[Gooshin]

i find #1 more pleasing to look at simply because it is better exposed, which leads to

a) more contrast, (and as we know, contrast in general makes things more appealing)

b) better noise control in the darker out of focus regions

if #2 was exposed identically i dont think anyone would be able to tell a difference.


as for the vote, i voted "who cares"

[Buddha Jones]

I'm changing my vote to, who cares?....He's been online and not provided the answer.

I agree...

[Tom M]

I say Number #1 is the Viv - In my experience, it is typically cold and offers a very smooth bokeh.. Number #1 is both colder and smoother than #2 so I say #1 is the Viv 105..

Now I want to know.. Can someone look at the EXIF and tell by the MTF data? Would the Pentax lens have MTF and the Viv not?

[Nesster]

I guessed Viv was 1 - due to the size of the oof lozenge for one, figuring a larger max aperture lens is the larger-gauge one, and therefore the bokeh will be larger-gauge as well.

[tybeck]

Sorry to let you guys stew. I was thinking about my answer and needed reminding (thanks Peter). The correct answer is: #1 was taken with the Vivitar.

Initially I posted this thread to help me decide which lens to keep and which to sell. From the reviews and comments I was reading I thought keeping the Vivitar would be the clear choice. However, from my test shots I can see that the Pentax is actually pretty good and the old adage that the lens doesn't make the photographer is very true. From the comments here I realize that I didn't everything into account to make the test a fair comparison between the lenses. k100d's comment was dead on. I'm new at this and focal fine tuning is an area where more practice is needed.

From my view the background on the Vivitar is smoother. I used the same exposure settings for both shots, but clearly they need to be tweaked for each lens. Not sure the best way to compensate for that. Maybe a common reference in the shot. I find the Vivitar exposure to be more pleasing as well. In the end you really can't go wrong with either lens.

I'm going to try these shots again and see if I can take care of the focus issue. Crops will be added and I'll add in a more complex back ground. I'll double check the white balance as well, it should have been correct for the bulb, but the colors do look off not that someone has mentioned it.

Thanks for all of your comments. The Vivitar is a keeper for me and I've learned a few things in the process.

[Tom M]

Hey - it's good to know I know my lens

[ftpaddict]

I don't even have it and I was able to tell.

[Nesster]

A question to those who have done more extensive comparisons than I have: I used the 'expansiveness' of bokeh on the Vivitar to identify it - partly because I'm familiar with the Takumar house tidyness, and partly on the theory that a larger diameter lens will produce larger diameter bokeh. Or maybe it's just that the Viv is in general a fleshy lens, sort of spilling out all over, while the Tak is leaner and a bit of an anal personality ... erm... a more precise personality.

Given equal quality lenses of the same focal length, where one is a 'compact' slow design and the other a larger fast one: are there image rendering characteristics that go with the design? Would the larger lens come with larger bokeh?

[Gooshin]

dont forget

the F/4 macro at wide open is a full circle

the F/2.5 at F/4 is going to be... octangular? (however many sides it has.. hehe)

therefore there will be fundamentally different bokeh in the images.



therefore i would suggest trying both at F/5.6 for a more definitive comparison. (do they have the same number of blades?)

[Nesster]

So an octangular (LOL) hole makes the oof blur spread out more?

What I'm trying to ask:
1) for a given f/stop, two lenses may actually have different diameter holes made by the aperture. This because one lens transmits more light and so needs to be choked down more to get the same amount of light on the film/sensor
2) the larger diameter lens, despite being set to the same aperture, has more 'room' for the light to travel inside, and so may produce a wider spread of oof fuzziness.
3) or is it simply a matter of how and how much spherical aberration has been corrected for?

None of the above would be a determining factor for me as to whether a lens is good or not, or whether or not I liked the bokeh in a given situation. It's just curiosity and search for information.

Plus, I think I've seen a similar effect between a fat 28mm Vivitar and a skinny 28mm Pentax.

[PENTAPSC]

Evidently, #1 was made with the Pentax, and #2 was made with the Vivitar!
Why? The Vivitar's larger wide-open aperture (f:2.5), stopped down to f:4, allowed a greater depth of field, as evidenced in the sharper leaf BEHIND the leaf in the left forefront of the picture. Color-balance, etc. is irrelevant, as the only comparison to the true inage is a comparison of the image with the real thing.
Anyway, that's my 2 cents (Canadian! )

[Gooshin]

So an octangular (LOL) hole makes the oof blur spread out more?

What I'm trying to ask:
1) for a given f/stop, two lenses may actually have different diameter holes made by the aperture. This because one lens transmits more light and so needs to be choked down more to get the same amount of light on the film/sensor
2) the larger diameter lens, despite being set to the same aperture, has more 'room' for the light to travel inside, and so may produce a wider spread of oof fuzziness.
3) or is it simply a matter of how and how much spherical aberration has been corrected for?

no

f 4 is f4

however f4 wide open and f4 stopped down are different..

just try it

take off both lenses and LOOK at them, leave the Pentax at wide open (f4) and stop down the vivitar to F4

you will seee that the size of the whole is the same, its just that the pentax one will be a perfect circle, and the vivitar will not.

the shape of the diaphram (shaped by the number of aperture blades) determines the shape of the bokeh, or the shape at which the image becomes blurry, which then impacts the overall image.

[Nesster]

yeah, I see that.

But I'm not talking about the shape or quality of the bokeh - I'm talking size.
In the two pictures, I think the first one has LARGER blurs than the second.

I propose 3 reasons, perhaps each points to the Vivitar being #1:
1) longer focal length produces greater out of focusness (focusity? ) and so a greater blur
2) more aberrations even stopped down cause a larger blur
3) the size of the front element/barrel means light from greater angles goes through the lens, even stopped down so the quantity is the same. Because of the greater angles, stuff gets fuzzier faster than with a smaller diameter lens.

This last one is the thing I'm obsessing about, because I'm thinking I must be wrong but can't figure out where I go wrong.