I couldn't help it
found a yashica fx3 with a
28-50mm super paragon pmc auto zoom 1:35-4.5
70-180mm Mitakon mc zoom 1:4.5 with macro

both lenses seem in mint condition but are they any good?

Old is a state of mind :)

The benefit of 16 bit values is precision when you process an image your performing mathematical operations.
when you produce the final image the 8 bit values are good enough. if you process in 8 bit the values can drift off a bit.

while not exactly the same (but easier to think about) if you add 3.6 and 4.5 with integer maths then the answer is 7 with floating point the answer is 8.1 so the proper value is closer to 8 than 7
multiplication 3 x 4 is 12 but 3.6x 4.5 is 16.2 the next math you do on the results will drift even further apart.
so as you can imagine if this was pixels some values will be pushed higher some lower and the end result is a bit of a mess. by working with a higher precision then the end values will be closer to what they should be. As the 8 bit conversion only happens right at the end. does that help?

May I ask what software you are using to convert the negative ?

After testing out various raw processing programs I found that most prefer to work on their own version of raw. However Digital Photo Professional from canon will open a tiff file and process it otherwise you are stuck processing jpegs.

By using ufraw to convert from DNG to TIFF format the Canon Software is able to produce good results fast. Some versions of the Pentax software can handle DNG. Nikon is only working with NEF and charges you for the privilege and Hasselblad didn't like my graphics card so kept crashing on my system.

Digital Photo Professional is the most useful without a doubt.

If you want to mess up an sd card remove it while its in the middle of writing. Doesn't matter if its in the camera or in the computer. Generally its easiest to break it in the computer as it caches the writes to the card pulling it out before the computers finished working with it tends to mess with the file record. You can break usb devices this way too. which is why you should eject a card and wait till it says it is safe to remove. Sometimes you just lose data sometimes you lose all data. sometimes its not even possible to reformat it and make it usable again. If you do rescue it within a couple of weeks it tends to fail for good. If the file system is stable and it hasn't got any pending writes. Then you can yank it out and get away with it most of the time but don't make a habit of it or you will break it.

there is a third option try the manufacturers software.
the problem with the in camera option is it finishes with a jpeg which may or may not be acceptable.
if you go from raw then you need to reproduce those steps again or something like.

pretty sure you could get the manufacturers software to reproduce the jpeg image on the pc rather than the camera and then you can continue the post processing from that point instead of starting from scratch. with the added benefit that the raw information hasn't been thrown away yet.

It might even be possible to cross process using canon software to process a nikon image. I think Hasselblad has their software for a free download for example.

Why start from scratch when the jpeg is mostly as you want it?

That indeed is an interesting effect Larger sensor sizes can use smaller apertures before the diffraction airy disk becomes larger than the circle of confusion.

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

It might seem a bit counter intuitive but the more pixels in a given sensor size the closer the pixels are to the airy disk size. But why do I have an f-stop of 22 on my camera lens? Well the largest sensor on a 35mm camera is film and at f22 the airy ring size is just about starting to create diffraction effects.

Medium format camera's can go even smaller without diffraction. Compact camera's with their tiny sensors are even more sensitive to diffraction than DSLRs resulting in most being limited to f8. One more positive for 35mm DSLR but remember that medium format camera can do better! Plus with tilt and shift they can correct the distortion that you get when photographing buildings for example.

quality of the lens makes a pretty big difference if your 300mm was prime it could well be better than your zoom 15-85mm when your looking at sharpness.

However depth of field is related to focal length and shorter lenses have greater depth of field at closer distances than longer lenses.

e.g 300mm at 5meter subject distance has a dof of 8cm 4.96- 5.04 at f8 with the dof getting smaller as you open up

with the subject at 5 meters and f8 at 15mm dof is from 1.1 meters to infinity
at 1 meter and f8 dof is from 59cm - 3.34 meters. (used a depth of field calculator for these figures)

Perspective this varies with focal length. Shorter lenses take in a wider field of view than longer lenses. http://imaging.nikon.com/history/basics/19/03.htm there are a series of images at this link where the subject size in the frame remains the same by varying the distance between the camera and subject.

what is interesting is what happens to the background at a short focal length the distance between the background and the subject appears large and you see the whole of the building as the focal length increases you see less and less of the building which you expect, short lenses have wider fields of view than long lenses. However the other effect is that the building in the background seems to move nearer to the subject the longer the focal length of the lens.

You can also see the difference in depth of field with the short focal length the background is much more in focus than with the longer lens. Which focal length you choose depends on what you are trying to photograph. With the shorter lens you have a better view of the location of the subject and as the focal length increases the location becomes increasingly anonymous.

Another thing to notice is the effect on the subject. At the short focal length in these pictures the girl appears quite slender, at the longer focal distance she appears to be a lot more chunky. The shape of her face goes from distinctly oval to quite round. From possibly anorexic to chubby if not a bit obese.

It looks like the shorter lens is the winner here, sharper better sense of place, the subject looks slender and attractive. However if the subject was closer to the camera her nose would begin to grow out of proportion to her face. So a longer lens would balance her facial features better.

Taking a photo of a dog on the other hand with a short focal length lens close up gives a huge nose and a better sense of fun and personality. Longer lenses give a better sense of dignity and poise in the dog. The dog doesn't mind looking a bit of a clown, but your girlfriend or wife will prefer to look in proportion and possibly a little bit thinner.

finally there is always cropping you can get the shape you want for your model with the shorter lens and crop out more of the background giving a slender look to your subject and and making her the focus of your photograph.

Probably best to use the lens quite open to decrease the depth of field but not so much as to lose sharpness on your subject, then the background will be nice and fuzzy with your subject looking a pleasing shape and sharp.

unfortunately wide open the lens is sharpest at the centre and soft at the edges to counter that you close down to the sweet spot but your dof will be greater. To counter that you may have to consider a more expensive lens...

Interesting question which opened up the creative side of photography, sorry for meandering but have a look at the images on the nikon page and see what you take from it.

what a mess make them fractions 1/1 1/2 1/4 1/8 1/16 (cant be bothered with the stops in between but each stop is half or double the area. unfortunately its 1 / root of the area so 1/2 is actually a 1/4 of 1/1 and 1/4 is 1/16th of the area of 1/1 ect.

The maths isn't really important just the stop and that if you half the area it will double the time for the same exposure or if you want to keep the same time then double the iso. this is why iso's are usually 100 200 400 800 and speeds are 1 sec 1/2 1/4 1/8 1/16 1/30 1/60 1/125 1/250 the timing drifts off for convenience but fstops 5.6 and f11 are not accurate figures but ball park ones. good enough values for small dials

focal length is made pretty much irrelevant by the f number so if an exposure on a 50mm lens was say 1/125 at f4 with a 100mm lens its still 1/125 at f4 which is nice. The actual physical hole size doesn't matter we don't need to know that.

I think the pentax software does too, but I haven't tried it out, if it has the option to save as tiff or similar then it could be a useful intermediate step prior to using photoshop ect. Even if all you want is to crop you will be decompressing and recompressing the jpeg file a second time which is bound to lose a little more information. I guess you can prove it if you checksum the original jpeg open and save it again with no other operation in between. if the checksum is different then you must have a slightly degraded image. kind of like taping a cassette tape.

This topic has made me think there should be a third way.
your camera produces a good jpeg but you can't tweak that jpeg as well as you can with raw.

if you start with raw you lose the processing that the camera did to get that nice jpeg, leaving you to try and reproduce those by hand.

as a house analogy we get from the camera a house or a foundation. If you like the house but want to change the gutters. we demolish the house rebuild from the foundation to try and get a very similar house but with different guttering. Unfortunately the windows may be a bit wonky now ...

I think there may be software from the camera manufacturers which can let you produce the jpeg on your computer the same way as the camera processes the raw file but then lets you change the ending so to speak.

It'd certainly be nice to be able to reach the jpeg image stage without then cutting it down to 8 bits per channel and compressing it.

http://en.wikipedia.org/wiki/Portable_Network_Graphics#Comparison_to_other_file_formats

Interesting read about png, it was initially developed to replace gif which was patented till 2003 because of the compression used. gif only had 256 colors. Since then png has become much better than gif or jpeg with support for transparency, which makes web pages look better, but without support for animation, which makes web pages look worse.

Png has grown a lot since its original conception and can handle as much as 64 bits for 4 channels of 16bit rgb and alpha (transparency). It's worth noting png support can be partial support, which means you might not get all the features you want. E.g Internet Explorer has issues with PNG files up to and including version 9.

It's probably worth looking at the link and the comparison with other file formats, especially if you have been around a while. thoughts of no it doesn't may turn in to no it didn't, if like me your knowledge has become a little out dated. There are lossless jpeg formats too :)

It's maths folks, an 8 bit colour has values between 0 and 255 and a 16 bit images has 65.535 values lets look at it in binary 1111,1111,1111,1111 is the highest 16 bit and 1111,1111 is the highest 8 bit number to convert a 16 bit number to 8 bit just chop off the 8 least significant bits so giving 1111,1111 convert it back to 16 bit and its 1111,1111,0000,0000 you might make it 1111,1111,1000,0000 as that would be half way between but lets not worry to much about that the jpeg compression probably messed things up worse than that. you can never get that information back.

However if you are going to be performing a series of mathematical operations then errors will be multiplying.

each result in an 8 bit calculation can only be precise to 8 bits where each calculation in 16 bit has 16 bits of precision. After a few calculations the 8 bit value manipulated in 8 bit will be further off than the same 8 bit value manipulated as a 16 bit number.

so obviously a 16 bit image manipulated with 16 bit precision operations will be superior to the same image reduced to 8 bits and manipulated with 8bit precision operations.

but what of an 8 bit image converted to 16 bit and then manipulated with 16 bit precision operations? can it be worse than the 8 bit operations well possibly but it could be better since each operation will be more accurate in the least significant bits. the intermediate values should be closer to what they should be.

You can't reclaim lost information which everyone has been saying. but I think there is an argument that you can reduce further loss by working in 16 bits rather than 8 bits.

Worth a try , your doing it wrong , but you might get a better result.

Usually it's shipping which can be problematic with hongkong and china suppliers. China is generally slower than HK. I've had delivery times of between 7 days and 2 months.

I don't think you can blame the supplier entirely for that, there is a lot of seasonal variation between delivery times you might get lucky and have rapid processing between stops or it might sit in a warehouse for a week or two waiting for a full load to the next destination. Even insured registered delivery is no guarantee of speedy delivery.

I think my fastest and slowest shipping times were with the same supplier.