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11-07-2010, 02:12 AM   #16
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QuoteOriginally posted by Jonathan Mac Quote
I take your point, and maybe I came across as brusque in that statement. I think that everyone has a different point at which normal progressive softness when opening the aperture actually becomes "soft". The 85/2 is certainly no softer wide open than most lenses, but I see a fairly big sharpness difference between f2 & f2.8. It is certainly usable wide open, maybe even very useable, but these are all subjective measures. The blue fringing does also have the effect of reducing sharpness, by blurring lines that out to be clean. For me, as the longer focal length usually gives ample subject separation even at f2.8, that is where I usually use it. I do agree that itīs a marvellous lens: colour, contrast, "3D pop" are all there, wide open or not.
to put it into simpler terms, rather than saying soft, it is much appropriate to say the variation or difference in sharpness between f2 and f2.8 is a big leap. this is both increase in lpmm resolution and increase in depth of field (area in focus). in other words, a transition from a sharp state to sharper. as far as soft to sharp transition is concerned, there are other lenses that are suited with the soft at wide open notion.

11-07-2010, 05:07 AM   #17
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QuoteOriginally posted by hoojammyflip Quote
I've got to do some lens consolidation. As the winter months draw in, so I thought I'd see the benefits of the f2 aperture on my 85mm for indoor portraits. In reality, even with fast film (I've gone retro), I am getting down to silly slow apertures where my new baby boy just goes into a blur. I've come to the conclusion a flash or two will have to be purchased. Plus, I really need f5.6-f11 when close up in order to get satisfactory depth of field.

I've got an issue now with which lens to keep and which to get rid of. My 85mm's advantage over the 100mm is that its a little shorter, a bit closer to normal, so that you don't notice the tele effect, but also that its got that lovely great front element, like a doey eyed dog. Aside from that, its twice the price of my 100mm, which buys a lot of nappies and beer.

Which would people keep of the two?

(I've got the same problem now with the 2.8/40 and 2.8/35, but am decided on that already...the minimum focus distance of the 35 wins out over the 40)
I have the M82/2 and the A100/2.8 (which is the same otically as the M100/2.8). Clearly the 85 is the better of these two lenses, not only faster, but a better performer, especially on digital (for some reason that is not clear to me). M/A100 is also clearly surpassed by the K105/2.8, which is the best Pentax 100mm option (not counting macro 100 mms). This does not say the M100 is a bad lens, it is just not as good as the 85/2 (or 105/2.8). You will easilly sell any of them, but of course you'll get more for the 85.

Me I wouldn't sell any of them, but save up for a flash. Well, I would sell the M100, but only because I have the A100.
11-07-2010, 09:57 AM   #18
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Used to own the M 100 2.8, and it's definitely a lens to seek out. But the M 85 f2 is my favorite.

These shots are all wide-open - more than sharp enough at that aperture, but DOF is tiny at many distances you'd typically be shooting it at:


.




Below is a crop:

11-07-2010, 10:21 PM   #19
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Between the M85/2 and a 100/2.8 (I have a 85/2 and F100/2.8), I'd certainly keep the M85/2. Easier working distance, shallower DOF, faster, small, light.
Typically, if I need to get closer with a M85 I simply attach a 25mm segment of an extension tube. Not 1:1 macro, but good enough for many shots.
My F100/2.8 only seem to get dedicated macro duty.

11-10-2010, 07:49 AM   #20
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Well, I have just shot the lenses side by side, hoods, tripod, tape measure etc.

The 85mm is defo a nice lens, but at f2.8 I think the 100mm is just as sharp. There is not a lot in it in terms of FOV, MFD etc.

See for yourselves, but I am going with the 100mm!
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11-10-2010, 08:07 AM   #21
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Your results definitely show that the 100 is sharper wide open than the 85 is, but that both are more or less equal at 2.8. As I said, thereīs a dramatic improvement in this stop from the 85mm. But if both are equal at f2.8, why not keep the 85 and you have the extra stop if & when you need it? On the other hand, as their M lenses, useability wide open makes the Av mode much more useful.

I would encourage you to spend an afternoon shooting genuine photos, not test scenes, with each one to see which one you like, which gives you more flexibility etc.

I donīt envy your choice, TBH. I think Iīll keep both of mine...
11-10-2010, 08:09 AM   #22
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QuoteOriginally posted by Douglas_of_Sweden Quote
M/A100 is also clearly surpassed by the K105/2.8, which is the best Pentax 100mm option (not counting macro 100 mms). This does not say the M100 is a bad lens, it is just not as good as the 85/2 (or 105/2.8). .
Hhhmmm. Well up to a point. I have the M100/2.8 and the K105/2.8 (mine's one of the ones pictured in the database). Stopped down I don't think there's much in it. At 2.8 the M is without a doubt sharper, and suffers from less longitudinal CA. In contrasty light the K can produce some very unpleasant reddish and greenish fringing. Although with the right subject matter that slightly veiled, soft-edged look wide open can be effective. I can't bring myself to sell either of them, although it's ridiculous to have both.
12-14-2010, 05:28 AM   #23
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QuoteOriginally posted by Jonathan Mac Quote
I would encourage you to spend an afternoon shooting genuine photos, not test scenes, with each one to see which one you like, which gives you more flexibility etc.

I donīt envy your choice, TBH. I think Iīll keep both of mine...
Just came back from having taken some low light photos, where there was specular light from windows in the background. It was a civil wedding ceremony, so I was being discrete not using flash...had to shoot wide open and only had the M100. ISO 1600 Neopan.

Some thoughts come to mind, buyers remorse et al, but its impossible to shoot the scene again with the M85 so drawing definite conclusions is unfair on the M100. 1) it would have been possible to have an extra stop of performance with the M85 to get rid of camera shake (I was shooting on the cusp of "acceptable" shutter speeds) which means my pics are robbed of ultimate sharpness 2) I have not done any specular highlight/bokeh testing of the M85 to see whether its not vulnerable to donuts...I am guessing that maybe within all this old Pentax blurb there is actually some truth to this and background highlights will end up look nicer thanks to the M85's undercorrection. 3) get a bigger camera bag and take more lenses with me.

On the donut bokeh front, looking at jshermans photo of the dinosaur skeleton further up the thread, it does appear that the 85 suffers less from this phenomenon than something like my 50/1.7.

I only had the 28/35/50/100 and the 85 would have been a good accomplice. I can see I will end up keeping the 85/135 lenses which I thought I would sell! Still, my collection of primes is miles cheaper than some of the individual Zeiss manual offerings, so I dont feel too guilty!

Fingers crossed, will still have a decent pic for printing and framing, I dont envy wedding photographers at all, having to churn out a 100 or so.


Last edited by whojammyflip; 12-14-2010 at 05:39 AM.
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