General Knowledge on Photography

Q: Do we really need protection filter attached on our lenses all the time?

A: I always use the protection filters. They are always attached on every of my lenses. I only take my filter off when I need highest quality. There are times you got to take off your protection filter. It really produce sharper pictures. Example: Night Scenery.

Q: Which protection filter is the best? Do I get better result if I use the manufacture's filter?

A: Recently Chasseur d'Image performed a test on UV-filter coatings which should be identical to lens coatings:

Q: It seems that everyone uses a skylight filter. Is this the same as a UV filter?

A: The Skylight and the UV is not really the same. IMHO, the skylight is more suitable for most of the works. Difference brand produce difference color balance. For HOYA Skylight, It produce more warm color (pink). And the HOYA UV is more to yellow. So I use the UV for close-up of flower and so-on. But if you are uncertain, get the skylight in-stead.

For skylight / UV filters' color balance as well as quality references, please refer to:

http://www.cmpsolv.com/photozone/filter.htm
http://i31www.ira.uka.de/~klaus_s/filter.htm

Q: Which PL Filter is the BEST??? If money is not a matter. Does the Canon and the Nikon version really better than the third party one???

A: If money doesn't matter I would suggest the B&W MC PL Kaesemann. It has a top reputation but it's also extremely expensive. Overall I don't think that Canon filter are so good - the coating is maybe average but surely not superb. Nikon & Hoya HMC PLs seem to be very good. These comments were based on magazine reviews. Personally I own an extra thin Hoya PL "Super" with HMC coated rear glass. Seems to be fine. ( Klaus, 10 Mar 1997)

Q: What does Canon ‘L’ lenses, Nikon ‘ED’, APO, LD glass in practical mean?

A: Canon's 'L' mean using APO elements mean better color, richer color, more saturated color and better open aperture performance.

Q: I do have one question though regarding the flash. It's about flash compensation. In what situation would you need it? It's the flash power that the camera control right? I don't understand why anyone would want to under/over-expose the subject.

A: The under/over exposure will be greatly useful when you use spot metering or when your metering is located at something too bright or too dark. Example, when I use spot metering and the spot fall on my friend's white t-shirt, I got to over expose it 1 stop. And when the spot metering fall on pure black t-shit, I got to under-expose 1 stop. Whatever the spot fall on, the camera will try to expose it to 18% gray. So with normal exposure, white will not turn out white and so do black will not be black.

Q: Why people use external power supply for their external flash? Anything better when using the power supply?

A: You are right! When I use 4 AA 800mA NiCad batteries with my Canon 540EZ, a full recycle time for a full flash is about 6 seconds. Not to mention this performance only can last less than 2 rolls of film (it depends on how one use the flash too).

Using a external power supply something like Quantum battery pack, the full recycle time for a full flash can be fasten up to 3 to 4 seconds!!!! 10 rolls of films is a peace of cake for Quantum!!! However I don't know the performance after 10 rolls or maybe after 20 rolls. Anyway I personally think that 10 rolls per day is usually enough for normal occasions (we are not talking about pro., right???).

Q: Does DOF preview really useful in practical mean? It seem to me that it only darken the screen.

A: DOF preview is important to me. Without it, I can hardly find the right spot to focus in Macro Photography. Forget about the DOF for Macro Calculation. DOF preview is the most practical answer. You can see exactly the DOF you are having and focus exactly the right point to maximize the DOF you needed.

Q: Talking about sharpness, I usually came across the word MTF. May I know what is MTF?

A: MTF stands for Modulation Transfer Function. It is a measure of 'sharpness' of an optical system. Basically you input a square wave signal (pattern of black and white bands with "perfectly" sharp edges). You measure the results after passing through the optical system and you get a sine wave. The closer the sine wave is to a square wave the higher the MTF (described as a percentage so 100% MTF, no degradation, 0% MTF all you get is flat gray from your black & white stripes).

Bill Gillooly

Q: Slides or Prints?

Answer 1

I prefer slides for three reasons.

1. When viewing in a group, slides allow common visual experiences. Everyone sees the slide the same time. If the same group were viewing prints, each would be looking at a different images.

2. When I started shooting, most magazines wanted slides submitted for publication.

3. Slides are easier to file.

Bruce Lane

Answer 2

Serious color photographers are shooting color for the following reasons:

1) If you want to have your photographs purchased and published at some point, the publishing world is geared toward slides. Slides are generally all they want to use for their publications...although digital files now have a presence.

2) Slides have better contrast and color saturation than negative film.

3) As you've discovered, it is easier to view, sort, and file slides, because there is no resulting print (for viewing the color) that needs to be filed with it. It is nice to view slides on the light box through the lupe and toss the individual crap images directly in the trash.

4) Processing is cheaper. Unless you instruct a color lab not to, they will print every frame. You pay for processing and the price per print. Remember, though, that most labs will make you a contact print of your color negs, upon request. They'll print the negatives flat against an 8x10 sheet of paper, whereupon you can view the positive (color) image of your negatives and then pick out what you want printed. You can then hole-punch this sheet and file it in a binder with your negative file.

Any advantage to negatives?

The only significant advantage I can really think of is that color negative film has greater exposure latitude than slide film. Slide film does not handle contrasty scenes as well as negative film. I believe the figure for slides is a five stop range and more like eight stops for color negatives. This gives you more margin for error.

Having prints made is more convenient with color negs, but it can be tricky to get consistent results from the lab.

There is nothing that matches the color of a slide printed directly (no inter-negative) with either a Type R process or Ilfochrome. Even using an internegative, results can be stunning. The colors seem much more vibrant and true than anything you might get from color negative film. I like to use The Slideprinter in Denver, Colorado or FinePrint, also in Colorado (Fort Collins). I do not have their phone numbers handy but you can look them up in the 303 area code. Other list members will probably send a flurry of suggestions for good printing firms.

I just went down the street the other day to one of Tom Mangelsen's Images of Nature galleries. An employee there tells me that Tom often uses FinePrint. For many of his large prints, they will create a 4x5 internegative for the print and print them HUGE. I couldn't believe my eyes! I thought for sure this stuff was originally shot with at least a medium format camera, but it was 35mm. Obviously, he knows how to take sharp images in the first place, but the results were really spectacular.

Weiser

Q: I've got a newly bought EOS-5. I still have an old Olympus T-32 flash, which is still an excellent flash in its own right. Can I use it on my new EOS-5 ??? Or is it a big no-no ??

A: I had tried using a Minolta TTL flash on my A2 and every things is fine. Of course you loose the TTL function, that's all. However I am uncertain about other model flash on other system.

Q: Computing distances / Zoom for wildlife???

A: Use similar triangles. One triangle is: Center of lens, center of negative, edge of negative. Other triangle is: Center of lens, center of subject , edge of subject. This uses half the width of negative, and half the width of subject. If you double both, you get the formula:

w/d = n/f

where w = width of subject,
d = distance between lens and subject,
n = width of negative,
f = focal length of lens.

If you know three of the numbers, you can solve for the fourth. In the example above, we have w/200 = .036/.3, so w=24.

Nice to know when deciding what lenses to take...

Mark

Q: Tamron28-200 vs Sigma28-210

Help - I'm purchasing one or the other and getting conflicting advice from the New York mail order companies. Any advice re ease of use, reliability, results, etc? Two of the companies have told me the Sigma is better (at $20 more).

A: Optically they are about the same, The Sigma is a bit bigger with hood,both focus over the same range, and take the same size filters. However the Sigma in terms of mechanical design I can only describe as USER HOSTILE.

I purchased a Sigma 28/200 to use with my A2E for travel a few years ago. After a few weeks of use it came up with a new feature, about every 30 or so frames, it would lock the zoom ring just after exposure. The only way to release it was to reset the camera (turn off body), yet there should not have been any connection mechanically between the firing of the shutter and
the zoom system. During time exposures the lens could be zoomed freely while shutter was open. And with the zoom locked, I could still take photos, and it worked otherwise normally as a fixed length lens.

So... That lens was returned to the camera store for another of the same type. This one did not the same problem, no... It had to develop it own idea... When the camera was turned for vertical format shots, the zoom was first tight, then after a week or so, would not move over the 100mm (or there abouts) point.

This one went back to the factory rep. as the store was tired of my problems. They reviewed it said it was an unfixable factory fault, and gave me my money back. I purchased a TAMRON 28/200 (I now own two of them) and they both work without any problem and have thousands of shots taken with them.

Another think I hated about the Sima (a user Hostile feature) is that to make the lens a bit shorter, they mount the filter on the lens shade ring, not on the lens itself. Thus if you remove the lens shade, the filter leaves as well. I had purchased a spare hood assembly and removed the rubber hood so I could use my PL filters. (this added about $45 US to cost) And when inside and using the built in flash of the camera, you again have to remove the lens hood, but so does your protective filter. Think about
it, a naked lens front, and a children's party. that poor front element.

My suggestion, Look at the new Super version of the Tamron 28/200, this not only has the performance of the originally, but the filter not longer rotates during focus, and it will now focus much closer than the original 6 feet (Sigma was same, about 6 feet), If not that, then go for the normal original Tamron. as an aside, Pentax likes the new Tamron so well, I understand that they simply put their name on it and sell it as one of their own.


Edward Agnew, P.Eng.
Agnew Technologies

Q: Difficulty of autofocus at night. Any solution?

A: Here are a couple of tips that I use when faced with focusing problems at night. I'm assuming that you were talking about human subjects!!

1) Set the distance manually on the lens.
2) Look for something contrasty on your subject such as a white shirt against a dark jacket and focus on that.
3) Ask you subject to hold a light object (i.e. a cigarette packet or piece of paper) against their chest and focus on that.
4) Ask your subject to light a match or a lighter and focus on that.
5) Use a small torch (I use a mini-maglite) to shine on the subject.

Hope these help.

Tom

Q: BTW, how to make the flash from the flash look more natural??? Any comment and suggestion would be appreciated, thanks you.

Answer 1

It seems like you are talking about several different picture taking situations. Flash can only be made more natural by diffusing it; the size of the light source determines the quality of light, i.e. the bigger and broader the source, generally the more diffuse it is.

You can

(1) bounce it off the ceiling or wall (assuming the ceiling or wall is not too far away and is neutral or white colored)

(2) you can fire the flash into an umbrella thus spreading the light out (and reducing its intensity by one or two stops)

(3) you can fire the light source through translucent material.

I think a flash meter is almost essential to determine the amount of light reaching the subject.

Doug Clifford

Answer 2

For less blasting flash you might want to either bounce the light off the ceiling or other handy surface - however, the light that hits your subject will take on some of the color (if any) of the surface being used (you'll need a flash head that tilts, etc). As an alternative you might want to look at LumiQuest's line of soft boxes, that attach directly to your flash head and both enlarge the light source and soften it. These sell for between US$18 and $30 at B&H (www.bhphotovideo.com). Sto-Fen and The Shell products are similar ideas.

I have and use the LumiQuest products and get very good results. I've not tried the others.

Of course, the VERY best softening will be provided by bouncing the flash off of an umbrella. This will enlarge your light source to the diameter of that umbrella and provide very soft-edged shadows.

Bob Brown

Q: Opinion on Tamron 28-105 2.8 SP.

Answer 1

I shot a few pictures with the Tamron 28-105 f2.8 a couple of weeks ago in Yosemite, and was pleased with the lens. Unfortunately, the Tiffen circular polarizer that I bought with the lens was defective, and gave me very blotchy blue skies, but the lens performed well. Here are my first impressions:

It has a very solid feel. It is larger and heavier than it's predecessor, but has several advantages. First, the focus is faster and quieter than the old 35-105. The focus motor has two speeds, a fast speed to get the lens close to the right distance, and then a slow speed to fine tune the focus. The fast speed is about half as loud as the old lens, and sounds smoother; and the slow speed is virtually silent. The old lens had only one speed, and often left you wondering if the final focus was right on. Not so with the new lens. There is very little hunting, although occasionally it hunts from end to end. (I think this is the fault of the
camera (Elan IIe) rather than the lens.) The internal focus is a tremendous improvement. No more fiddling with the filter after
refocusing. The zoom ring is large and grippable, and has a very smooth positive feel.

If you push forward on the zoom ring, it snaps into the high friction position. It takes enough pressure to switch between positions that accidental switching would never be a problem. The auto/manual switch is in a convenient location and is easy to use. The lens seems very sharp. At 105mm, it seems sharper than the old 35-105. In fact, with a Tamron 1.4X converter, it still appears sharp. The close focus abilities of the lens are tremendous. The focus distance of 19.6 inches is actually
from the film plane to the subject, which was a surprise to me.

The lens is both wide enough and long enough that, if space and weight are a concern, I only need to carry one lens and a converter to get 95% of the shots that I want. So far, I'm thrilled with the lens.

Q: How is the Tokina 100-300ATX? Can it be Canon 100-300L alternatives?

A: A N**** user who traded his N**** 80-200/2.8 + 1.4TC for the Tokina was so friendly to send me some tests
slides.

The results were DISAPPOINTING! Compared to some of my 100-300L slides there was an overall lack of contrast. Sharpness was worse too, but not so obvious. Overall no serious option for a replacement.

Q: I need to urgently take photo's from a TV screen. Any clues as to how to go abt it.

A: I suppose you are shooting negative.

Negative
=====

- Mounted your camera on a tripod (used cable release)
- use slow film, ASA 100 (example, Reala)
- shutter speed slower than 1/30 (flicker free) / must be slower than your TV's vertical refresh rate.
- use lens longer than 100mm (to avoid distortion)
- overexposed it over 1/2 to 1 stop (for safety)
- make sure your room where the TV located is dark enough (avoid reflection and increase contrast)
- fine tuned your TV's color, contrast and etc. (make sure black is black by controlling your TV's brightness)
- Get a good lab to correct the color. (The color capture will be difference from normal shooting)
- Don't expect too much (cause the resolution is low and etc)

Q: Why is 35mm film referred to as '135' film?

A: This is historical. It comes from the numbering scheme that evolved at Kodak for distinguishing between different types of roll films. There are several web sites with this information. The one I dug up to answer this question is: http://www.ghg.net/mangum/Kodak/kodak.html . I'll refer you there to get the complete text. The following excerpts are from the document at the above URL.

Kodak Roll Films Starting with 101

It first became necessary to specify which Kodak roll film was required with the introduction of the No. 2 Kodak camera in 1889. As different models and sizes of cameras were introduced, the film boxes were marked with the names of the cameras that the roll would fit.

By 1908, this system had become difficult to use for ordering film. It was now necessary to specify the image size and the camera the film was to be used in, as not all films for the same size pictures could be used interchangeably. To simplify this system, it was decided that the daylight-loading roll films on flanged spools would be numbered in the order of introduction, starting with the first Kodak film of this type introduced with the No. 2 Bullet camera in 1895 as number 101.

<snip>

35mm

In 1916, a very small box camera named the No. 00 Cartridge Premo camera was introduced using a No.35 roll film. This was numbered differently as it was not the same as the Eastman Non-Curling film supplied in the other roll film sizes but was apparently made from unperforated 35mm motion-picture film. In 1934 when 35mm film in cartridges were introduced with the Kodak Retina camera, number 135 was assigned to this product. This film size could also be used in the Contax and Leica cameras. Daylight-loading spools of film for these two cameras were also offered, and were numbered 235 and 435. In July 1952, a special length of film for 20 pairs of pictures made with 35mm stereo cameras was introduced and designated as 335.

Hope this helps.

Wayde

Q: How long can film last?

Answer 1

I assume you are talking about COLOR negatives ? I have black and white negatives in perfect shape from the 1930s. I recently printed some color negatives I shot in 1976 in Mexico and they don't seem to have changed much..... Kodak material.

Those same negatives were shot from September 1976 to April 1977 and didn't get processed until June 1997..... and only one roll of 12 exposures out of 6000 images was 'spoiled'.

William Scanlon

Answer 2

A: Processed negatives or slides should last for years when stored under the proper conditions: in the dark, dry, and cool (approximately 68 degrees Fahrenheit or less)

Exposed film should be processed as soon as possible because, if anything, the latent image (the undeveloped image) is more fragile than the film itself. Silver salts that have been affected by light are in a very delicate state, photochemically speaking. An exposed, but unprocessed, image may last a week or two, maybe even a month without deteriorating, but I wouldn't risk any more than that, even under ideal storage conditions. I've seen even old Kodachrome images deteriorate as a result of waiting
before processing.

I don't know about the vacuum bit you've been told, but certainly films are prepared under clean-room conditions under highly controlled climactic conditions as well. Mainly this means that film vendors try to eliminate dust and other particulate matter and they try to keep the film dry until it's put into it's foil wrap or plastic canister packaging--these offer significant protection against moisture and humidity. I believe there used to be "tropical packs" of film headed for those climates. I don't know if
this is still done or if modern packaging obviates the need for it.

I hope this answers your questions.

Howard Dinin

Answer 3

Maybe you are referring to changes detectable only in laboratory conditions, because I've developed color negative film stored at ordinary room temperatures 6 or 7 years after the exposures were made, and obtained perfectly printable negatives. There were no obvious changes visible to the naked eye.

I routinely develop B/W negatives months after the exposures were made, again with out any noticeable effects.

Dan Cardish

Answer 4

> But how cold is acceptable? Will the film surface begin to 'crack' at very low temperatures?

This question has been addressed is great detail by a conservator for the Smithsonian, Mark H. McCormick-Goodhart, in "The allowable temperature and relative humidity range for the safe use and storage of photographic materials", Journal of the Society of Archivists, V. 17 No. 1, 1996, pp 7-21. Though this particular paper addresses processed film, I believe the issues are identical for unprocessed film (whether exposed or not) as well.

The primary constraint is differential expansion of the emulsion and base layers. This paper makes 2 primary points:

1. In a sealed enclosure with relatively low air volume, the humidity will decrease with decreasing temperature, because the emulsion absorbs a small amount of moisture from the air to maintain equilibrium.

2. So long as the package is sealed, and the humidity at equilibrium is within specified limits, the temperature can be increased or decreased within a wide range any number of times without causing damage.

The limits he recommends on temperature are -25C to +25C. His lower limit is primarily because there is little advantage to going lower. The upper limit is constrained by both the glass transition temperature of gelatin, and concern about simple stability of the chemicals involved at elevated temperature. If you really want to exceed either, particularly the upper, with a sealed film package, you definitely need to see the whole paper.

At an initial temperature of 20C, the humidity at equilibrium should be between 35% and 60%. If you seal your film, once it has had time to reach equilibrium within this range, you can freeze it with no worry about damage.

You should *not* freeze film without first sealing it against humidity because the humidity in residential refrigerators and freezers is very poorly controlled. Self-defrosting freezers tend to be very low humidity. Non-self-defrosting freezers tend to be very high humidity.

Though he does not recommend any specific sealing method, most people would probably consider a plastic film can, inside at least a couple layers of freezer bag, to be adequate. I would add some sort of moisture buffer, such as matte board equilibrated to an appropriate humidity, in each bag for safety's sake. I might also add a humidity indicator card to the outer bag so I'd have a bit of warning in case of a problem, particularly if I was storing the film for an extended period of time in a non-self-defrosting freezer.

The thing you must *avoid at all costs* is allowing the film to equilibrate to a high relative humidity at low temperature, and then raising the temperature. The gelatin becomes very soft if you exceed the glass transition temperature, which can be quite low. At 80% relative humidity, for example, Tg is below 10C. If you allow your film to equilibrate to 60% relative humidity at -25C, then warm it to room temperature, you *will* exceed the glass transition temperature unless you keep your house an awful lot colder than I do mine.

For anyone interested in this issue, I would strongly recommend getting a copy of Mr. McCormick-Goodhart's paper. It is a *very* useful reference. It may be a bit difficult to find in the US other than through inter-library loan, since the JSA is a British
publication. It is well worth the effort and expense.

> Are household freezer temperatures acceptable?

My refrigerator is set about 35F (2C). This puts the freezer very near 0F (-15C). I consider that acceptable. If I planned to store the film for 500 years before using it, I would not.

> How about unexposed film? Is it similar to processed film?

I believe the issues are the same, but I have no references or experience to back this up.

Regards,