens for not much

more than 1000$ will be probably working for years.

<p>

Ryszard Stasisnki

More precisely - why this is not a succesfull MF system for landscape

photography? It is light (much lighter than e.g. Fuji 680),

affordable (slightly more than 1000$ for camera plus 65/105/180 lens

at KEH), has full movements (Fuji 680 is restricted in this domain),

and gives really big pictures - 6x9!

<p>

This question is triggered by an answer to 'Horseman 6x9' question -

it is suggested that Fuji 690 may be a better buy. Horseman is

skipped over in virtually all overviews of MF for landscape in

favor of Pentax 67 (SLR but not movements, approx. the same weight

and price for a system, smaller neg), Mamiya rangefinders (portable

and light, but in all other respects Horseman seems to be better),

and Fuji line, including even the expensive and _heavy_ 680. Why?

<p>

I never worked with groundlasses and view cameras - maybe here is

the answer?

<p>

Regards to all

<p>

Ryszard Stasinski