jimdesu

Um... To say it differently:

 

1. With a "normal" round lens, the focal ration is the focal-length of the lens divided by the diameter of the aperture of the lens. If the lens has a rectangular profile instead of a circular one?

 

2. Is there a specific relationship between resolution and/or the on-axis mtf curve as a function of the number of grooves per inch of the Fresnel lens?

 

// James

Hi there,

 

I've got a pair of weird questions about Fresnel lenses that I was

hoping someone could answer me with.

 

1. How does one compute the effective F/ ratio of a square lens?

 

2. Is there some kind of deterministic relationship between the

number of grooves per inch and the effective contrast/resolution

relationship for the lens besides "more is better"? =)

 

thanks,

 

James

He fixed mine up and it works much, much better. And he's really cool, too.

Yes, I read it. But that was a while ago and some things got lost when I moved a few months ago (some of my computer stuff among them). Thanks for the info -- I'll be able to figure it out from there. =)

I pushed the ink button on front of the printer and watched the led's race back & forth, but no avail. Is there a different way to do the nozzle check?

Hi there,

 

After an hour or three tweaking the contrast & color of a landscape in Photoshop (including soft-proofing to my Epson 2200 under "relative colorimetric", I finally got set to print out my picture and call it a night. I was quite surprised to see a magenta & blue picture come out! All the places that should've been green were blue, so I'm surmising that I'm getting no yellow output from the printer. This is in spite of a full yellow cartridge and the fact that just a few months ago I printed just fine with the same cartridges (and the printer's been covered up during the duration, so no weird environmental factors). Has anyone seen behavior like this before?

 

thanks,

 

James

You can get into medium format without spending a ton of money, and, if you are happy using a rangefinder camera, you can get something that's not any much harder to use than a 35mm. As another enthusiastic amateur, I find that it's great to use the 35mm for snapshots since the film's so inexpensive, and to use the MF when I'm trying to make "art" (whatever that is -- maybe I'll know once I've done it.) The moskva mentioned above, or a Super Ikonta are both excellent and relatively cheap ways to get into MF. Especially if you go this route, you may find yourself growing to love the way the older rangefindrs force you to make focussing and composing two separate steps.

 

just $0.02

Well, maybe, but for the price of these things used, it's tempting -- my concern is if the vignetting would become serious enough so as not to cover the negative or not....

 

// James

'allo all,

 

Question for anyone familiar with wide-angle (non-fisheye) auxiliary

lenses. Is there a limit to how wide one can go with these? If I

put a .42x lens on front of a 20mm lens, will this really give me an

8mm lens, or will I get something else instead?

 

thanks!

 

James

Hi there,

 

I've heard a lot of info regarding lpmm ratings of various 50mm lenses that one can mount on a Pentax 35mm, but very little about contrast & color. Does anyone know how a 50mm f/4 flektogon (medium-format wide-angle) stacks up in terms of contrast & color? I currently use SMC 50/2 and a Pancolar 55/1.2.

 

Thanks,

 

James

Wow! KEH has always been fantastic to me -- I'd buy another lens from them in a heartbeat. Your predicament is far closer to what I expect from Adorama than KEH -- I'd given them another shot.

 

// James

Anyone know where there's any MTF data for the old Takumar lenses like the 200/5.6?

 

Thanks,

 

James

My old man knows someone who used to cross-process Kodak 5071 with good results: has anyone done so for EDUPE?

 

thanks!

 

James

Hi all,

 

Does anyone know if modern Pentax-dedicated flash units will work with an LX body?

 

Thanks!

Hi there,

 

Is Impressa the slowest, least grainy color print film out there, or can someone recommend something less grainy? I'm scanning at 5760dpi & enlarging to 13x19, so I'm fighting a LOT with the film grain. At this point, I'm not too concerned as to contrast as I can change that within reason via masks and gamma adjustments on the scanner.

 

Any opinions or religious beliefs would be appreciated. If it would help, I could even go to a reversal film if it isn't too saturated.

 

Thanks,

 

James

I've run film through a bunch of places in town, and these guys always seem to give the best results (including some obvious and well-called for dodging on some small prints that I hadn't requested -- good call on the printer's part).

 

There's also something to be said for funnelling cash through your local good guys even if it costs a little more -- think of it as insurance that they'll still be there later on.

Although I don't worship at the church of Zeiss, their Flektogon 20mm lens is outstanding. Also, you can find a (not as good) tilt-shift lens made by Arsat for cheap. The optics aren't as good as the Zeiss (though they're not bad), but it's amazing what you can do with tilts.

Outstanding lens; often I find it's a little too sharp for portraits of women. I never gave it much respect until I reviewed some older photographs I took back when I was still trying to figure out contrast, and was totally surprised with how sharp the darn thing is.

 

Regardless of which other lenses you've got (I live by my 55/1.2), this one's a good one to hang onto.

 

=)

I'm searching to replace my dropped sekonic 608 (if anyone found one

without a case at stinson beach just north of san-francisco, please

lemme know), and I've run across a new offering called the 558.

Does anyone know what the differences between these two meters is?

Does the 558 support EV metering and other goodies?

 

Any help would be appreciated.

 

James

If you can find a K2 (or K2 DMD), it's a good grab -- basically a K1000 with extra bells & whistles (exposure comensation, MLU, DOF preview and aperture-priority).

I use 55/1.2 and 50/1.2 lenses, and bear in mind that while you get the advantage of thinner DOF and more speed, they're not remotely as shart as the good old 50/2 lens. If you're shooting something where you really want the detail (not a head-shot portrait!), make sure you hang on to the old 50/2.

 

The speed difference is negligible, but if you like carpaccio-thin DOF, then a f/1.2 or f/1.4 is worth it.

One of the great things about using M42 lenses on Pentax beasties is that if you've got one of the continuously-variable-aperture lenses (there're actually a lot of them), it makes shutter-priority work really easy. Sometimes, when you're hand-holding, this can be a real boon.

 

just $0.02

Hi there,

 

Is there any two-bath developer for use with C41? I want the control that the first Stoeckler bath gives, but I don't want to give up my XP2 to have it.

 

Thanks,

 

James

They're not exactly elegant, but I get great results from mine (an RB Super D). Top shutter speed is 1000, which, if your DOF selection isn't critical, I find helps the clarity for hand-held work.

 

Plus, while they don't have any in-built metering, you can compose with the lens open and the camera will stop it down automatically when you make your exposure. You still have to cock it open for the next one, but it's really handy.

Yeah, but it's still inverted sideways. I actually find it easier to pan around when it's upside down and my brain just goes backwards than half-inverted/half-not-inverted.

 

I've an RB Super D, and the mirror is bright wide open, but if you have to stop-down for DOF checks it's DIM. Luckily that's not too often.

 

I totally agree. I saw that pitiful attempt at a clone that Wisner's come up with. The thing about the Graflex that makes it so wonderful is that the camera automatically stops down the lens at exposure-time. If you've gotta stop the lens down manually, you might as well buy a rangefinder.

 

$0.02