[Anvh]

Oblique angles of light is the main culprit. This was never a problem for film - as emulsion is essentially flat and very capable of accepting light from severe angles. My understanding is that pixels are not flat, and need to have the light hit more directly. I assume this is the reason why many lenses that work well on film (for instance some DA lenses on FF film bodies), have severe light fall off issues on digital. The measurements of light loss beyond f/1.4 are pretty significant, at more than half light loss. Some sensors in the test show a full stop of light loss.

They indeed explain it like that but thinking about it... it means that the center of the sensor where the light hits straight on shouldn't be effect, only that the vignetting will get worse

[drougge]

They indeed explain it like that but thinking about it... it means that the center of the sensor where the light hits straight on shouldn't be effect, only that the vignetting will get worse

That would be true if the lenses had a point in the middle where the light came from. But fast lenses tend to have large rear elements, and the light from the edges of those won't be getting in in the center pixels.

I don't think there's any optical reason you couldn't construct lenses without this problem though. (Large almost flat rear elements where the light emerges almost completely from the position it will end up in. Likely this would lead to strange bokeh though.)

[Anvh]

I believe digital lenses are designed to make the light as straight as they can.
It was one of the reasons they made the 24mm and 25mm for the 645D first because the wide angle film lenses didn't preform that great like they did on film

[verdigris]

I suppose if you like the soft watercolor look that comes with photos taken at f/1.4 or greater on digital sensors - or you just want to say you have a lens faster than f/1.4 - then there is no rational argument against that.
.

You should check out some of the fujinon machine vision lenses. These are tack sharp at 1.4, so long as you nail the focal plane - no soft watercolors. There is a wide variety of lens designs out there, and it seems to me it's the particular lens design (and the quality of the construction) more than any of it's associated numbers that defines how it will perform. The Q is the only camera out there that will let you experiment with essentially any lens that was ever made.

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Last edited by verdigris; 04-08-2013 at 09:06 AM.

[Rob22315]

You should check out some of the fujinon machine vision lenses. These are tack sharp at 1.4, so long as you nail the focal plane - no soft watercolors. T There is a wide variety of lens designs out there, and it seems to me it's the particular lens design (and the quality of the construction) more than any of it's associated numbers that defines how it will perform. The Q is the only camera out there that will let you experiment with essentially any lens that was ever made.

Wow, you guys are incredible with this kind of information. Any suggestions on which converters to buy? I guess there's D mount, CS mount, and C mount so I assume there are Q mount converters for all of these? Are any one of these better to start out with?

RG

[verdigris]

starting with a C-mount converter is probably the best place to begin.

[hnikesch]

Don't look for CS mount lenses as nobody makes a CS to Pentax Q adapter

Hans

[Rob22315]

Don't look for CS mount lenses as nobody makes a CS to Pentax Q adapter

Hans

I thought I saw a CS to C adapter, has anyone tried combining the two? Also I noticed the Novoflex adapters go for $150 while the Fotodiox adapters go for $10. Is there a $140 difference between the two?

[hnikesch]

I thought I saw a CS to C adapter, has anyone tried combining the two? Also I noticed the Novoflex adapters go for $150 while the Fotodiox adapters go for $10. Is there a $140 difference between the two?

An adapter is available to put C lenses on a CS camera but not to put CS lenses on a C camera. I built an adapter to put a 2.5mm CS lens on my Q by altering a D to Q adapter but the CS lens protrudes into the Q body and depresses the lens contacts in the body, I had to insulate the back of the lens but it works. see link below.

Hans

https://www.pentaxforums.com/forums/pentax-q/211126-cctv-2-5mm-cs.html#post2231522

[Travis Butler]

starting with a C-mount converter is probably the best place to begin.

I'd actually recommend a D-mount. The good D-mount lenses aren't quite as cheap as the Fujian 25/35mm C-mounts you can find on fleabay, but my favorite D-mounts are significantly sharper, not to mention much smaller and lighter - a perfect companion to the Q.

The biggest overall problem I've had with D-mounts is that a lot of them are fixed-focus, and only one of the ones I've got focuses correctly to infinity on the standard adapter. Which means you'll either have to focus by unscrewing the lens from the adapter, or shim the lens with paper. On the whole, I'd recommend going for a lens with adjustable focus instead.

Some of my favorite D-mounts:

Elgeet 38mm f/1.9 - I've got a fixed-focus version and a couple of different focusable versions of this lens, and they're excellent - very sharp at the center and good contrast. Main liability is a bokeh-like softness around the edges, going very blurry in the corners; I usually like the effect, framing the subject, but if you want sharpness across the frame you'd probably want a different lens.

Kern-Paillard Yvar 36mm f/2.8 - these show up fairly often on fleabay, and they're a nice sharp lens - not quite as sharp IMHO as the Elgeet in the center, but better uniformity across the frame. The main drawback (at least on my copy) is the colors are somewhat flat compared to the Elgeet.

Kern-Paillard 12.5mm - this is available as both a Switar f/1.5 and a Yvar f/2.5. Both are sharp when in focus and have good color; but aside from the wider aperture, the Switar is focusable, while the two Yvars I have are fixed-focus. Apparently not all the Yvars are fixed-focus - I've seen some listed that aren't, if the pictures can be trusted - but most of the ones I've seen are. I'd strongly recommend looking for one that focuses.

Som-Berthoit Lytar 12.5mm f/1.9 - Very similar to the Switar 12.5mm, almost as nice; I'd give the Switar a bit higher marks, though that may just be my copy. I definitely had to clean mine; at first the center was very washed-out.

Wollensak Raptar 25mm f/2.7 - Tiny little lens, even more portable than the K-P and Lytar 12.5mm's. Not quite Elgeet-level sharp, but still very sharp. Main drawback, aside from the relatively slow aperture, is flare; you'll definitely want to shield this one, a problem that the 25mm C-mount Cosmicar I also own doesn't have.

[Pioneer]

This is one of the things I love about the Q, the ability to adapt so many different types of lenses to it.

And the regular lenses are pretty darned nice all on their own. The 02 Zoom as a few problems but even that one is pretty good.

I use my Q to do everything my DSLRs will do and if I'm careful I get some beautiful out of focus blur and some wonderful 11x17 prints using Perfect Resize.

I know a lot of people love to shoot long telephoto shots but most of my work has been a bit more "normal." For one, I have found the Sonnetar 25/1.1 to be an amazing portrait lens. With a Cowboy Studios radio trigger mounted in the hot shoe I can easily control two or more flash units in various configurations.

It isn't for everyone but it is a very, very flexible system. To say it cannot replace a DSLR is a trifle short sighted, it really depends on what your needs are, and maybe more importantly, what your own preconceptions are.

[madskillz06]

http://www.flickr.com/photos/pentaxricohsg/sets/72157633893372656/

I love referring to this link and his photos.. The Q has enough power to deliver anything if you know what your doing and if your creative enough to give it a try.

[hoffo]

wow very nice photos there.