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Tuesday, 24 November 2009

Comments

"First, a technical one: curiously, none of TOP's brain trust, including me, knew what should happen in theory to the maximum aperture of a fixed lens when a wide-angle converter is screwed on to the end of it.
It's always fascinating to discover the extent of one's own ignorance! However, experimentally we've determined that the maximum aperture of the GRD III's fixed 6mm (28mm equivalent) ƒ/1.9 lens doesn't change when the GW-2 wide-angle converter is used."

This amazed me first time I found out about it. My father showed me that the convertor for his olympus E10 and E20 did not change the aperture. Apparently it's a constant that an adaptor on the front doesn't change it but an adaptor between the body and the lens does. I don't know why though. I think the same was true of the telephoto adaptor too.

Hi Mike,
it is unfortunate that you were compelled to provide an explanation to an audience that would be expected to be more sensitive.

The worst example of an audience reaction that comes to mind was when, during a Bob Dylan Tribute performance on TV a decade ago.
Sinead O'Connor was booed off stage for her recent statements??????? at a BOD DYLAN TRIBUTE......
dale

Putting a teleconverter behind the lens extends the lens away from the body, in the same way bellows extension increases exposure time.

But that's obvious, no? Putting the adaptor in front of the lens, or behind it, I mean.

if you put the adaptor behind the lens, you're stuck with the same amount of light that enters the front, but captures a smaller part of that (since you're enlarging, you're cutting out the middle part of the image circle) to make your image.

If you're putting an adaptor at the front, you are able to increase the "light catchment area", by making the front element larger, and so maintain the same f-stop despite having a higher enlargement factor.

As has been widely observed, when it comes to web pages, few people read carefully. The problem with the Ricoh article was that its scope was described with mere words.

Still, it was completely obvious to me even with un-careful reading that the article was about getting a particular B&W look at ISO 1600. Hard to miss that, even for a web article. Not much there about shooting a child's Birthday party in color with flash.

--Marc

*Glossary Dept.: "Plastic art" means painting, drawing, sculpture, etc., not artworks made out of plastics.

Thanks for a good chuckle. Does the subtle sarcasm mean that you got very annoyed by those comments?

By the way, in italian plastic art means any art involving modelling in 3D, so sculpture, architecture, ceramics, glass and whatever, but not generally painting and drawing.

R.

OK TOP brain trust... we need answers!
Why is it a wide angle converter in front of the lens doesn't change the maximum aperature but a teleconverer behind the lens does? What happens with a front of the lens teleconverter?
Also (tee hee) what happens to depth of field?
bd

I really enjoyed looking at the pictures of Mitch's post. And I equally enjoyed reading Mitch's words.

His first sentence, "...for my work, the new Ricoh..." was interpreted by me as: "...for my job, the new Ricoh...".
I now feel silly to need Mike's post to remind me that his work is, well, his work!

Mike, you did a great job with your explanation! Made me laugh out loud.

Asides, I only recently discovered TOP and am daily reading further and further back into the archives. Having read about 40 pages of terrific readable and viewable stuff in the past two weeks, I'm now already afraid to find the 'last page' sometime soon...

Re night shots and automatic metering: what do you think of undereexposing by 1 ot 1.5 stops?

If it works it would allow a quicker response than spot metering, I think.

Seems intuitive to me. Put a telephoto adapter on the front of a lens and look at it. It magnifies the aperture so that it looks larger right? Put a wide angle adapter on the front of a lens and look at it. The aperture looks smaller right? Thus the F/stop is the same. If that sounds like gibberish, look at a 24mm f/2.8 lens and a 100mm f/2.8 lens from the front and compare the aperture sizes and you will see what I mean.

Look at the lens from the other side if you can and it looks the same both ways.

The same thing applies to teleconverters on the body side of the lens and for that matter if you ever play around with a convertable plasmat set you will see the same effect.

The non-intuitive explanation is beyond me in my un-caffeinated state.

I do agree with your basic point -- the article limited its conclusions pretty strongly, and most of the objections ignore those limits and thus criticize claims that were not made.

However, I also wish to express friendly amusement at your complaining that we're discussing the work rather than pixel peeping!

You'd like to this posts such as this one wouldn't be required. I guess that's the risk you take as the pool gets busier - someone is bound to pee in the water.

A teleconverter (which mounts between the lens and body) is enlarging the central part of the image to fill the frame, working entirely with light gathered by the original lens. Short of active night-vision technology, it's inevitable that the image when it gets done is dimmer. So that part is pretty clear to me.

I can't explain even to myself why auxiliary lenses that mount in front don't change the exposure, though. I've used a few, and the ones I've used in fact do not change the exposure; but I can't show the principle. I'm kinda hoping somebody eventually will explain it. (It seems like one COULD be built that DID reduce the light pretty easily.)

I just saw a big Picasso exhibition in Helsinki, of all places. One thing that struck me was how much pink he used! Lots and lots of ugly pink. Now, if only...

I think the reason that front add-ons don't alter the exposure is that they don't alter the lens-to-film distance. As you increase extension (I almost wrote 'bellows extension' there, but it amounts to the same thing) light loss occurs; with a close-up lens or an auxilliary lens of any sort that screws on the front, there's no extension increase.

I feel compelled to comment because your piece captures so well, so much that is human. And it made me smile.
However I haven't anything insightful to add. Only great restraint is keeping this short as well as superfluous.

Here's my response, it's short. I liked Mitch Alland's article. It was an interesting read. While I don't think I'm in the market for the Ricoh, apparently I didn't have to be to find the article interesting, since I read it twice and looked at the attached photographs carefully both times.

Oh and the photographs.
Frankly, while I liked some of the photographs Mitch Alland posted with the article quite a bit, it's also true some didn't quite hit me.

Which is also ok, since I think that has everything to do with me, and little or nothing to do with Mitch Alland. Or Ricoh.

Mike,
Thanks for the explanation that should not have been required,we humans are an odd lot,
disregard any backlash and remember an empty wagon makes the most noise.

Actually, I thought the pictures were fine. The only problem with them was that they look like they were taken with a cheap digicam. So while the conclusion that they produce the right look for his work is certainly valid, I disagreed with that conclusion. But that could very well be the look he wants, so, okay.

But it didn't make me interested in the camera, because in that case I think the camera was the limiting factor in the overall quality of the work.

The "size of the aperture" thing seems to be very convincing for a lot of people, and I should have thought of it (this isn't the first time I've heard of it). It's probably a good way to get people to mostly understand.

I don't remember it well because it doesn't work for ME; the visible size of the aperture from the front doesn't convince me of anything about the light-gathering power of the lens system.

Perhaps I'm just a bit thick. But Mitch's article seemed to be a bit of a wolf in sheep's clothing to me. It was presented as a casual camera review but was actually more of an exposition of Mitch's street photography. (When I enquired about seeing some unprocessed imagery from the camera Mitch instructed me to look elsewhere.)

So the fact that the piece drew commentary on Mitch's photographs seems perfectly natural, particularly here. Mitch invited a "referendum" on his work. The scope of his camera commentary was simply too narrow to be generally useful, in my opinion.

Dear folks,

There's a little bit of technical confusion going on, here. First, Mitch and Mike are talking about tele-extenders, not extension tubes. Tele-extenders aren't very thick and don't much change the distance from the lens to the film/sensor plane (well, not with long lenses, anyway).

The reason a tele-extender changes the maximum aperture is because it's changing the focal length of the lens without changing the amount of light it collects. In essence, it's just magnifying the existing image of the focal plane, spreading the same amount of light over a larger area. A 2X tele-extender magnifies the image by a factor of two, so the same amount of light has to cover four times the area. Voila, you've lost two stops.

Now, quick, tell me: If you put the converter IN FRONT of the lens instead of behind it, what happens to the light intensity at the focal plane?

Dunno!

It depends on how much light the new front elements are collecting and how they're funneling it to the original lens, and that wasn't at all obvious to the "brain trust" [ahem]. Collectively, it seemed to us that that was a matter of lens design and there was no way to say what would happen without referring to a specific converter. We weren't even entirely sure of that.

Simplest answer? Have Mitch run the experiment Mike referred to.

In the case of Mitch's lens and converter, the maximum aperture stays the same. That is NOT a generalizable statement. It's not obviously true of all front-converters.


~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
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If only Winogrand's horizons were straight. If only Witkin wasn't such a necrophiliac. If only Juan Buehler would shoot Tri-X. (This could get fun.)

how about this -- if only the cave painters in France would of had digital cameras

kman

For what it is worth I like the kind of work that Mitch does and have found his review very helpful. This article likely will push me to purchase the GRD III and finally give up some of my old 35mm cameras.

It is quite clear in his article that this "review" is based on the kind of work he does and is not universal. Too often we on the internet are willing to throw in our personal biases against someone else without trying to understand the basis of their position. In a similar vein I have seen some scathing comments about how James Whitlow Delano, whose style has some similarities, doesn't know how to take a good photograph.

These views seem to be most stringently held by the hobbiest, like myself. Just a curious phenomenon.

"how about this -- if only the cave painters in France would of had digital cameras

kman"

They wouldn't have gotten much painting done. Aside from the difficulty of applying paint with a camera, there would have been endless discussions on shooting test charts, pixel sizes, number of pixels that could or should be placed in a sensor.

I think Ken Tanaka's comment is spot on.

Dear Kent,

Hey, why not? They already had 'pigment' inks!
[vbg]

pax / Ctein

Mike, I still find it hard to believe that you can add a hunk of glass in front of that lens without causing a change in the light transmission. Did you by any chance check if the camera compensates for this by adjusting its ISO?

Dear Ken,

I most strenuously disagree. Mitch wrote a very straightforward column about why he found this camera more suitable for his particular style of photography. That is NOT a call for a judgment of his style of photography. In fact it's damned rude.

If I were to write a column on, say, the suitability of a digital camera I owned for doing my kind of Christmas light photography, I would be most offended if what I got back were comments to the effect of, "Well, that's all well and good, but your style of photography sucks."

All the more so, because you will never find a style of photography that is liked by the majority of people out there. It just doesn't exist. And you will always find a vocal minority who will criticize any particular style.

When work is being presented as work, per se, that's one thing. That's asking for comment and criticism. When someone writes an article talking about how a particular tool or technique is useful for the kind of work they do, that is NOT such an invitation.

It's not helped by the fact that most of the critics' remarks were ignorant and ill-informed. (No, that's not a subjective judgment: they were evaluating nuances from crappy little JPEG's. Give me a break!)

It may very well be human nature to do such things; that doesn't mean one has to approve of it.

As for Mitch honoring your request to see the unmanipulated photos, I would consider that request as out of place as if you asked to see one of my RAW files instead of one of my finished prints. That's not the art I want to present to an audience and that means it's frankly none of your business.

If I thought I'd get the kind of reception Mitch did illustrating my technique articles with my own photographs, I would frankly stop offering them.


~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
======================================

Mmmm? This quality thing is getting abit painful really. seems to me there are two ways to use the Q description - as an absolute measure, which must be something that everyone subscribes to the be of any use, or as a description of the nature of how something paints the image. In the latter case we might all prefer different qualities in our cameras. There seem to be a lot of humans who prefer to use their subjectively desired qualities as an absolute measure for everyone else.

So, Mitch likes his Ricoh. I like my (wife's different) Ricoh. My pictures don't look like Mitch's. That's all fine thanks. No contradiction and no problem.

Mike

Quite amusing...Rothko, Picasso and Mitch Alland...all in the same breath.

This is not my critique (I don't have a view), but what if one is aware of Mitch's intent / goal for this project, but after looking at Mitch's pictures, thinks that the GRD-III doesn't serve his intended function very well (or as well as other available tools)?

That would be fair game, no? That's how I read some of the comments, anyway.

Dear Richard,

Yes, Mitch held the ISO constant, and no, the transmission losses due to a few extra lens elements are NOT significant.

I suggest it's time to for you let this go and consider it an educational experience. You've learned something new about the way front converters can work. Simply be happy that you're now more knowledgeable than you were yesterday.

pax / Ctein

>>>Quite amusing...Rothko, Picasso and Mitch Alland...all in the same breath.<<<

Seems pretty reasonable to me...

Concerning comments on the pictures: I don't mind if people discuss them, but comments like "the composition is bad" or "they look like they were taken with a cheap digicam" are as useless as positive comments like the ubiquitous "great capture" — all they say is "I don't like your photographs", and, speaking of Picasso, are similar to people saying, "I don't understand abstract art, it looks like something my seven-year old could do with finger paint."

Getting useful comments, positive or negative on any photo forum is extremely rare. There are two long threads on my "Bangkok Hysteria" book project, which you can see on my flickr site: most of the comments, particularly at the beginning of the threads are off the wall. One poster was obsessed with the idea, believe it or not, that there were not enough smiling people in the book — not having understood that one of the main themes is the alienation of urban life in a huge, noisy and chaotic tropical city with the current difficult economic and political situation as a backdrop. Nevertheless, in these two very long threads I did get a few useful comments that helped me to edit down the number of pictures in the book.

Good negative comments are probably more difficult to make than positive ones.

The best critique I've ever received on a photographs is the following one by Steve Kessel:

http://www.l-camera-forum.com/leica-forum/digital-forum/29339-form-content-emotion-sean-reids-interview-3.html#post356195

And here is the photograph:

http://farm2.static.flickr.com/1047/1329990526_a9a13c6c1d_o.jpg

—Mitch/Chiang Mai

My take on a few of the issues:

First the technical:

A telecompressor (wide angle converter) mounted between the lens and the body is difficult to build and would obviously be impossible with a fixed lens camera like the GRD. However, this type of converter decreases the effective focal length (EFL) without changing the effective aperture. Therefore, the relative aperture (f-number), which is the ratio of the EFL/effective aperture diameter, is decreased. Ie, the lens speed increases.

With a wide converter mounted in front of the lens, the EFL is likewise decreased. The effective aperture, on the other hand, may stay the same, increase, or decrease, depending on the design. The only way to tell in practice would be through experimentation. The ones I have tested have, in general, decreased the lens speed. I have the GRD III wide converter but haven't been able to test it yet (damn work).

With regards to the second issue, my opinion is that anyone's appreciation of Mitch's work, or lack thereof, is irrelevant with regards to the topic of his post. Insights based on the image quality he presented may or may not be possible. While sharpness cannot (IMO) be judged from web-sized images, exposure latitude and tonal range deficiencies sometimes come across. I realize we're looking at 8-bit sRGB on any number of display types, but a look at a camera phone Flickr group pool is enough to show that it doesn't always take a print to show such deficiencies. Having looked at Mitch's work over the years, I think that I can actually see a difference in image quality in the small JPEGs he showed here, as compared to GRD I and II files processed using a similar workflow. In other words, if Mitch had provided the same examples and the camera had been a GRD II, I would have guessed ISO 800 rather than 1600.

Last, my take on the GRD III image quality is similar to Mitch's but perhaps to a lesser degree of enthusiasm. I feel that the GRD III RAW files have improved detail relative to noise at all ISOs and are more resilient during tone mapping than are the RAW files from the GRD II (which I likewise felt were an improvement on the GRD I RAW files). However, I don't think the improvement has been massive. I'd now put the GRD III in the same group as the LX3/D-LUX 4, Canon G10/G11, and Canon S90 in terms of sensor performance, whereas I feel that Ricoh's sensors in previous iterations were slightly behind those of Canon and Panasonic.

In case anyone is interested, I've just done a comparison of the Canon S90 and Ricoh GRD III detail versus noise performance: http://www.seriouscompacts.com/2009/11/iso-shootout-canon-s90-vs-ricoh-gr.html

Ctein, I didn't ask if Mitch had changed the ISO, I asked if the camera might have. Some cameras may have sensors that do such things (ie. change sensor sensitivity) when cued by the addition of a converter. But thanks for the education anyway.

Those of us who grew up with shooting large format are too well aware of mag factor when calculating the exposure. This is why when you add a converter or extension tube at the rear of the lens there is a change in the exposure, its a combination of the inverse square rule with light fall off when you increase the distance between the light source and the object, and the way aperture size is worked out as a logarithmic expression of the area of "hole" the light travels through. A front mounted converter does not change either of those, all it does is bend the light.

Regarding "...for my work..."

It's a shame you had to explain this.

MS

I still like to read about how photographers work with a specific "toy" (ahem tool). So let future contributors not be discouraged from sharing what they *think* than to pander to a "targeted" audience.

The optics geek point was quite interesting though, reinforced through years of 2x or 1.4x TCs n EXs that use a mod chip to enforce the numbers.

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