Need a little help with some magnification math per bellows

[JBW]

Thanks. There certainly are many ways to cook a chicken

[xpatUSA]

Here are a couple of "macro" setups just to illustrate that almost anything is possible:-

Pentax K10D with Praktica M42 bellows and TT&H f6.3 six inch anastigmat.

Excellent rigs, especially that last one with it's 3D look. For some reason my brain has the impression of a steam locomotive . . .

You forgot the AF switch.

[GrahamS]

You forgot the AF switch.

Damn!!!! I wondered why it wouldn't focus......

[DanK]

Brian,

I would give you much the same advice as Grahame. I don't know the effective FL of your Tamron at minimum working distance, but in round numbers, a full set of Kenko tubes (68 mm) will give you around 2:1. That is (1) enough for fairly dramatic closeups, and (2) a lot harder than 1:1. If I were in your shoes, I would stick with the simple solution of tubes until you get both comfortable with that level of magnification and you find that you are still frustrated without having higher magnification.

Keep in mind that the decreasing DOF will be a real limitation. If you want reasonable DOF, higher magnification makes stacking even more important.

One thought about Grahame's comment about FF vs. crop: I think the answer is "maybe." A crop will give you a narrower angle of view, so comparing the subject with the frame, it will look more magnified with a crop, but it isn't really. If a FF has the same pixel density as a FF, cropping the FF image will give you the exact same number of pixels on the subject. However, in many cases, crops have higher pixel density, so even though they don't give you more magnification, they do give you more pixels on the subject.

Dan

[Stagecoach]

Brian,

One thought about Grahame's comment about FF vs. crop: I think the answer is "maybe." A crop will give you a narrower angle of view, so comparing the subject with the frame, it will look more magnified with a crop, but it isn't really. If a FF has the same pixel density as a FF, cropping the FF image will give you the exact same number of pixels on the subject. However, in many cases, crops have higher pixel density, so even though they don't give you more magnification, they do give you more pixels on the subject.

Dan

Agreed Dan, that is what I meant, without getting into the pixel density. The 'lens magnification' remains the same whether being used on a FF or Crop but the smaller sensor size of the crop gives the 'result' of the subject appearing larger in the frame.

[george013]

Agreed Dan, that is what I meant, without getting into the pixel density. The 'lens magnification' remains the same whether being used on a FF or Crop but the smaller sensor size of the crop gives the 'result' of the subject appearing larger in the frame.

But when viewed a same frame on the same size, the FF will be sharper. I think.

George

[DanK]

But when viewed a same frame on the same size, the FF will be sharper. I think.

George

Do you mean with or without similar pixel density? With similar pixel density and assuming the same sensor technology, the images should be identical regardless of sensor size. Assuming greater pixel density in the crop-sensor camera (again, assuming similar sensor technology other than photosite size), why would you expect greater sharpness from the FF image? If greater pixel density reduces sharpness, why are people buying FF cameras like the D850 or 5DS? At small enough display sizes and minimal cropping, it should make no difference, but at larger sizes or with substantial cropping, it will: greater sharpness with more pixels.

The reason some people argue for using FF and cropping is because in many comparisons, the sensor technology is not identical, and they argue that the higher-quality data from the larger photosites offsets the lower level of detail. Someone on this site recently posted that, but I don't recall whom. I haven't tested it myself, although I could with my 7D and 5D III.

[xpatUSA]

One thought about Grahame's comment about FF vs. crop: I think the answer is "maybe." A crop will give you a narrower angle of view, so comparing the subject with the frame, it will look more magnified with a crop, but it isn't really. If a FF has the same pixel density as a FF, cropping the FF image will give you the exact same number of pixels on the subject. However, in many cases, crops have higher pixel density, so even though they don't give you more magnification, they do give you more pixels on the subject.

Dan

Some might find that confusing, Dan, IMHO.

Did we perhaps mean "in many cases, crop cameras/sensors have higher pixel density"?

Please pardon my pedantry as usual.

[Stagecoach]

But when viewed a same frame on the same size, the FF will be sharper. I think.

George

George, for clarity my post 14 on this thread has absolutely nothing to do with FF Vs Crop, my example of the dragonfly pic is simply an 'example' of the type of 'magnification/finished image subject sizing' Brian can get with his setup with his Crop camera when using the macro lens he owns.

What you "think' regarding the sharpness of FF Vs Crop has no relevance to Brian wanting to increase 'magnification' with his camera and lens.

[george013]

Do you mean with or without similar pixel density? With similar pixel density and assuming the same sensor technology, the images should be identical regardless of sensor size. Assuming greater pixel density in the crop-sensor camera (again, assuming similar sensor technology other than photosite size), why would you expect greater sharpness from the FF image? If greater pixel density reduces sharpness, why are people buying FF cameras like the D850 or 5DS? At small enough display sizes and minimal cropping, it should make no difference, but at larger sizes or with substantial cropping, it will: greater sharpness with more pixels.

The reason some people argue for using FF and cropping is because in many comparisons, the sensor technology is not identical, and they argue that the higher-quality data from the larger photosites offsets the lower level of detail. Someone on this site recently posted that, but I don't recall whom. I haven't tested it myself, although I could with my 7D and 5D III.

Just the viewing size. The coc. You've to enlarge the crop image more as the ff image to fit on a A4 or a screen.
There're more legitimate reasons to choose for crop or ff .

Optical, for lens designers, the magnification might be important. But as a photographer I want a result different from 24x36 or 15x24mm print. Let's say a A4, or a monitor screen.



George

[DanK]

You've to enlarge the crop image more as the ff image to fit on a A4 or a screen.

You missed the content of the earlier posts. The issue was cropping the image from the FF to the same size as the image from the crop sensor, so the magnification to any print size is identical.

[Stagecoach]

You missed the content of the earlier posts. The issue was cropping the image from the FF to the same size as the image from the crop sensor, so the magnification to any print size is identical.

No it was not Dan, as far as my postings.

I used the FF because I had it out at the time and put a 36mm tube on the 105mm (near enough Brians 90mm) which gives roughly the same picture result as if I had used a Crop camera without the tube.

The image No 2 was simply an example of how I would/could 'crop' in post a reasonable amount to make the critter look even bigger. Exactly as Brian would have been able to do with his lens/camera for producing pictures for viewing at screen/web size.

[xpatUSA]

The reason some people argue for using FF and cropping is because in many comparisons, the sensor technology is not identical, and they argue that the higher-quality data from the larger photosites offsets the lower level of detail. Someone on this site recently posted that, but I don't recall whom. I haven't tested it myself, although I could with my 7D and 5D III.

I have tested it many times Dan. Some of my cameras offer true on-sensor binning 2x2. For example, 4704x3136px (5um photo-sites) or 2336x1568px (10um) are available from the same camera/sensor.

Canon s-raw is similar?

It turns out that, for the same target shot and all other things being equal, the lower 'pixel density' gives greater sharpness every time ... but on a cycles per pixel basis.

Sigma's on-sensor binning, by definition, provides the average of four pixels. That averaging provides less noise /sqrt(2) and is the equivalent of bi-linear down-sampling.

Since there are "better" down-sampling algorithms, e.g. Lanczos, I can usually get a slightly "better" image by shooting 1x1 (no binning) and re-sampling as required in post.

[rpcrowe]

Alan,
I spent an enjoyable hour or so perusing the Goodwill Site and (much to my spouse's glee) didn't purchase anything. But as Douglas MacArthur said "I SHALL RETURN!"

[GrahamS]

This is taken with a Pentax K10D fitted with a PK - M42 mount adaptor (no extension) and a Carl Zeiss Jena Flektogon 35mm f2.5 prime lens. No extension tubes, close up filters, 'nuttin! Exposure was f11 @1/40th ISO400. No noise reduction has been applied in post and this is the entire frame.